A2 Milk

[darius]

Okay, just gotta ask if anyone knows if A2 milk is better for making cheese than A1 milk (which dominates the US market)?

If you are unfamiliar with the A1-A2 milk controversy, I wrote a bit about on my blog about a year ago, or you could do a Google (or whatever) search.
http://2footalligator.blogspot.com/2010/03/black-or-brown-cow-milk-controversy.html

I'm pretty adamant about good milk if I can get it, which is almost never unless I buy a cow. As I'm a bit long in the tooth, that's not too likely!

[linuxboy]

What do you mean by "better"? Or are you looking for a discussion of casein function as it related to curd strength, casein-casein interaction, etc?

[darius]

Hmmmm, not sure exactly what I mean, LOL.

I suppose I basically wonder if anyone has actually noticed any difference in any cheese made from one vs the other. (There's not much of a way to measure "nutritionally healthier" on the average dining table, although that does concern me.)

I'm not savvy enough (yet, and maybe never) to grasp casein function as it relates to curd strength, or casein-casein interaction.

[linuxboy]

Gel strength is determined more by k-casein subtype, which in turn partly determines micelle size (cow breeds can have micelles that are almost as small as sheep and almost as big as goat... lot of variation). So in terms of the cheesemake, the breed and milk composition makes a difference, but not directly due to b-casein or casomorphine, more due to k-casein.

There have not been enough studies done (zero that I know of) to isolate effects of b-casein composition in terms of genetic differences on flavor formation during aging. Most of the work has been about bitter peptide formation from b-casein hydrolysis. For a good overview of the A1/A2 studies, please see Kaminski et al study: http://www.guernsey.net/~wgcf/PageMill_Resources/2007_Volume_48_3-189-198.pdf

[darius]

Interesting paper, Thanks.

[ArnaudForestier]

There have not been enough studies done (zero that I know of) to isolate effects of b-casein composition in terms of genetic differences on flavor formation during aging.

Pav, the article I cited in the other thread does seem to go into this, at least in part; most of it is on the rheological properties with genetic variants, but it does attempt some evaluation of sensory aspects, in both K- and B- casein variants.   

The beneficial effect of variant B of κ and β-caseins on the rheological properties of clotted milk and on cheese yield has been evidenced in numerous studies [35, 54, 72].
Variant B reduces clotting and curd-firming times and leads to firmer rennet curd than variant A. Those properties are reflected by the higher cheese-making suitability of milk containing variant B, along with better fat matter retention in the casein network, hence better cheese yield with the same level of useful material (proteins and fat) of processed milk. On the other hand, the
effect of those variants on the sensory characteristics of ripened cheeses is still open to question. Comparing the three most frequent haplotypes of αs1, β and κ-caseins (BBB, BA2A and CA2B) in the Normande breed [54] led to clarifying the cheesemaking value ascribed to variant B of these caseins.

...

The Tarentaise cattle breed, included in  the PDO Beaufort specifications, differs from other dairy breeds in its higher frequency
of rare variants of αs2, β and κ- caseins. The cheese-making consequences
of this particularity have been explored.

This study revealed the originality of variant C of β-casein, whose frequency was as high as 17% in the Tarentaise breed, whereas it was nearly non-existent in most other dairy breeds in France [54]. Initial studies were conducted on individual β- casein C (β-Cn C) or β-casein A (β-Cn (a frequent variant in most breeds) cows' milk samples according to a miniature, cooked, pressed cheese-making technology derived from that of Beaufort cheese. Milk
behaviour in cheese vats, proteolysis, structure, texture and flavour of β-Cn C cheeses were compared with those of β-Cn A cheeses.

It appeared that β-Cn C cheeses, which contained less fat and whose structure
was irregular (as observed by electronic microscopy), were characterised by
a firmer and less elastic structure than β-Cn A cheeses. β-Cn C cheeses tasted different and were more piquant than β-Cn A cheeses [32, 75]. To validate these results, Beaufort cheeses were made by the same cheesemaker at the same time in two different vats in a Northern Alps cooperative, in the spring over two consecutive years, either with milk containing high (80%) or low (15%)
proportions of variant C of β-casein (Tab. II).

The sensory analysis of ripened cheeses by a panel of judges elicited no major differences in cheese textures. In contrast, cheeses made with β-Cn C milk were saltier, and despatched a stronger, more animal and more lemony flavour. Their smell was also rated as more intense, more diversified and milkier.

Another trained panel for sensory analyses working in parallel also found that β-Cn C cheeses exhibited more intense smell and flavour and used the descriptor "pungent" more often to describe the smell of β-Cn C
cheeses [76].

Need to read this, several times, but interested nonetheless. 

[linuxboy]

Those are "sensory evaluations". Meaning someone somewhere tried a cheese and deemed it to be different. Science, but not good science. I meant research using identical makes and mini-wheels, accounting for slight milk variations, and then doing protein and flavor analysis. Haven't seen anything like that. Sorry, I don't trust sensory panels. There is a way they can be authoritative, but that requires a 300-page discussion of flavor descriptions and their loose correlation to underlying chemical properties.

Interesting to read nonetheless. I like that study more for its discussion of k-casein properties and genetic work.

[ArnaudForestier]

Totally agree with you, Pav, on the weight of sensory panels.  Markers like "salty taste," "intense," "milky" or "animal" aroma or odor are pretty weak.  Much like in my former world, political economy, "thermometer" polls on just about anything - useless, really.  I just found it interesting that there was even some attempt to link genetic variants with sensory impressions.  I also found the discussions of rheological properties interesting (it's all new to me); e.g.,

The beneficial effect of variant B of κ and β-caseins on the rheological properties of clotted milk and on cheese yield has been evidenced in numerous studies [35, 54, 72].

Variant B reduces clotting and curd-firming times and leads to firmer rennet curd than variant A. Those properties are reflected by the higher cheese-making suitability of milk containing variant B, along with better fat matter retention in the casein network, hence better cheese yield with the same level of useful material (proteins and fat) of processed milk. On the other hand, the
effect of those variants on the sensory characteristics of ripened cheeses is still open to question.

(emphasis mine...the crux of the hole, it seems to me).