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Three Zygomycetes, Mortierella isabellina, Thamnidium elegans and Mucor sp., were tested for their ability of producing biomass and lipid‐containing γ‐linolenic acid (GLA) during their cultivation on cheese whey. M. isabellina consumed all of the available lactose and a significant amount of the available protein. On the contrary, the two other fungi seemed incapable of consuming lactose after protein exhaustion. In the second series of experiments, for M. isabellina a supplementary quantity of lactose was added into the medium in order to increase the C/N ratio and hence to increase the production of fat. In the case of T. elegans and Mucor sp., a supplementary quantity of ammonium sulfate was added in order to favor the consumption of lactose and the production of biomass. Indeed, enhancement of lipid production was observed for M. isabellina and biomass production for T. elegans and Mucor sp.. Fatty acid analysis of the microbial lipid showed a composition that presented non‐negligible changes in relation with the age of the culture and the C/N molar ratio of the medium. Further analysis of the fat showed that the quantity of neutral lipids was the more abundant. The fatty acid composition of neutral lipids resembled to that of total lipids. Phospholipids were the more unsaturated fraction for Mucor sp. and M. isabellina. GLA was synthesized in all trials but its concentration presented differences related with the utilized strains and the fermentation time. Growth of M. isabellina on lactose‐supplemented whey resulted in a maximum GLA production of 301 mg/L.

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-Four cheesemaking trials were conducted in three different traditional Feta cheese plants. The characteristics of the cheesemaking process had to do with: the heat treatment of the cheese milk, the use of yoghourt as a starter, the use of traditional rennet from kids' and lambs' abomasa, and the packaging in wooden barrels without brine addition. At 60 d (minimum ripening period according to Greek Codex Alimentarius), the percentage of water soluble nitrogen (WSN) varied from 15.88% to 19.58% of total nitrogen (TN) and 73.4%-79.9% of the WSN was nitrogen soluble in 12% TCA. At the same age, 13.3-23.6% of WSN was nitrogen soluble in 5% PTA. The quantitative and qualitative changes of the middle area of the RP-HPLC profiles (A 220 ) indicated the evolution of nitrogenous fractions during the ripening and the effect of each cheese plant technology on them. Most of the qualitative and quantitative changes occured during the pre-ripening period (18 d). In general, the rate of proteolysis was similar to that of the industrially made Feta. However, the percentages of low molecular weight fractions were higher. Feta cheese / proteolysisRésumé -Évolution de la protéolyse au cours de l'affinage de fromage Feta fabriqué par les fromageries traditionnelles. Quatre fabrications expérimentales de fromage Feta ont été réalisées dans trois différentes fromageries traditionnelles. La technologie adoptée par ces fromageries se caracté-rise par : une pasteurisation en cuve, l'utilisation de yaourt comme levain, l'emprésurage par la pré-sure traditionnelle obtenue à partir de caillettes d'agneaux ou de chevreaux ainsi que l'emballage et le stockage dans des barils en bois sans ajout de saumure complémentaire. de l'affinage ainsi que l'effet de la technologie des différentes fromageries. La plus grande partie des changements qualitatifs et quantitatifs a été observée pendant les 18 premiers jours d'affinage. La vitesse de la protéolyse a été égale à celle de fromage Feta fabriqué industriellement. Cependant les valeurs des fractions azotées de faible poids moléculaire étaient plus élevées.Feta / fromage / protéolyse