Newsgroups: sci.bio.food-science
Subject: Re: E.coli O157 outbreak in Scottish hospital
From: Oz <Oz@upthorpe.demon.co.uk>
Date: Fri, 30 May 1997 12:21:54 +0100

In article <5mmaqj$ijk$1@news.uni-c.dk>, Torsten Brinch <iaotb@inet.uni-
c.dk> writes

>Although there may be indications that food
>hygiene standards have been raised, this has  been done
>often as a _reaction_ to detection of food borne disease.

Speaking from the sharp end it has mostly just been a general tightening
of minimum standards, a bit here, a bit there. None (save for various
eradication schemes) have been a direct result of human infection (in
milk and cereals anyway). Some (in milk) has been due to sporadic low-
level processing problems. It is interesting to note that as a result,
some cheeses, particularly swiss ones, now do not produce the flavour
and appearance (the holes have almost gone) that they used to have. This
even extends to cheddars where the unsanitary farmhouse variety with the
great flavour is now unobtainable.

>But the theory, that reduced regular exposure could lead
>to decreased resistance, is worthy of examination IMO.
>In this case, do we have any indication of acquired resistance
>to O157:H7? The theory could be testable.

If there was an antibody titre test for the bacteria (or it's toxin) it
would only be recessary to sample a few thousand cattle workers compared
to a few thousand central city dwellers.

>It also seems to me, that consumers may have changed their
>food preferences, their food preparation habits, and possibly
>some good kitchen hygiene rules have been weakened.

Yes. In fact absolutely yes.

>OTOH, if the bug or it's spread in herds
>are of a more recent nature, we would have to look for other
>explanations.

That it's just a new strain, in a long line of new strains, is also a
possibility. The fact that this one produces very high levels of toxins
being incidental, but brings it to our attention.

>Change in animal feed patterns?,

To be honest I don't think there has been much change for quite a few
decades. Some areas have only recently switched from hay to silage but
under reasonable circumstances I could expect that to improve
bacteriological status particularly in high rainfall areas.

>the use
>of gut-flora modifying medication (ionophores)?,

Not in cattle. Growth enhancers of all types are banned as far as I can
tell, the last one going rather recently I admit. However it only ended
up with about a 3 year life anyway.

>increased translocation
>of cattle?,

Translocation? Do we mean transportation here?

>upscaling of on-

Not very significant IMHO.

>and off-farm operations in food production?;

True in the UK, at least. The main reason for this has been the sharp
increase in regulations for abattoirs that smaller firms simply cannot
afford.

There has *certainly* been a HUGE increase in convenience foods. These
are very convenient for bacterial growth too if not handled properly,
which I suspect most of the public do not do.

>Don't kill me, I am just speculatively brain storming here.

Please do not tempt me.  :-)

--
'Oz     "Is it better to seem ignorant and learn,
         - or seem wise and stay ignorant?"

Newsgroups: sci.bio.food-science
Subject: Re: E.coli O157 outbreak in Scottish hospital
From: Oz <Oz@upthorpe.demon.co.uk>
Date: Wed, 4 Jun 1997 07:39:56 +0100

In article <x5J8Z+X.jackmowbray@delphi.com>, jackmowbray@delphi.com
writes
>Hmmm... You seem to be suggesting that microbial contaminants (possibly
>pathogens themselves?) are responsible for the desirable characteristics
>in these cheeses.

I think a better word might be 'character'.

>Granted, increased levels of hygiene on the farm and in
>the cheese plant as well as enhanced dairy herd health may very well be
>responsible for the improved microbiological quality of these products, but
>do you really believe that these hygiene issues impact negatively on the
>sensory characteristics of these cheeses?

The problem with the bubbles in Gruyere and Emmental are quite well
known, I think. Vision is a sense, and IMHO these cheeses have lost
quite a bit of character over the last 20 years and are now nearer
edible rubber than they were.

>Do you know if perhaps heat
>treatment of the milk could be responsible for a reduction in the flavor
>attributes of these cheeses?

Actually, I think the manufacturing process for some swiss cheeses
includes a boiling reduction step, so the situation may be less clear
than I have suggested.

>In your opinion, can high quality cheese be
>made from pasteurized milk?

It depends what you mean by quality, I suppose. Quite a lot of cheeses
do rely on fungi (and probably bacteria too) for characteristic
flavours. A complex of wild micro-organisms might well have more
character than specific farmed strains, with a risk that the cheese
might be ruined by a inappropriate growth of an inappropriate strain.

--
'Oz     "Is it better to seem ignorant and learn,
         - or seem wise and stay ignorant?"

From: Oz <Oz@upthorpe.demon.co.uk>
Newsgroups: sci.bio.food-science,alt.cheese,alt.food
Subject: Re: Raw Milk Cheese - Opinions Anyone?!?
Date: Tue, 18 Nov 1997 08:51:27 +0000

In article <64r3a3$qga$1@pulp.ucs.ualberta.ca>, Shauna
<shauburg@gpu.srv.ualberta.ca> writes

>Anyway, my literature search did not turn up any sensory studies about
>raw milk cheese vs. past. cheese preferences.  So, if anyone knows of
>such studies and which journals I could read them in please let me know.

I know of none, but then I am not an expert. However I think a great
deal of the problem arises for the 'speciality' cheeses. Here they are
not mass produced and the flavours are variable. I cannot see how one
can maintain this variability using starter cultures, particularly as a
small producer is unlikely to be able to maintain a microbiological lab
on site. Remember that there are 1000's of cheeses, many (like goat and
sheep) produced in very small quantities.

There is one documented example where improved milk quality was
responsible for a significant change in cheeses. The swiss 'holey'
cheeses gradually lost their holes during the 70's (?) because the gas
producing microbes were no longer present in high enough concentration
to produce them. Selected strains are now added, and the holes are back,
but the cheese no longer has the complex and 'deep' flavour that it used
to have and I now rarely buy it.

I have also observed that cheese bought locally in France tastes
dramatically better than from local supermarkets and incomparably better
than UK supermarkets. Upon enquiring I was told that local cheese was
made differently to 'supermarket' and 'export' cheese. The requirement
for long shelf life (export) resulted in higher salt (for example) and
the shipping of 'unripe' cheeses. French supermarkets required a
moderate shelf life and consistent quality which leads to mass
production of standardised produce, whilst the 'local' cheeses were sold
at higher prices when absolutely ready and were expected to have a short
shelf life and a variable flavour.

In passing it is worth noting (as a non-expert) that decent cheeses
should be brought to room temperature at least 24 hours before
consumption. The effect on the flavour is dramatic and well worthwhile.
The added advantage is that they don't keep long and so must be
consumed.  :-)  I note that proper cheese shops do not properly
refrigerate their cheeses but merely redescribe then as 'mild' to 'very
ripe'!

--
Oz

From: Oz <Oz@upthorpe.demon.co.uk>
Newsgroups: sci.bio.food-science
Subject: Re: Raw Milk Cheese - Opinions Anyone?!?
Date: Wed, 19 Nov 1997 06:44:45 +0000

In article <347342df.4830052@news.easynet.co.uk>, J Ralph Blanchfield
<jralphb@easynet.co.uk> writes

>"When it comes to discussing freedom to make an informed choice, it
>raises the question of what one means by "informed". You can label
>pre-packed cheese "Made from unpasteurised milk" and in the UK that is
>supposed to happen but I suspect does not always happen.

