COMPOSITION, YIELD, TEXTURE AND AROMA COMPOUNDS OF GOAT CHEESES AS RELATED TO THE A-VARIANT AND O-VARIANT OF ALPHA(S1) CASEIN IN MILK

Sainte-Maure soft cheeses were prepared from two goat milks with extre me composition regarding alpha(sl) casein (CN), one having a high alph a(sl) CN level (A variant), the other having no alpha(sl) CN in its ca sein (O variant). A and O cheeses from four successive experiments wer e analyzed after 2 and 13 days of ripening and compared for their char acteristics. A milk had a higher total nitrogen matter level, compared to O milk (30.9 versus 23.3 g kg(-1)), due to the presence of alpha(s l) CN (4.7 versus 0.0 g kg(-1)) and had also a higher fat level (28.5 versus 25.1 g kg(-1)). The resulting A and O cheeses had the same gros s composition at day 2: total solids (TS) = 37.9% (standard deviation 0.1%) and fat/TS = 45.8%. Cheese yields at day 2 were higher by 26% in A cheeses than in O cheeses (15.15 versus 12.00 kg cheese/100 kg milk ). The fatty acid distribution in the total fatty acids of A and O che eses reflected the specific differences already described between A an d O milks. Free fatty acid level at day 13 amounted to 3.5% and 3.9% r espectively for A and O cheeses. In the free fatty acid fraction at da y 13, the distribution of fatty acids was the same as in the TFA of th e respective A and O cheeses, meaning that no specificity occurred in the hydrolytic activity of the main working lipase, the Penicillium ca ndidum lipase of the surface flora. The texture of the A and O cheeses was different, A cheeses being firmer as determined by organoleptic t ests as well as by two types of rheological measurements (Young modulu s determination and characterization by penetrometry). Determinations were made on cheeses at day 2 and day 13 and the results showed that t he differences at day 13, while already significant, were lowered by t he ripening process. The typical goat aroma was significantly lower in A cheese than in O cheese as shown by the results of the organoleptic tests at day 2 (P = 0.05) and at day 13 (P = 0.01). This was confirme d by the chemical determination (gas chromatography/mass spectrometry) of the goaty volatile aroma compound levels in the cheeses at day 13: these compounds, hexanoic, octanoic, nonanoic, decanoic, 4-methylocta noic and 4-ethyloctanoic, were lower by 50% in A cheese compared to O cheese. (C) Inra/Elsevier, Paris.