In this study, the antihypertensive activity in spontaneously hypertensive rats of two peptides isolated from β-lactoglobulin hydrolysates with thermolysin was evaluated. These peptides, with sequences LLF [β-lg f(103–105)] and LQKW [β-lg f(58–61)], showed potent in vitro ACE-inhibitory activity. Two hours after administration, both sequences caused a clear and significant decrease in the blood pressure of these rats. The impact of a simulated gastrointestinal digestion on ACE-inhibitory and antihypertensive activities of these peptides was also studied. The results showed that both fragments were susceptible to proteolytic degradation after incubation with pepsin and Corolase PP®. In addition, their in vitro ACE-inhibitory activity decreased after the simulated digestion. It is likely that fragment LQK was the active end product of the gastrointestinal digestion of peptide LQKW. The fragment LL, observed after digestion of peptide LLF, probably exert its antihypertensive effect through a mechanism of action different than ACE-inhibition.

Capillary electrophoresis using a hydrophilically coated capillary and a low pH buffer containing urea has been used to characterize processed cheeses. Different electrophoretic patterns were obtained depending on the ingredients used in the blend such as acid casein, rennet casein, sodium and calcium caseinates and skim milk powder. Isoelectric casein, and sodium and calcium caseinates were shown to contain intact non-glycosylated κ-casein (κ-CN), while rennet casein contained only trace amounts of κ-CN and mainly para-κ-CN. Therefore, the addition of casein or caseinate to processed cheeses has been detected by analysing the intact non- glycosylated κ-CN. Quantitation of intact non-glycosylated κ-CN in processed cheeses of known and unknown composition was carried out using a regression curve from standard mixtures of 150–550 g isoelectric casein/kg total rennet casein. This capillary electrophoresis method successfully confirmed the addition of isoelectric casein or caseinate to processed cheeses of known composition. The quantitative determination range was 0·605–3·688 mg κ-CN/ml. This method cannot be used for measuring additions of rennet casein or any caseinates that have been exposed to chymosin.

Polymorphism of caprine milk proteins was studied by capillary electrophoresis. Identification of casein (CN) fractions was effected by using isolated fractions from cation-exchange fast protein liquid chromatography. Genetic polymorphisms in caprine αs2-CN, αs1-CN, β-CN and κ-CN have been determined. κ-CN A and B, β-CN A and null, αs2-CN A, B and C, αs1-CN A, B, C and null, and other forms with intermediate and low αs1-CN content have been identified. The capillary electrophoresis method made it possible to analyse whole caprine milk using simple sample preparation and was rapid, automated and suitable for phenotyping studies. This method may also permit the quantitative study of different protein fractions.

Polymorphism of ovine αs1-caseins was studied by capillary electrophoresis at pH 3·0±0·1. Individual caseins (CN) were selected according to their genetic variants, as determined by PAGE and isoelectric focusing. The ovine caseins, containing different genetic variants of αs1-CN and αs2-CN, were fractionated by cation-exchange FPLC®. The αs1-CN variants A, B and C, and the fast moving αs2-CN variant were identified by a capillary electrophoresis method. The fast moving αs2-CN variant, so-called for its behaviour in PAGE, also had a faster electrophoretic mobility than the common αs2-CN when analysed by the present technique. The capillary electrophoresis method gave excellent, rapid, automated separation of αs1-CN and αs2-CN variants and was suitable for screening studies.

Capillary electrophoresis using a hydrophilically coated capillary and a low pH buffer containing urea has been used to follow the proteolytic action of plasmin and chymosin on isolated casein fractions, whole casein and individual milk samples selected on the basis of their genetic variants. Several of the main casein breakdown products were identified. These included, among others, γ1-casein (CN) A1, γ1-CN A2, γ1-CN B, γ1-CN C, γ2-CN A, γ1-CN A3, γ2-CN B, γ3-CN A and γ3-CN B, as well as proteose peptones, arising from the action of plasmin on the different genetic variants of β-CN. αs1-I-CN and αs1-CN f(1-23) from αs1-CN, and para-κ-CN and caseinomacropeptide from κ-CN produced by chymosin action were also separated. The knowledge of their migration times provided information on the extent and origin of casein hydrolysis in both milk and cheese, as found in samples of proteolysed milk or fresh cheese.

Volatile components of four batches of Manchego cheese were studied throughout their ripening process. Samples were submitted to a micro simultaneous distillation-extraction procedure, and then analysed by capillary gas chromatography (GC) and combined GC and mass spectrometry. Among other components, four homologous series of compounds were found: free fatty acids, methyl ketones, ethyl and methyl esters of even fatty acids. Ripening stage can be approximately estimated from the concentrations of some components.