There are almost no unpasteurised milk products produced in the UK. The
various health organisations have pretty well shut down anyone who was
producing them. Those very few left label very clearly since they
require the premium they need for these products. Judging from the
scottish unpasteurised cheese producer who was shut down, went to court,
and was then allowed to continue the clientel of these producers is very
well informed indeed.

>But supposing
>it does, does that constitute the basis for informed choice if most
>consumers do not think of cheese as being in any way associated with
>food poisoning, and do not appreciate the risk significance of that
>description?

Oh, you mean like the labels on raw meat and vegetables.

'Might have been crapped on by birds carrying really nasty pathogens'?

>(Oz, most people know there is a risk in crossing the
>road, and that is really an informed choice.

Really? I doubt it. Very few people have any idea of the risks of
crossing the road and it's relationship to other risks. In particular
the press have no idea whatsoever.

>But most people do not
>know that they are taking a food poisoning risk when eating some kinds
>of cheese)."

Well, I suppose if they can't read or listen to the radio or television
then this is possible.

>Try telling that to the thousands who have suffered illness and the
>relatives of the 95 who have died, in food poisoning outbreaks
>associated with cheese made with unpasteurised or improperly
>pasteurised milk.

Come on Ralph. Over what period, due to what foods, were they confirmed
or suspected and how many died on the roads during that period?

>Don't you know that responsible food manufacturers are in fact already
>beginning to give label warnings about the presence (or even possible
>presence) of major serious food allergens in their products?

'This product may contain nuts'.

Hmm, I know of newsgroups that should have this warning. :-)

>They also
>recall products that have become cross-contaminated with allergens
>used in other products in the same factory.

Seems a waste of resources where a sticky label would be as effective.
:-)

>They do these things (a)
>because it is a responsible position to take on what is now recognised
>as a food safety issue and (b) as a measure of self-protection.

Mostly the latter. Mostly because UK law is drifting to the position
where it's the fault of whoever is the richest. Usually the insurance
company.

>I assume you mean "prevent". This will only work in a product that is
>not cooked, if the raw material is free from pathogens.

NO raw material is free from pathogens. People have them all over their
skin.

>Raw milk
>cannot be assumed to be free from pathogens,

Nor can the air we breathe, in fact it isn't.

>so the "strict rules to
>control production" ought to include a step to remove any pathogens,
>i.e. pasteurisation.

Mostly it was done to improve shelf life and remove bacteria from poor
herds in bulked milk that played havoc with the *processing*.

>However, we were discussing freedom of informed choice for consumers
>by allowing them to choose to buy  raw milk cheese if they wish. I
>pointed out that it is only INFORMED choice if consumers understood
>the risk associated with cheese described as "made with unpasteurised
>milk", which most do not.

Mostly, I suspect, they do know the risk. Very low.

Nobody has yet commented on typical supplies of raw milk having a
bactoscan of about 30k/ml, and my comparison with mineral water. I would
suggest this is a very salient point. Why has nobody commented on this?


--
Oz

From: Oz <Oz@upthorpe.demon.co.uk>
Newsgroups: sci.bio.food-science,alt.cheese,alt.food
Subject: Re: Raw Milk Cheese - Opinions Anyone?!?
Date: Mon, 24 Nov 1997 22:09:29 +0000

The post that this is a reply to has not yet appeared on my server (but
came to me via email). However replies suggest it has arrived everywhere
else!

In message <199711240655.XAA43996@quartz.ucs.ualberta.ca>, Shauna
<shauburg@gpu.srv.ualberta.ca> writes

>I actually have my textbook from my foodbourne pathogens course and it lists
>S.aureus food poisoning as one of the most common types of foodborne disease.
>S.aureus foodborne illness is a foodborne intoxication, which means that in
>order for one to get sick the organisms must grow in the food and produce
>enough toxin in the food.  So one would not get sick simply by comsuming large
>amounts of S. aureus in a food; they would only get sick if enough toxin had
>been produced in the food - this explains why one would not get sick from
>sucking a thumb.

It also explains why you don't get sick from drinking raw milk
containing traces of S.a. As to products made from raw milk the lactic
fermentation of yougurt will stop S.a. dead in it's tracks and I suspect
a similar action with cheese, although probably not lactic.

Any products that did happen to grow S.a. would normally be rejected due
to taints and off-flavours.

In fact there is another point worth mentioning. As someone brought up
in the middle of London and reared on pasteurised milk, I could not help
noticing how raw and pasteurised milk behave when left out of the
fridge. Pasteurised milk rapidly smells dreadful and clearly grows a
cocktail of unpleasant bugs. Raw milk rapidly turns into a (quite
palatable) natural youghurt. I have noticed this effect on numerous
occasions (well over 20), although a moment's thought suggets this is to
be expected. The main natural bacteria in fresh raw cows milk is (not
surprisingly) lactobacillae whilst pasteurised milk will become rapidly
contaminated with whatever's going about. Lactobacillae make youghurt
whilst 'whatever's going about' is unlikely to.

I still haven't had any informed comment on raw milk bactoscans of 30
k/ml vs the allowed limits in mineral water (50 k/ml I believe).

--
Oz

From: Oz <Oz@upthorpe.demon.co.uk>
Newsgroups: sci.bio.food-science,alt.cheese,alt.food
Subject: Re: Raw Milk Cheese - Opinions Anyone?!?
Date: Thu, 27 Nov 1997 07:11:56 +0000

In article <depreej.333.000E05A5@lincoln.ac.nz>, "Depree, Jonathan A"
<depreej@lincoln.ac.nz> writes
>In article <w1spwAA5M0e0Ewci@upthorpe.demon.co.uk> Oz <Oz@upthorpe.demon.co.uk>
>writes:
>
>The problem, as I understand it, comes when you make cheese out of the milk.
>What you are essentially doing is starting a race between the lactobacilli and
>the staphs.

Yup.

>The lactobacilli will usually win, but one thing i learned from my
>years of growing cultures of bugs is that they are temperamental little sods.
>They can turn sulky and refuse to grow if its a little too hot, cold, too much
>salt, wrong pH or if you look at them funny.

The initial ratio of quantities present initially is often the most
important. Raw milk contains a majority of lactobacillae (they are non-
pathogenic residents of the milk canals), whilst this is not true when
sterilised since I understand that lactobacillae are particularly
sensitive to heat (and antibiotics). If you have just killed off all the
lactobacillae then he who gets in first, wins (at least for a while).

>Sometimes, for whatever reason,
>the lactobacilli get off to a slow start.

Like they are all dead due to pasteurisation?

>They may well overgrow the staphs
>later, but during that initial few hours the staphs grow and produce toxin
>which persists in the finished cheese. This doesn't happen often but it does
>happen often enough to be significant.

The simple solution would be to add a suitable lactic culture post
pasteurisation just to be sure.

>Mind you, nearly all cases of staph food poisoning happen when the farmer
>delivers perfectly good produce and some idiot at the food processing factory
>or catering firm doesn't wash their hands properly. In these cases pasteurised
>milk that's badly handed is far worse than raw milk. It's worth keeping things
>in perspective.

Agreed. It does illustrate that the urge to have zero pathogens is often
confused with the urge to have zero bugs and these criteria are
sometimes mutually incompatible. Indeed for modern milk of very high
hygeine quality to be made into cheeses it might well be safer without
the pasteurisation process but used immediately and with a lactic
starter added. One would only allow this process in plants with suitable
records and high standards.

