M. Alcalá

Proteolysis of Cabrales cheese and other European blue vein cheese varieties

The extent and level of proteolysis were evaluated in Cabrales and five other European blue vein cheese varieties, Bleu de Bresse, Danablu, Edelpilzkase, Gorgonzola and Roquefort, by analysing their different N-containing constituents and determining the degree of casein hydrolysis. The electrophoretic patterns of the caseins in the cheeses confirmed their strong proteolysis, components featuring the lowest electrophoretic mobility offering the greatest resistance to subsequent hydrolysis. Component α s1 — I was detected in all varieties studied with the exception of Roquefort cheese.

Measurement and calculation of water activity in Blue cheese

Wateractivity ( a w ), pH, and several chemical components were determined in 20 samples of Blue cheese belonging to the varieties Bleu de Bresse, Cabrales, Danablu, Edelpilzkase, Gorgonzola and Roquefort. The a w in these cheeses could be calculated from chemical data on a water content basis (g/100 g H 2 O) by two simple equations: where SN is the soluble nitrogen. Differences between calculated and measured a w using these relationships were similar to those obtained with a more complex equation described by Ruegg & Blanc (1983).

Improved equation for cryoscopic estimation of water activity in cheese

Abstract Cryoscopes employed in dairy plants for routine quality control of milk can be used for the determination of the water activity (Aw of cheese according to the equation: A w =1·0155+0·1068. fp where fp is the freezing point in °C of an aqueous extract of cheese solutes obtained under standard conditions. This linear regression equation was obtained for 139 pairs of Aw and fp measurements. The differences between the measured and calculated Aw values in the range 1·00–0·90 were only greater than 0·02 Aw units in a small number (6·5%) of the samples with the lower Aw values. Hence this cryoscopic approach can be applied by the cheese industry as a straightforward quality control technique.

Calculation of water activity in surface mould-ripened soft cheeses from their chemical composition

Abstract The water activity (Aw) of 24 samples of 12 different brands of Brie cheese and another 12 of Camembert cheese was measured at 20°C by four methods (psychrometric, cryoscopic, dew-point hygrometric and isopiestic equilibration). The cheeses were also analysed chemically for their moisture, salt (NaCl), ash and non-protein nitrogen (NPN) contents. A linear regression analysis of data pairs of the variables [NaCl], [Ash] or [NPN] (in g/100 g moisture) and Aw (average values of the four methods) yielded the following relations A w =0·9813−0·0045 [NaCl] A w =0·9769−0·0019 [Ash] A w =0·9793−0·0101 [NPN] On the other hand, a multiple linear regression analysis of sets of g ash/100 g moisture, g NPN/100 g moisture and average Aw at 20°C led to the equation A w =0·996−0·0029 [Ash] − 0·0106 [NPN] All four equations can be used alone or in conjunction to predict the water activity of surface mould-ripened soft cheeses. The differences between the calculated and measured (average) Aw values were similar to those yielded by the four measurement methods used.

Determination of water activity in Brie and Camembert cheese varieties by four different methods.

Abstract The water activity (A w ) of single samples from 12 brands of Brie cheese and 12 brands of Camembert cheese was measured at 20°C by using four methods based on different principles, namely psychrometry, cryoscopy, dew-point hygrometry and isopiestic equilibration. The average A w values found (± standard deviation) for the Brie and Camembert cheese were 0·965 ± 0·005 and 0·967 ± 0·009, respectively. The mean difference between methods was less than 0·005 A w units, while the mean deviation from the average A w values was ± 0·005 A w units. The mean deviations from the average A w for the entire population of samples of the two cheese varieties were 0·000, +0·001, +0·001 and −0·003 A w units for the gravimetric (isopiestic), psychrometric, cryoscopic and hygrometric methods, respectively. The average pH values measured (± standard deviation) were 6·96 ± 0·44 and 7·01 ± 0·47 for the Brie and Camembert cheese, respectively.

Comparison of methods for determination of high water activities. Application to dairy products and juices.

Water activity was determined in various dairy products (ice creams, yoghourts and flavoured milks) and several juices by three different methods: psychrometric, cryoscopic and gravimetric. The differences between the AW values provided by the three methods were also calculated. Such differences were always smaller than 0·005 Aw units, which allows the use of a straightforward method (gravimetric) together with two instrumental methods (psychrometric and cryoscopic) for the determination of high Aw values (in the range 0·999–0·900) in the aforesaid types of products.