Stelios Kaminarides

Cheese whey as a renewable substrate for microbial lipid and biomass production by Zygomycetes

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.

Effect of draining temperature on the biochemical characteristics of Feta cheese

Two different draining temperatures, 15 and 21°C were applied to five Feta cheese curds made with different starters, containing mesophilic or thermophilic strains or mixtures of them. After 20 h of draining, the pH of curds made with thermophilic starters ranged from 5.28 to 5.49. The draining temperature significantly affected (P<0.05) the pH and the total solids of the cheeses. The inclusion of whey proteins in the cheese curd due to the insufficient draining of cheeses at 15°C, resulted in higher water-soluble nitrogen (WSN), as % of total nitrogen content. Free amino acid contents were significantly affected (P<0.05) by the draining temperature and by the presence of thermophilic lactobacilli in the starter mixture. Draining temperature also significantly affected (P<0.05) residual αs- and β-casein and the RP-HPLC profiles of the WSN. The C2:0 to C8:0 free fatty acids, hardness (kg) and fracturability (kg), as well as the total organoleptic scores, were significantly (P<0.05) higher in feta drained at 21°C.

Detection of bovine milk in ovine yoghurt by electrophoresis of para-κ-casein

The possibility of detection and determination of bovine milk in adulterated yoghurt by cationic polyacrylamide gel electrophoresis (PAGE) of yoghurt caseins, treated with rennet, was examined. Yoghurts made from bovine and ovine milk and from known mixtures of the two were examined. The evaluation of bovine milk in yoghurt was based on the optical density of the bovine para-κ-casein band, which was distinctly separated and bore a linear relationship to the percentage of bovine milk in the mixtures. By using PAGE of bovine para-κ-casein, levels of bovine milk as low as 1% were easily detected in ovine yoghurt.

Volatile compounds and lipolysis levels of Kopanisti, a traditional Greek raw milk cheese

BACKGROUND Kopanisti is a Protected Designation of Origin (PDO) traditional soft Greek cheese manufactured exclusively in the Cycladic island complex. It is made from raw bovine, ovine or caprine milk or a mixture of them without the addition of any lactic acid cultures. It has a spreadable texture, an intense salty and peppery taste and a strong flavour. Although Kopanisti cheese has properties similar to those of mould-ripened cheeses, its volatile compound content has never been reported. In this study the volatile compound content and lipolysis level of ten commercial Kopanisti samples were investigated. RESULTS The main aromatic groups found in Kopanisti cheese were alcohols, esters and volatile free fatty acids. Ethanol and several ethyl esters were the main volatile compounds. Intense lipolysis was present, with an average total free fatty acid content of 48,979 mg kg(-1). Acetic, butyric and capric acids were the main volatile acids determined. CONCLUSION The intense lipolysis contributes greatly to the strong flavour and peppery taste of Kopanisti cheese. The flavour of Kopanisti is attributable mainly to the volatile fatty acids and various other volatile compounds as well as to the interactions occurring between them.

Ripening changes in Kopanisti cheese.

Changes in a Greek traditional soft cheese, Kopanisti, were followed during ripening. The a s -casein content was hydrolysed faster than the β-casein so that in mature cheese only 23% and 35% respectively of these proteins remained intact. Leucine, γ-aminobutyric acid, valine and alanine were the dominant free amino acids in the mature cheese. Lipolysis was intense. The characteristic rich flavour and peppery taste appeared after 16 d ripening and the best overall cheese quality was produced after 32 d maturation

The effect of addition of skimmed milk on the characteristics of Myzithra cheeses.

Myzithra cheese is a traditional Greek whey cheese. Three types of Myzithra cheese were produced from A: 100% whey; B: 90% whey+10% ovine milk and C: 90% whey+10% skimmed ovine milk and were evaluated. The addition of skimmed milk to whey resulted in a new dietary product, containing 9.24% fat, with good quality, a harder texture and higher levels of ash, Ca, Mg and K than those of experimental cheeses A and B. Electrophoretic patterns and HPLC chromatograms of the proteins of Myzithra cheeses revealed the presence or not of αs-CN to the whey cheeses. In addition, SDS-electrophoresis of proteins under special preparation of samples permitted for first time the separation of whey-cheese protein (WP) components that had been denatured during cooking of the whey.