It's quite interesting that the rush for improved hygeine has resulted
in a *higher* levels of breakdown in dairy herds with very low TBC's. In
other words when a pathogenic bug does get into the herd the effects are
more devastating than they used to be. IMHO this is because of the
rather mindless ways that raw milk is tested, resulting in poor feedback
to the farmer. In particular I have two gripes:

1) Somatic cell counts. These should be abandoned where TBC's are
available. They are a very poor indicator and result in pointless
culling of older animals who generally are genetically superior.

2) Modification of TBC methodology so as to exclude lactobacillae from
the counts, thus more accurately indicating the pathogen levels in the
milk.

NB Still no comment on bactoscans of 30 k/ml vs mineral water .....

--
Oz

From: john.abel@xtra.co.nz (Big John)
Newsgroups: sci.bio.food-science,alt.cheese,alt.food
Subject: Re: Raw Milk Cheese - Opinions Anyone (long)
Date: Thu, 27 Nov 1997 08:05:50 GMT

depreej@lincoln.ac.nz (Depree, Jonathan A) wrote:

<snipped>
>
>Now that's the kind of post I like to see! Do you think that the difference
>was due to changes in the casein or a different mix of bugs in the ripening
>cheese?
>Jonathan Depree,
>Lincoln University, P.O. Box 84, Canterbury, New Zealand.
>
>Socrates was a famous Greek Teacher who went around giving
>people advice. They killed him.   (school history howler)

My apologies for the delay in replying, but I felt that instead of
relying on my (generally faulty) memory, I should dig my thesus out of
the cupboard at home.

Our experimental design involved cheese being made from milk of the
following heat treatments alongside commercial vats of NZ Blue cheese
made form pasteurised (72oC/15 sec) milk:

48oC for 15s, 18s, 21s
60oC for 15s, 18s, 21s
66oC for 15s

The cheeses were analysed at one day old for coliforms, coag +ve
staphs and NSLAB's (nonstarter lactic acid producing bacteria). And
for fat%, moistue%, Calcium% and pH.

This analysis was repeated at 30 days and 60 days old.

Sensory eveluation was carried out at 60 days old.

One variable was the microbiological quality of the raw milk going in
to  the heat treatment stage. This varied from an average TBC of
30,000, to some days when the raw milk was closer to a TBC of
1,000,000.

Conclusions were:
1. Chemical analysis of the cheese was not influenced by the level of
milk heat treatment.
2. The pH of one day old cheese showed a significant difference with
raw milk heat treatment. THe pH decreased with increasing milk heat
treatment. This was because the lower milk heat treatment left more
non-starter bacteria in the cheese to compete with the starter
bacteria for lactose and so less lactic acid was produced.
3. There were no significant differences in pH at 30 days or 60 days.
4. Coliforms i 1 day old cheese increased as heat treatment dropped.
As coliforms are killed below pH 5.4, there were no coliforms present
in the 30 day or 60 day old cheese.
5. Under-pasteurised cheese milk gave staphs in the 1-day old cheese.
Again, these were not present in any of the 30 day and 60 day old
cheese.
6. The cheese appearence was superior in cheese made from milk heat
treated to 60oC or above. The cheese had a quite yellow tinge in milk
with lesser heat treatment. The yellow comes form the presence of
beta-carotene, always higher in NZ's pasture fed cow's milk that in
the grain fed cow's milk of Europe and America. The milk with a lower
heat treatment went into the homogeniser at too low a temperature to
achieve proper homogenisation, giving free fat in the cheesemilk (and
cheese).
7. The lower the heat treatment, the better the cheese sliced and the
smoother it was. Casein denaturation would definately be a factor in
this.
8. Cheese made from milk heat treated at 45oC and 60oC developed
off-flavours as it matured. This was due to the higher levels of
non-starter bacteria.

Conclusion was that the best NZ Blue cheese was made from thermised
(66oC for 15s) milk.


Email to john.abel@xtra.co.nz (home)  jsa@alpine.co.nz (work)

From: Oz <Oz@upthorpe.demon.co.uk>
Newsgroups: sci.bio.food-science,alt.cheese,alt.food
Subject: Re: Raw Milk Cheese - Opinions Anyone (long)
Date: Thu, 27 Nov 1997 13:49:40 +0000

In article <347d153a.2105530@news.xtra.co.nz>, Big John
<john.abel@xtra.co.nz> writes
>depreej@lincoln.ac.nz (Depree, Jonathan A) wrote:
>
>
>Our experimental design involved cheese being made from milk of the
>following heat treatments alongside commercial vats of NZ Blue cheese
>made form pasteurised (72oC/15 sec) milk:
>
>48oC for 15s, 18s, 21s
>60oC for 15s, 18s, 21s
>66oC for 15s
>
>The cheeses were analysed at one day old for coliforms, coag +ve
>staphs and NSLAB's (nonstarter lactic acid producing bacteria).

>One variable was the microbiological quality of the raw milk going in
>to  the heat treatment stage. This varied from an average TBC of
>30,000, to some days when the raw milk was closer to a TBC of
>1,000,000.

What test was used?

I find it hard to see how you had an AVERAGE TBC of 30k/ml if on some
days it was 1000 k/ml. This would require a lot of days at 10 k/ml. Are
you sure that the average was not 300 k/ml and the range 30-1000 k/ml,
which looks more plausible.

I am most interested in the relationship between TBC and the levels of
NSLABS, particularly as these are quite possibly pathogens (mastitic) or
coliforms. Could you tell us this relationship?

>Conclusions were:

>2. The pH of one day old cheese showed a significant difference with
>raw milk heat treatment. THe pH decreased with increasing milk heat
>treatment. This was because the lower milk heat treatment left more
>non-starter bacteria in the cheese to compete with the starter
>bacteria for lactose and so less lactic acid was produced.

So you presumably added a lactic starter culture. At some point the milk
would have been warmed over 6C for further processing. When was the
starter culture added in relationship to the warming?

I am amazed that even at 1000 k/ml non-lactic bacteria could have
significantly reduced the lactose levels unless the milk had been held
at well over 6C for an extended period or stored for a more extended
period (days).

<Snip, no difference after 30 days in the baceriological status of the
cheese: this confirms the statements of other posters.>

>6. The cheese appearence was superior in cheese made from milk heat
>treated to 60oC or above. The cheese had a quite yellow tinge in milk
>with lesser heat treatment. The yellow comes form the presence of
>beta-carotene, always higher in NZ's pasture fed cow's milk that in
>the grain fed cow's milk of Europe and America.

I am intrigued. Why should this modest heat treatment affect the colour?

>The milk with a lower
>heat treatment went into the homogeniser at too low a temperature to
>achieve proper homogenisation, giving free fat in the cheesemilk (and
>cheese).

This is a process related function. If the homogeniser requires milk at
a particular temperature, shouldn't it have been raised to the
appropriate temperature (preferably with starters added then or shortly
afterwards).

>7. The lower the heat treatment, the better the cheese sliced and the
>smoother it was. Casein denaturation would definately be a factor in
>this.

Is this good or bad? To me it sounds good.

>8. Cheese made from milk heat treated at 45oC and 60oC developed
>off-flavours as it matured. This was due to the higher levels of
>non-starter bacteria.

a) I suppose one person's off flavours are another person's 'exquisite'
flavours.

b) How often did this occur and how was it related to the TBC of the
incoming milk?

>Conclusion was that the best NZ Blue cheese was made from thermised
>(66oC for 15s) milk.

