F. M. V. Coppen

273. The consistency of cheese curd at the pitching point and its bearing on the firmness and quality of the finished cheese

1. The pitching consistency of some 470 cheese has been determined at one factory and the data compared with the subjective judgements of a skilled cheesemaker. The smallest difference in consistency which the expert can distinguish with a reasonable degree of accuracy (threshold) is compared with those for purely elastic and viscous bodies, and it is concluded that the consistency at pitching is judged mainly from the elastic properties of the curd. The good agreement between these thresholds substantiates the hypothesis that our test for pitching consistency is closely related to the requirements of the practical cheesemaker. 2. The connexion believed to exist between firmness of curd at pitching and acidity was not substantiated, in the case of Cheddar, by a statistical examination of the available data. 3. The most usual values (medians) for pitching consistency are compared for four different factories, and it is shown that differences in technique may be associated with the same pitching consistency and produce very similar cheese, but that in other cases good cheese may be produced from very different pitching consistencies. The important thing is that the pitching consistency should be known and controlled so as to be as constant as possible under given conditions. 4. A technique is described for measuring the force required to thrust a skewer into cheese. This force ( S ) is highly correlated with “body” judged subjectively by an experimenter who was aware of the fact that such a correlation was to be tried. Judgements of “body” made by expert cheese graders were not so correlated, but the interpretation of their judgements was inadequate, so that no definite conclusion can be drawn.

282. A preliminary study of the effects of varying pitching consistency and rate of scald on the physical and chemical properties of Cheddar cheese and on the firmness of the cheese as judged by cheese-makers, bakers and others

1. Six cheese of Cheddar type were made under conditions as similar as possible, except that the consistency of the curd at pitching, and in two cases the rate of scald, were varied. 2. Chemical and rheological analyses, as well as measurements of moisture content and vapour pressure, were made on the cheese and also judgements of firmness under various conditions were given by cheese-makers, bakers and non-experts. 3. A table is given in which the orders of placing of the cheese are compared as between the objective tests and the subjective judgements. The cheese-makers and the non-expert testers gave, in general, characteristically different orders, the orders given by the bakers tending to fall between the two. 4. It appears that the consistency of the curd at the pitching point ( W/h as determined by the Scott Blair-Coppen method) and probably the rate of scald, are prime factors in determining the firmness of the cheese. 5. The whole experiment is preliminary in character and it is intended to repeat it in an extended form in the near future.