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The strong and characteristic “goat” flavour is one of the most important quality components of French cheeses made from goat milk. This study was designed in order to evaluate the impact of different ripening strains on this typical flavour. Goat milk was incubated with selected ripening strains (yeasts and moulds), and two types of cheeses were produced: Sainte-Maure cheese (lactic coagulation technology) and Camembert-type cheese (lactic-rennet coagulation technology). Sensory evaluation of the cheeses was performed by trained panellists, and physico-chemical parameters (including lipolysis) were measured. The results showed that cheeses made with Geotrichum candidum as a ripening agent were characterised by a strong typical flavour, whereas the use of Penicillium candidum was detrimental for the sensorial quality of cheeses. These results were related to the lipolytic and flavouring activities of the different strains, which displayed considerable quantitative and qualitative variations.

An in vitro study was conducted to investigate the sensitivity of lactose-β-lactoglobulin conjugates to β-galactosidase from Kluyveromyces lactis. The hydrolysis was monitored by ion exchange chromatography. Compared to free lactose or lactulose, which were rapidly hydrolysed, protein-bound lactose was not hydrolysed by β-galactosidase even after an extended hydrolysis time. Tryptic digestion of the conjugates before addition of β-galactosidase improved the substrate accessibility and led to the release of about 50% of the linked lactose. The results strongly suggest that the resistance of protein bound lactose is linked to the globular and compact structure of lactose-β-lactoglobulin conjugates.

Direct monitoring of the Amadori product formation between lactose and β-lactoglobulin was performed by electrospray ionisation mass spectrometry. As expected, the glycation reaction was faster at low water activity than in aqueous system. Heterogeneous β-lactoglobulin glycoforms were observed, with different number of lactose bound: populations of β-lactoglobulin with 1 to 7 and 2 to 11 linked lactose were detected, respectively, after 10 and 22 h of reaction under 65% relative humidity and 50°C. Trypsinolysis of glycated proteins, followed by reverse-phase HPLC coupled to tandem mass spectrometry in the neutral loss scanning mode, indicated that all potential reactive amino groups, except Lys101, were involved in sugar binding. The resulting order of reactivity, as a function of reaction time, was as follows: Lys47,91>α-amino-group, Lys15,70,100>Lys60,69,75,77,83,135,138>Lys8,141.

Lactose reacts nonenzymatically with beta-lactoglobulin (beta-LG), the major whey protein, under mild heat treatment and the formation of the complex may be monitored by mass spectrometry. Using Reverse Phase HPLC coupled with Electrospray Ionization MS (ESI-MS) we have measured the global extent of glycosylation and examined the distribution of lactose among the beta-LG glycoforms. Identification of lactosylated sites by trypsinolysis and Tandem MS indicate that, although the glycosylation reaction was non-specific and potentially involved all the reactive sites (alpha- and epsilon-amino groups), beta-LG appeared to have at least two populations of lysine with the distinct ability to react with lactose. These results underline the structural heterogeneity of beta-LG glycoforms, with respect to the number of lactose linked per molecule and to the binding sites involved, which could affect the biological function of beta-LG.