The most reliable, I expect.    :-)

--
Oz

From: john.abel@xtra.co.nz (Big John)
Newsgroups: sci.bio.food-science,alt.cheese,alt.food
Subject: Re: Raw Milk Cheese - Opinions Anyone (long)
Date: Sat, 29 Nov 1997 04:01:32 GMT

Oz <Oz@upthorpe.demon.co.uk> wrote:
>In article <347d153a.2105530@news.xtra.co.nz>, Big John
><john.abel@xtra.co.nz> writes
>>The cheeses were analysed at one day old for coliforms, coag +ve
>>staphs and NSLAB's (nonstarter lactic acid producing bacteria).
>>One variable was the microbiological quality of the raw milk going in
>>to  the heat treatment stage. This varied from an average TBC of
>>30,000, to some days when the raw milk was closer to a TBC of
>>1,000,000.
>
>What test was used?

Standard Methods Agar incuated at 30oC for 72 hours.

>I find it hard to see how you had an AVERAGE TBC of 30k/ml if on some
>days it was 1000 k/ml. This would require a lot of days at 10 k/ml. Are
>you sure that the average was not 300 k/ml and the range 30-1000 k/ml,
>which looks more plausible.

We had 1 day at 1,200,000/ml . All other days were below 30,000/ml.

(As an aside: this work was done in 1983. Standards of on farm hygiene
have improved markedly since then. The 480 farms supplying my current
company consistently average TBC of <5,000 /ml)

>I am most interested in the relationship between TBC and the levels of
>NSLABS, particularly as these are quite possibly pathogens (mastitic) or
>coliforms. Could you tell us this relationship?

There wasn't one. NSLAB's ranged from 3/ml (and TBC 2,000/ml) to
180/ml (TBC of 20,000/ml). Then one TBC of 1,200,000/ml had NSLAB's of
100/ml.

>>Conclusions were:
>>2. The pH of one day old cheese showed a significant difference with
>>raw milk heat treatment. THe pH decreased with increasing milk heat
>>treatment. This was because the lower milk heat treatment left more
>>non-starter bacteria in the cheese to compete with the starter
>>bacteria for lactose and so less lactic acid was produced.
>
>So you presumably added a lactic starter culture. At some point the milk
>would have been warmed over 6C for further processing. When was the
>starter culture added in relationship to the warming?
>I am amazed that even at 1000 k/ml non-lactic bacteria could have
>significantly reduced the lactose levels unless the milk had been held
>at well over 6C for an extended period or stored for a more extended
>period (days).

Milk was fresh ie milked that morning and chilled on farm to 7oC. In
conventional NZ Blue cheese manufacture (ie without adjustment in heat
treatment) the milk is pre-heated in a plate heat exchanger to 60oC
and then separated. Cream to give the desired casein to fat ratio of
0.70 is the homogenised at 2750 psi before being blended back into the
skim milk. This standardised milk is return to the heat exchanger for
the pasteurisation step (72oC for 15 s) before being regeneratively
cooled against the incoming raw milk to 32oC and pumped into the
cheese vat.
Once each vat is filled, start culture is added: 0.5% Lactococcus
cremoris, and 0.08% Lactococcus diacetylactis. The vats are primed for
20 minutes before renneting.

>>6. The cheese appearence was superior in cheese made from milk heat
>>treated to 60oC or above. The cheese had a quite yellow tinge in milk
>>with lesser heat treatment. The yellow comes form the presence of
>>beta-carotene, always higher in NZ's pasture fed cow's milk that in
>>the grain fed cow's milk of Europe and America.
>
>I am intrigued. Why should this modest heat treatment affect the colour?
>
>>The milk with a lower
>>heat treatment went into the homogeniser at too low a temperature to
>>achieve proper homogenisation, giving free fat in the cheesemilk (and
>>cheese).
>
>This is a process related function. If the homogeniser requires milk at
>a particular temperature, shouldn't it have been raised to the
>appropriate temperature (preferably with starters added then or shortly
>afterwards).

Because we were working in a commercial factory environment, lowering
the heat treatment of the milk necessarily lowered the temperature of
the cream through the homogeniser. While the yellow colour was not
desirable, it was not a significant attribute compared to things such
as flavour and body.

>>7. The lower the heat treatment, the better the cheese sliced and the
>>smoother it was. Casein denaturation would definately be a factor in
>>this.
>
>Is this good or bad? To me it sounds good.

Definately good.

>>8. Cheese made from milk heat treated at 45oC and 60oC developed
>>off-flavours as it matured. This was due to the higher levels of
>>non-starter bacteria.
>
>a) I suppose one person's off flavours are another person's 'exquisite'
>flavours.

Debatable, but I can assure you our panel felt the flavours were "off"
and certainly not desirable or maketable.

>b) How often did this occur and how was it related to the TBC of the
>incoming milk?

All cheese made from milk heat treated at 60oC or less developed
off-flavours. Some of this cheese was indeed made from milk with TBC
>1,000,000/ml, but as explained above, the majority of the cheese was
made from TBC <30,000/ml and also developed off-flavours.


Email to john.abel@xtra.co.nz (home)  jsa@alpine.co.nz (work)

From: Oz <Oz@upthorpe.demon.co.uk>
Newsgroups: sci.bio.food-science,alt.cheese,alt.food
Subject: Re: Raw Milk Cheese - Opinions Anyone?!?
Date: Sat, 29 Nov 1997 07:18:17 +0000

In article <347dde9e.3117452@wingate>, Dale Anderson
<danders3@waun.tdsnet.com> writes
>Oz <Oz@upthorpe.demon.co.uk> wrote:
>
>
>>NB Still no comment on bactoscans of 30 k/ml vs mineral water .....
>
> I thought Ralph did a pretty good job on that, pointing out that it's
>not the total amount, but the amounts of *pathogenic* bacteria that
>counts.

1) So I am right, the TBC's for mineral water is 50 k/ml?

2) So the mineral water and soft juice manufacturers identify all those
bugs on a regular, weekly, basis? I very much doubt this from the visits
round plants shown on TV.

> I would add that the IFST statement states pretty clearly as to the
>problem, and gives substantial evidence that it is a problem.

Was a problem for lower quality milk, is perhaps more appropriate. It's
a bit pointless for the UK dairy industry to go overboard on ultra-high
quality hygeine milk if nobody takes any notice and still thinks it's as
contaminated as it was 10 or 20 years ago. The very considerable
increase in hygeine and (probably even more applicable) the weeding out
of the really unhygeinic producers (who probably had contamination
levels thousands of times higher than I am talking about) has produced a
huge reduction. The idea, twenty years ago, that milk could have fewer
bacteria than is allowed in mineral water would have been laughable. Now
it's here, nobody wants to know.

It's quite interesting that dairy farmers are being told to improve
their milk bacteriological because the buyers/public want it, yet in
fact from postings here it's quite clear that they are wonderfully
uninterested. Why bother? The cost of producing milk at these quality
levels is far from insignificant and if there is no benefit to the end
user (because everything is sterilised anyway) why are we bothering?
This is particularly so in that dairies pay no premium (although the
seeling group does) for higher quality.

> In order for bactoscans to be relevant to the issue of raw milk
>cheese making, one would first have to show that below a certain level
>raw milk cheese in a particular variety is as safe as the same variety
>using pasteurized milk.

A recent poster showed just this in his thesis.

>Given that, it would then need to be shown
>that any milk that comes above that given figure is either routed
>through a "kill step" like a pasteurizer, or is otherwise not allowed
>into the food chain. Since you said producers are only tested once a
>month,

Each producer is tested 52 times a year. Average of once a week.

>it's obvious this isn't going to happen on a producer level.

