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Angiotensin-I-Converting Enzyme (ACE) inhibitors peptides were produced from unsupplemented acid goat whey fermented aerobically for 168 h byKluyveromyces marxianusandLactobacillus rhamnosus. This yeast-lactobacillus association is GRAS. Two novel lactokinins were identified: NYW and W with IC50of 20 and 0·86 μmrespectively. They both were resistant toward simulated gastrointestinal digestion. In addition, WLAHK was found in the hydrolysate. These three sequences belong tof(99–110) of α-la which seems to be a lactokinin cryptic zone. W was the major molecule released by the fermentation process. Considering that W is the precursor of serotonin, the hydrolysate produced could be of interest for the generation of functional health ingredient involved in regulation of affective disorders and hypertension.

The influence of pH (4·5–6·5), sodium chloride content (125–375 mM), calcium chloride content (10–30 mM), protein concentration (70–90 g/l) and lactose content on the gel hardness of goat whey protein concentrate (GWPC) in relation to the origin of the acid whey (raw or pasteurized milk) was studied using a factorial design. Gels were obtained after heat treatment (90 °C, 30 min). Gel hardness was measured using texture analyser. Only protein concentration and pH were found to have a statistically significant effect on the gel hardness. An increase in the protein concentration resulted in an increase in the gel hardness. GWPC containing 800 g/kg protein formed gels with a hardness maximum at the pHi, whereas GWPC containing 300 g/kg protein did not form true gels. Whey from pasteurized milk formed softer gels than whey from raw milk. A high lactose content (≈360 g/kg) also reduced the gelation performance of GWPC.

This paper presents a novel contribution to the purification of goat β-lactoglobulin by using an ultrafiltration membrane enzymic reactor. The basis of the purification process was the enzymic hydrolysis of contaminating proteins, α-lactalbumin and traces of serum albumin, by pepsin at 40 °C and pH 2, conditions under which β-lactoglobulin is resistant to peptic digestion. Simultaneously, β-lactoglobulin and peptides were separated by ultrafiltration. β-Lactoglobulin was retained in the reactor while peptides generated by hydrolysis from α-lactalbumin and serum albumin permeated through the membrane. The process was made continuous by the addition of fresh whey to replace the lost permeate. Three mineral membranes with 10, 30 and 50 kDa molecular mass cut-off were tested and the 30 kDa membrane was selected for the continuous process. The simultaneous purification and concentration of β-lactoglobulin from clarified goats' whey was achieved in a single step. The ultrafiltration membrane enzymic reactor could treat eight reactor volumes of clarified whey. The recovery of β-lactoglobulin was 74%, its purity was 84% and its concentration 6·6-fold that in the initial clarified whey.

Goat whey was hydrolysed by pepsin in an ultrafiltration membrane enzymic reactor coupled with a 30 kDa mineral membrane. Peptides collected in the permeate were resolved using reversed-phase HPLC. Their sequences were determined by amino acid analysis, second order derivative spectra analysis and mass spectrometry. Owing to the resistance of β-lactoglobulin (β-lg) towards pepsin, the majority of peptides identified were derived from α-lactalbumin (α-la). Pepsin showed a broad specificity of hydrolysis sites and generated a wide range of products from dipeptides to very large peptides containing disulphide bridges. The molecular masses of peptides resulting from α-la degradation were between 150 and 6900 Da: 36% were < 600 Da, 24% were 600–2000 Da and 40% were > 2000 Da.