Proteolysis of Cheese Slurry Made from Pulsed Electric Field-Treated Milk

Abstract

Raw milk cheeses have unique flavor and texture characteristics not obtainable in cheeses made from pasteurized milk. However, cheeses made from pasteurized milk are widespread, primarily for public health reasons. Pulsed electric field (PEF) treatment as a non-thermal pasteurization method has shown its ability to keep the flavor and natural characteristics of food samples intact, thus providing advantage over conventional heat processing. In this study, PEF treatment was performed in a continuous treatment chamber, consisting of two parallel stainless steel electrodes separated by a 50-mm-thick insulator. A 30-kV pulse generator was used to deliver bipolar square waveform electric field to milk sample. Pulse width was 2 µs; pulse frequency was 2 Hz, and up to 120 pulses were applied. Cheese curds were made from raw milk, pasteurized milk, and PEF-treated milk, and their proteolysis processes were compared using curd slurry incubated at 30°C for 5 days. The profiles of water-soluble peptides were measured using an reversed-phase highperformance liquid chromatography (RP-HPLC) system. The concentration of free amino acids was measured by Cd-ninhydrin method. Results indicated that PEF-treated milk has intermediate proteolysis profiles between raw milk and pasteurized milk in terms of peptide and free amino acid concentration. The results showed the potential of making high-quality cheeses by PEF treatment without sacrificing the natural characteristics of the cheeses.

Angiotensin converting enzyme‐inhibitory activity and antimicrobial effect of fermented camel milk (Camelus dromedarius)

“…The free amino acid content of WSE from fermented and unfermented camel milk was determined and expressed as absorbance at 507 nm on a UV–Vis spectrophotometer using Cd‐ninhydrin method, as described by Yu et al . ().…”

“…The Ortho-phthaldialdehyde method was used to determine the degree of hydrolysis of WSE from fermented and unfermented camel milk at an absorbance of 340 nm using a UV-Vis spectrophotometer, and expressed as free amino group (FAG) concentration (mM) of Leu-Gly as described by Church et al (1983). The free amino acid content of WSE from fermented and unfermented camel milk was determined and expressed as absorbance at 507 nm on a UV-Vis spectrophotometer using Cd-ninhydrin method, as described by Yu et al (2012).…”

Short communication: A new minicurd model system for hard cooked cheeses

“…In recent years, several attempts have been made to find an ideal cheese model, but the quality of a model is always related to the objectives of each investigation. In general, the composition of model acid curds and slurries differs greatly from that of a real cheese (Farkye et al, 1995;Choi et al, 2006;Yu et al, 2012). Choi et al (2006) obtained curds with 90% moisture and 3% proteins; Farkye et al (1995) obtained slurries of Cheddar cheeses with 57% moisture and 23% proteins; and the model proposed by Milesi et al (2008) contained ~61% moisture and 18% proteins.…”

Effect of proteolysis during Cheddar cheese aging on the detection of milk protein residues by ELISA

“…Several extraction and fractionation protocols, based on the liberation of peptide fragments and free AA, have been developed to evaluate the extent of ripening and proteolysis in cheese (Møller et al, 2012;Yu et al, 2012;Karametsi et al, 2014). As aging continues, the number of large peptides isolated from cheese dramatically decreases, and ripening is dominated by the release of small peptides and free AA (Parente et al, 2012;Møller et al, 2013).…”