No, it should of course happen at the dairy. I understand that
bactoscans are very rapid and give results in about an hour. For the
larger dairy installing a bactoscan would perhaps be a smart move
anyway.


--
Oz

From: Oz <Oz@upthorpe.demon.co.uk>
Newsgroups: sci.bio.food-science,alt.cheese,alt.food
Subject: Re: Raw Milk Cheese - Opinions Anyone (long)
Date: Sat, 29 Nov 1997 17:43:36 +0000

In article <347f937c.5484780@news.xtra.co.nz>, Big John
<john.abel@xtra.co.nz> writes
>Oz <Oz@upthorpe.demon.co.uk> wrote:
>>
>>What test was used?
>Standard Methods Agar incuated at 30oC for 72 hours.

Ah, the 'old' method that used to be used in the UK. This was
discontinued because it missed many groups of bacteria (also because it
took 72 hrs, I suspect). The MMB suggested when we changed over that the
bactoscan gave results about six times higher. This is about right as we
went from a 6 month average of about 5 to about 25.

>>I find it hard to see how you had an AVERAGE TBC of 30k/ml if on some
>>days it was 1000 k/ml. This would require a lot of days at 10 k/ml. Are
>>you sure that the average was not 300 k/ml and the range 30-1000 k/ml,
>>which looks more plausible.
>We had 1 day at 1,200,000/ml . All other days were below 30,000/ml.

One day at 1200 k/ml is equivalent to 40 days at 30 k/ml. This means
that if the other days averaged 20 k/ml you must have done your work
over a period of 120 days. About right?

>(As an aside: this work was done in 1983. Standards of on farm hygiene
>have improved markedly since then. The 480 farms supplying my current
>company consistently average TBC of <5,000 /ml)

Indeed so.

>>I am most interested in the relationship between TBC and the levels of
>>NSLABS, particularly as these are quite possibly pathogens (mastitic) or
>>coliforms. Could you tell us this relationship?
>
>There wasn't one. NSLAB's ranged from 3/ml (and TBC 2,000/ml) to
>180/ml (TBC of 20,000/ml). Then one TBC of 1,200,000/ml had NSLAB's of
>100/ml.

So the levels of NSLABS are a very small fraction of the bacteria in
milk. I find this interesting as I was led to believe that at low TBC's
most of the bacteria were lactobacillae. Clearly this was incorrect.


>Milk was fresh ie milked that morning and chilled on farm to 7oC. In
>conventional NZ Blue cheese manufacture (ie without adjustment in heat
>treatment) the milk is pre-heated in a plate heat exchanger to 60oC
>and then separated. Cream to give the desired casein to fat ratio of
>0.70 is the homogenised at 2750 psi before being blended back into the
>skim milk.

So the temperature of this step is typically quite high, say about 50C
and so would not encourage the growth of bugs. For the unheated milk I
guess this stage would encourage growth.

>This standardised milk is return to the heat exchanger for
>the pasteurisation step (72oC for 15 s) before being regeneratively
>cooled against the incoming raw milk to 32oC and pumped into the
>cheese vat.

Filling time is?

>Once each vat is filled, start culture is added: 0.5% Lactococcus
>cremoris, and 0.08% Lactococcus diacetylactis.

I guess there is a reason why they are not introduced at the start of
filling.

>The vats are primed for
>20 minutes before renneting.

I guess this is another name for fermented.

>>>8. Cheese made from milk heat treated at 45oC and 60oC developed
>>>off-flavours as it matured. This was due to the higher levels of
>>>non-starter bacteria.
>>
>>a) I suppose one person's off flavours are another person's 'exquisite'
>>flavours.
>
>Debatable, but I can assure you our panel felt the flavours were "off"
>and certainly not desirable or maketable.

Blind or double blind testing?

>>b) How often did this occur and how was it related to the TBC of the
>>incoming milk?
>
>All cheese made from milk heat treated at 60oC or less developed
>off-flavours. Some of this cheese was indeed made from milk with TBC
>>1,000,000/ml, but as explained above, the majority of the cheese was
>made from TBC <30,000/ml and also developed off-flavours.

So there was no difference whether the milk had a TBC of 30 or 1200 k/ml
if pasteurised?

I also am pleased to see that you were utterly unconcerned about the
somatic cell count.

This is a very interesting bunch of info you are giving.

--
Oz

From: Oz <Oz@upthorpe.demon.co.uk>
Newsgroups: sci.bio.food-science,alt.cheese,alt.food
Subject: Re: Raw Milk Cheese - Opinions Anyone?!?
Date: Sat, 29 Nov 1997 20:36:17 +0000

Long reply, apologies:

In article <34805bba.51791239@wingate>, Dale Anderson
<danders3@waun.tdsnet.com> writes
>Oz <Oz@upthorpe.demon.co.uk> wrote:
>
>>In article <347dde9e.3117452@wingate>, Dale Anderson
>><danders3@waun.tdsnet.com> writes
>>>Oz <Oz@upthorpe.demon.co.uk> wrote:
>>>
>>>
>>>>NB Still no comment on bactoscans of 30 k/ml vs mineral water .....
>>>
>>> I thought Ralph did a pretty good job on that, pointing out that it's
>>>not the total amount, but the amounts of *pathogenic* bacteria that
>>>counts.
>>
>>1) So I am right, the TBC's for mineral water is 50 k/ml?
>
> Nary a clue, here. We don't concern ourselves from this angle in
>Wisconsin. Our concern is towards ingredient water, which is checked
>for E-coli monthly, the tolerence level of which is *zero*.

Hmmm. Checked *monthly*? I thought you (see below) said daily would
barely be adequate. Incidentally mineral water is not 'ingredient water'
and in the EU, at least, is not sterilised (cos it's 'natural'). I guess
you have EU mineral water, and even real ale, in the US?

You must live in a very sterile world where even the air does not
contain *any* bacteria. In short the tolerance is not 'zero', it's zero
for whatever test you are using, which is not the same thing at all.
Indeed depending on the test it could be very far from zero.

> Again, it's not the total amount, but the amount of pathogenic
>bacteria. If it could be guaranteed that milk from the farm would be
>zero for E-coli, Salmonella and Listeria, I'm sure there wouldn't be
>anywhere near as much of a concern in using raw milk for soft cheeses.

Even when cheeses made from known containated milk had zero count after
60 days? This passes your own specification. This does not gel with your
logic above. One rule for Coca-Cola but another for farmhouse cheese.
Now, why would that be, I wonder?

> From what I gleaned from the IFST statement, this is not totally
>possible. If one could develop a HACCP program that would guarantee
>that milk going into raw milk cheese was free of the three pathogens
>in question, I see no reason why it wouldn't be acceptable.

Perhaps it's more important to guarantee that the *cheese* is free. This
would also catch any failures in the batch for other reasons.

>>2) So the mineral water and soft juice manufacturers identify all those
>>bugs on a regular, weekly, basis? I very much doubt this from the visits
>>round plants shown on TV.
>
> In the case of the one bottler I had, they were testing the end
>product on a batch basis. If one is going to develop a workable HACCP
>program, that is the minimum one should do. Can't speak to what they
>do in your part of the world. I've found in most all industries the
>quality control is far above what we as a regulator are asking for.
>But then, over here there's always a fear of lawsuit, which can hurt
>more and longer than when we as a regulatory agency come down on them.
>;-)

Hmm, lawsuits. Someone must always be 'at fault'. I have to say that the
UK (soon to be superceded by some EC reg) test of 'reasonableness' was,
well, more reasonable. Before you jump in I have two very close
relatives who died as a result of someone's 'reasonableness' (nothing to
do with food), but at the end of the day no-one can really be expected
to do more than what is reasonable, nor can one expect them to see into
the future. I regard the US system of treasurehunting by suing some poor
innocent who was following regulations as best he or she could as
iniquitous and unjust. Grossly injust in fact.

>>Was a problem for lower quality milk, is perhaps more appropriate. It's
>>a bit pointless for the UK dairy industry to go overboard on ultra-high
>>quality hygeine milk if nobody takes any notice and still thinks it's as
>>contaminated as it was 10 or 20 years ago.
>
> The IFST statement points to examples in '94 and '95 of contaminated
>cheese.

Processed by pasteurisation, I believe. I also had a private post
(regrettably not posted here) that said that the case he was involved in
was caused by an infected wound from one of the workers in the factory.
We don't actually know if these cases were due to the milk, or not.

>That's only a couple years ago, when it comes down to it. It
>also points out that Listeria and Salmonella are being found at the
>bulk tank level on many farms. Pretty dangerous bit of Russian
>Roulette to me.

After 25 years of drinking raw milk, you will forgive me for not
bothering too much about this.

> While it can be pointed to as a milestone of sorts, in reality it's
>comparing apples and oranges. Unless on your side of the pond it's
>allowable to use as ingredient water for bottling water that is
>contaminated with levels of E-coli, Listeria, or Salmonella. We just
>wouldn't go with that over here....

As the moderator of PROMED said to me, it's not the presence of a bug
that produces disease, it's the *dose*. I would be delighted to know I
am ingesting sub-clinical doses of these bugs, it presumably maintains a
high level of immunity for me. Considering the pathogens that are about,
this is a good survival strategy. In other words a positive benefit in
this bacterially infected world we live in. I often wonder if fewer
people would be ill if they could be a bit more natural, and ingest a
low level of bugs on a regular basis.

>>The cost of producing milk at these quality
>>levels is far from insignificant and if there is no benefit to the end
>>user (because everything is sterilised anyway) why are we bothering?
>
> As a matter of fact, this debate is going on in the US right now,
>with those who are arguing a reduction in the standards is in order,
>since there is a kill step in the process. A true statement, when it
>comes to HACCP, but I'd give two reasons to not back up:
>
>1: Pasteurization is not sterilization. While it is not extreemly
>effective, it is not 100%.

Glory me, will a few escape? Tragic. Perhaps we should specify a
sensible maximum, say the average found on the hands of 1000 normal
people. No, on second thoughts that may be a few orders of magnitude too
high. Maybe the same level as in the mouth saliva of 1000 normal people,
no, I guess that would be too high too. Perhaps we should all live in
rooms and areas as sterile as an operating theater? No, silly me, that
would *definitely* be too high. Why do we need our food sterile anyway?
OK lets eat out of cans. That's sterile until opened.  :-)

I wonder if Americans are sometimes a bit too paranoid?

>2: I don't think the dairy industry wants to put in the minds of the
>consumer that it doesn't strive for 100% quality, particularly in the
>area of cleanliness, and particularly in the case of something like
>milk. Maybe it's not as tight for producers over there, but a cut in
>consumption over here is going to result in farmers going out of
>business.

Costs too high, prices too low. Production too high.
What you need is quotas ....

> *Any* milk. Once a week isn't going to cut it, if the protection is
>going to be provided. Every pickup would have to be tested,

It is for antibiotics, it could be for bacteria.

>and there
>would have to be a method of diverting high milk before it goes into a
>raw product.

You pasteurise that batch, of course.

>Otherwise, you take the chance of sending some milk from
>one producer above a certain level into a comingled tank, thereby
>contaminating the whole tank. Just watering down pathogens doesn't
>sound like a good policy from my angle. With some of these pathogens,
>I think zero tolerance is a must.

There is no such thing as zero tolerance. You can't have it. Anywhere.

> I would tend to think what would be needed would be levels of zero
>tolerance on E-coli, Listeria, and Salmonella, myself. If you don't
>have that, you really don't have the safety level you have from milk
>coming out of a pasteurizer.

Natural things have bugs on them. I guess you wash your veg in chlorine
in case some bird has cr*pped on it. Personally, I think this is going
over the top. Zero is a stupid (and I use it advisedly) tolerance. It
should be safe, ie sensibly below the level *shown* (not 'deduced') to
cause natural infection in normal people.

> There's one thing I find interesting, and that's that there's
>arguement to not worry about pathogenic bacteria levels in food on
>your side of the pond, while there are arguements to ban rBGH over
>there. To be honest, I see pathogens as far more of a threat...

I'm not that sure that I am altogether typical of a UK denizen.
Personally, looking at the **science**, I don't think rBGH, 'hormones'
(properly used) or a natural level of bugs is of the slightest risk to
any normal person.

Incidentally, that latest issue of New Scientist has a nice article on
work that has shown a negative correlation between asthma and infection
with childhood diseases (vaccination doesn't protect here). Slowly we
are seeing that trying to live a life in a 'sterile' manner is not only
un-natural, but may bring on other diseases.

--
Oz

From: Oz <Oz@upthorpe.demon.co.uk>
Newsgroups: sci.bio.food-science
Subject: Re: Raw Milk Cheese. Opinions Anyone?!?
Date: Sat, 29 Nov 1997 23:01:44 +0000

In article <3485147b.25089145@news.easynet.co.uk>, J Ralph Blanchfield
<jralphb@easynet.co.uk> writes

>In place of Oz, who usually asks this sort of question, I'll ask it
>for him "Which enzymes in milk kill which bacteria? References,
>please"

I didn't ask it since I assumed that a poster writing in a foreign
language and with perhaps a less than utterly fluent grasp of English
might well have substituted a word he knew for one he didn't. There are
antimicrobials in milk, but they aren't very good. The low pH in
yoghurts and some cheeses is better and most bugs produce antimicrobials
of some sort to poison any interlopers trying to get in on their act. I
suspect this is why fermented products are quite common and were
regarded as 'antiseptic', at least to some extent (eg wine), despite
being full of bugs.

>The fact is that microbiological surveys of raw milk reveal
>the presence of pathogens. The most recent surveys in the UK, by the
>Public Health Laboratory Service (PHLS) and ADAS, so alarmed the UK
>Advisory Committee on Microbiological Safety of Foods (ACMSF) that it
>called for the banning of the retail sale of raw milk in England,
>Wales and Northern Ireland (it has long been banned in Scotland).

Hmmm, you mean Scotland where they have all the EC0157 outbreaks?  :-)

>There may be something in acclimatisation, but if so it can afford
>only limited protection to only some people. Alf's hypothesis would
>require France and Switzerland, where raw milk cheese has always been
>very common, to be exempt from major food poisoning outbreaks from raw
>milk cheese. In fact, of the previously mentioned 13 major outbreaks
>associated with raw milk cheese, 2 were in France, 2 in  Switzerland,
>and one in both countries.

Hmmm. Out of 13 major outbreaks only 5 were in countries where raw milk
cheeses are very common.

One is surprised that 95% are not from countries where raw milk cheeses
are very common.

One is unlikely indeed to have a *major* outbreak in countries where
they are rare.

How many outbreaks were there from pasteurised cheeses over the same
period?

--
Oz

From: john.abel@xtra.co.nz (Big John)
Newsgroups: sci.bio.food-science,alt.cheese,alt.food
Subject: Re: Raw Milk Cheese - Opinions Anyone (long)
Date: Mon, 01 Dec 1997 08:23:42 GMT

Oz <Oz@upthorpe.demon.co.uk> wrote:

>>>What test was used?
>>Standard Methods Agar incuated at 30oC for 72 hours.
>
>Ah, the 'old' method that used to be used in the UK. This was
>discontinued because it missed many groups of bacteria (also because it
>took 72 hrs, I suspect). The MMB suggested when we changed over that the
>bactoscan gave results about six times higher. This is about right as we
>went from a 6 month average of about 5 to about 25.

That's interesting. I visited the MMB lab outside of Surbiton in 1991
and they were using the TBC count then - when did you change to
bactoscan?

Our company has changed to bactoscan this year, although bactoscans
have been in use in NZ for several years. Our experience (both within
our company and in other NZ organisations) has been the opposite of
what you describe. For a start we have found a generally good
correlation between TBC and bactoscan results after running the two
methods side by side for several months. If anything, the bactoscan
has tended to give a lower reading. Our discussions with
microbiologists in NZ and Foss Denmark (the manufacturer of the
bactoscan) have said that the bactoscan will not detect some of the
bacteria detected by TBC, specifically strep mastitis bacteria.

Although this has caused some farmers problems, there is no doubt that
the majority appreciate a result in a few minutes compared to three
days.

<snipped>

>Filling time is?

From memory, about 15 minutes.

>>Once each vat is filled, start culture is added: 0.5% Lactococcus
>>cremoris, and 0.08% Lactococcus diacetylactis.
>
>I guess there is a reason why they are not introduced at the start of
>filling.

Only that any variation in filling time can be overcome by waiting
until the vat was full before addding the starter bacteria and thus
keeping better control of the subsequent cheesemaking process.

>
>>The vats are primed for
>>20 minutes before renneting.
>
>I guess this is another name for fermented.

Yes. In other words the bacteria was given 20 minutes to work before
the rennet was added to the vat.

>>>a) I suppose one person's off flavours are another person's 'exquisite'
>>>flavours.
>>Debatable, but I can assure you our panel felt the flavours were "off"
>>and certainly not desirable or maketable.
>
>Blind or double blind testing?

I am not familiar with the terms. The cheese were presented in
groups, identifed only by a (random) number. The cheese graders did
not know what heat treatment the cheese milk had and evaluated each on
its merits.

>>All cheese made from milk heat treated at 60oC or less developed
>>off-flavours. Some of this cheese was indeed made from milk with TBC
>>>1,000,000/ml, but as explained above, the majority of the cheese was
>>made from TBC <30,000/ml and also developed off-flavours.
>
>So there was no difference whether the milk had a TBC of 30 or 1200 k/ml
>if pasteurised?

We couldn't say that as the raw milk for the pasteurised milk runs
were all below 30,000 /ml. As a cheesmaker, a high TBC would not
concern me if the milk was only a few hours old. However milk with
high TBC kept for longer can cause problems. Firstly enzymes produced
from the bacteria will survive pasteurisation and can cause
off-flavours in maturing cheese (particularly the higher pH varieties
such as Gouda or Colby). Secondly, poor quality milk can block up
separators and pasteurisers.

>I also am pleased to see that you were utterly unconcerned about the
>somatic cell count.

We certainly were unconcerned in the 1980's. In 1997 SCC is a big deal
for us. Partly because of the EU regulations, and also because high
SCC means poor animal health and reduces cheese yield.


Email to john.abel@xtra.co.nz (home)  jsa@alpine.co.nz (work)

From: Oz <Oz@upthorpe.demon.co.uk>
Newsgroups: sci.bio.food-science,alt.cheese,alt.food
Subject: Re: Raw Milk Cheese - Opinions Anyone (long)
Date: Tue, 2 Dec 1997 07:00:14 +0000

In article <34826838.858137@news.xtra.co.nz>, Big John
<john.abel@xtra.co.nz> writes
>
>That's interesting. I visited the MMB lab outside of Surbiton in 1991
>and they were using the TBC count then - when did you change to
>bactoscan?

Quite a few years ago, from memory.

>Our company has changed to bactoscan this year, although bactoscans
>have been in use in NZ for several years. Our experience (both within
>our company and in other NZ organisations) has been the opposite of
>what you describe. For a start we have found a generally good
>correlation between TBC and bactoscan results after running the two
>methods side by side for several months. If anything, the bactoscan
>has tended to give a lower reading. Our discussions with
>microbiologists in NZ and Foss Denmark (the manufacturer of the
>bactoscan) have said that the bactoscan will not detect some of the
>bacteria detected by TBC, specifically strep mastitis bacteria.

Odd, exactly the reverse of what was said here. Certainly there was a
jump from 0 to 5 k/ml under plating to 20-30 under bactoscan. The reason
was given that the bugs that grow on the plates depend on the medium and
growth conditions (temp etc) whilst the bactoscan picks up all the bugs
caught by the antibody (probably a mixture). In particular the plate
test did not detect the low temperature bugs cruicial for keeping
quality.

Having said that one ought to bear in mind that calibration and checking
of automated systems is often poor. The results from the UK grain trade
being particularly suspect. The fact that a machine costs $200,000 does
not guarantee that it will give the correct result and various
conversion parameters can be tweaked to match any result one might care
to follow.

What is sure is that somatic cell count has no interest to manufacturers
and should be abandoned as a hygeine requirement.

>>So there was no difference whether the milk had a TBC of 30 or 1200 k/ml
>>if pasteurised?
>We couldn't say that as the raw milk for the pasteurised milk runs
>were all below 30,000 /ml. As a cheesmaker, a high TBC would not
>concern me if the milk was only a few hours old. However milk with
>high TBC kept for longer can cause problems.

Agreed,

>Firstly enzymes produced
>from the bacteria will survive pasteurisation and can cause
>off-flavours in maturing cheese (particularly the higher pH varieties
>such as Gouda or Colby).

I wouldn't disagree.

>Secondly, poor quality milk can block up
>separators and pasteurisers.

That's not poor quality milk. That's farmhouse raw yoghurt you got
delivered instead of milk! Aaaaargh!

>We certianly were unconcerned in the 1980's. In 1997 SCC is a big deal
>for us. Partly because of the EU regulations, and also because high
>SCC means poor animal health and reduces cheese yield.

At last. AT LAST!

Someone who is concerned about SCC. The poor animal health is of
doubtful importance under 250k, particularly in old animals (who have
naturally higher SCC). I am at a loss to understand why the cheese yield
is reduced since I would have thought it was largely determined by the
protein content of the milk.

I hope we are not using results from the 70's and 80's on animals and
milk with SCC in the ++1M's and extrapolating this to the 200k's. This
is a typical EU habit since they never listen to their scientists and
don't understand science very well.

--
Oz

From: Oz <Oz@upthorpe.demon.co.uk>
Newsgroups: sci.bio.food-science
Subject: Re: Raw Milk Cheese - Opinions Anyone?!?
Date: Tue, 2 Dec 1997 07:22:46 +0000

In article <348aae12.45076929@news.easynet.co.uk>, J Ralph Blanchfield
<jralphb@easynet.co.uk> writes
>Hello Oz and Everyone,
>
>Wine is a different proposition depending
>partly on the preservative effect of alcohol and partly on the added
>preservative sulphur dioxide.

I was thinking of centuries past, Romans and Middle ages who used wine
for antiseptic properties. No SO2 in it then, I warrant.


>>Hmmm. Out of 13 major outbreaks only 5 were in countries where raw milk
>>cheeses are very common.
>
>Hmmm. But of the  8 outside France and Switzerland , 7 were raw milk
>cheeses and the eighth was a cheese made with pasteurised milk to
>which raw milk had been added (see below).
>
>>One is surprised that 95% are not from countries where raw milk cheeses
>>are very common.
>
>One is not the least bit surprised. On the contrary, if
>acclimatisation immunity to the extent that Alf postulated existed,
>there should be a negligible percentage.

This probably IS a negligeable %!

>The figures have been repeatedly stated, 13 out of 17 major
>outbreaks,associated with raw milk,  which by difference leaves 4 not
>shown to be associated with raw milk, which must therefore be assumed
>to be associated with infection from some other source during ripening
>and storage.

Ok, so about 3/4 of the oubreaks are from cheeses made from untreated
milk. So I have about 3x the risk, OK maybe more, of listeriosis if I
eat these cheeses. Now if it was 100x or more I might worry. I suspect
that quality control has been improved where they are made so reducing
the risk still further.

--
Oz

From: john.abel@xtra.co.nz (Big John)
Newsgroups: sci.bio.food-science,alt.cheese,alt.food
Subject: Re: Raw Milk Cheese - Opinions Anyone (long)
Date: Wed, 03 Dec 1997 06:55:03 GMT

Oz <Oz@upthorpe.demon.co.uk> wrote:

<snipped>
>>We certianly were unconcerned in the 1980's. In 1997 SCC is a big deal
>>for us. Partly because of the EU regulations, and also because high
>>SCC means poor animal health and reduces cheese yield.
>
>At last. AT LAST!
>
>Someone who is concerned about SCC. The poor animal health is of
>doubtful importance under 250k, particularly in old animals (who have
>naturally higher SCC). I am at a loss to understand why the cheese yield
>is reduced since I would have thought it was largely determined by the
>protein content of the milk.

As I understand it, there are two factors involved in reduced cheese
yield from high SCC animals.

Firstly, mastitis scars the udder tissue. This is irreversable, and
reduces the available milk producing tissue. Animals with consistenly
high SCC may produce 30% less milk than a healthy cow. Extrapolated
over a herd, or over a dairy company's milk supply base, I beleive
that low SCC will give more milk to be processed.

The second effect observed in higher SCC animals is that they produce
less casein protein. So while the overall level of protein produced by
the animal is not affected, the proportion of that protein that is
useable in cheesemaking is lower.

Again, the amount of casein drop is not great. But when you are making
300 tonnes of cheese a day (as we are at the moment) having a low SCC
supply base must be worth a few extra kilos of cheese 8-)


Email to john.abel@xtra.co.nz (home)  jsa@alpine.co.nz (work)

From: Oz <Oz@upthorpe.demon.co.uk>
Newsgroups: sci.bio.food-science,alt.cheese,alt.food
Subject: Re: Raw Milk Cheese - Opinions Anyone (long)
Date: Wed, 3 Dec 1997 12:03:20 +0000

In article <3484f870.429527@news.xtra.co.nz>, Big John
<john.abel@xtra.co.nz> writes
>>
>As I understand it, there are two factors involved in reduced cheese
>yield from high SCC animals.
>
>Firstly, mastitis scars the udder tissue. This is irreversable, and
>reduces the available milk producing tissue.

This is a problem for the farmer, and not the dairy.

>Animals with consistenly
>high SCC may produce 30% less milk than a healthy cow.

One thinks of beefburgers here.

>Extrapolated
>over a herd, or over a dairy company's milk supply base, I beleive
>that low SCC will give more milk to be processed.

Except that culling old, healthy, disease resistant cows because their
TBC has risen to 250 results in reduced efficiency and lower yields.
It's not very smart genetically either. This is a big *disadvantage* in
trading milk with specified low SCC.

>The second effect observed in higher SCC animals is that they produce
>less casein protein. So while the overall level of protein produced by
>the animal is not affected, the proportion of that protein that is
>useable in cheesemaking is lower.

How big is this effect. I am more interested in old healthy cows with
slightly elevated SCC (say averaging circa 250k) who are NOT mastitic.
Whilst there is a correlation between SCC and mastitis there is an even
bigger one with TBC's and mastitis.

>Again, the amount of casein drop is not great. But when you are making
>300 tonnes of cheese a day (as we are at the moment) having a low SCC
>supply base must be worth a few extra kilos of cheese 8-)

What proteins are being produced in lieu of casein? Do you have any idea
of the mechanism that causes this shift? Would it be very hard to
analyse casein by herd instead of protein so getting round this small
problem?

For those who are not familiar with dairy herds I ought to point out
that feeding can produce changes in milk protein content of between
typically 2.9% and 3.5% in the drymatter. I strongly suspect that this
is 10, or even 1000, times higher than any SCC effect. [Ie who cares].

--
Oz

From: john.abel@xtra.co.nz (Big John)
Newsgroups: sci.bio.food-science,alt.cheese,alt.food
Subject: Re: Raw Milk Cheese - Opinions Anyone (long)
Date: Sun, 07 Dec 1997 00:05:26 GMT

Oz <Oz@upthorpe.demon.co.uk> wrote:
<snipped>

>>The second effect observed in higher SCC animals is that they produce
>>less casein protein. So while the overall level of protein produced by
>>the animal is not affected, the proportion of that protein that is
>>useable in cheesemaking is lower.
>
>How big is this effect. I am more interested in old healthy cows with
>slightly elevated SCC (say averaging circa 250k) who are NOT mastitic.
>Whilst there is a correlation between SCC and mastitis there is an even
>bigger one with TBC's and mastitis.

Sorry Oz, you are getting way out of my area of expertise here (as a
chemical engineer involved in large-scale cheesemaking). Dale has made
a useful follow-up post here on the changes in protein structure. Are
there any animal health people who could help us out here?

>>Again, the amount of casein drop is not great. But when you are making
>>300 tonnes of cheese a day (as we are at the moment) having a low SCC
>>supply base must be worth a few extra kilos of cheese 8-)
>
>What proteins are being produced in lieu of casein? Do you have any idea
>of the mechanism that causes this shift? Would it be very hard to
>analyse casein by herd instead of protein so getting round this small
>problem?

Whey proteins are produced instead. I do not know the mechanism, but
scientists form NZ Dairy Research Institute that I have spoken to
about this effect gave me the impression that this was an established
fact.

The difficulty is in large scale measurement of casein. We use an
instrument called a Milkoscan (Foss, Denmark) which uses infra-red
asorbance to measure the amount of fat, protein, and lactose in the
milk. We test each of our farmers every pickup for payment purposes -
about 1500 samples each day. Our two milkoscans each test about 250
samples per hour. There are no instruments available that can measure
casein protein at that sort of throughput.

Whey proteins themselves are not a _bad_ thing - we make a whey
protein concentrate powder from them, but they are of no us in
cheesemaking.


>For those who are not familiar with dairy herds I ought to point out
>that feeding can produce changes in milk protein content of between
>typically 2.9% and 3.5% in the drymatter. I strongly suspect that this
>is 10, or even 1000, times higher than any SCC effect. [Ie who cares].

Probably (I'm guessing here), in NZ the pasture feeding of our herds
does not lead to the same fluctuations in protein production.

 As a low SCC herd is easily achievable (based on how fast the SCC in
our supplying herds dropped once we started penalising farmers), why
not lower the SCC and give us cheesemakers a hand?


Email to john.abel@xtra.co.nz (home)  jsa@alpine.co.nz (work)