Whey protein isolate polydispersity affects enzymatic hydrolysis outcomes

Abstract

The effects of heat-induced denaturation of whey protein isolate (WPI) on the enzymatic breakdown of α-La, caseinomacropeptide (CMP), β-Lg A and β-Lg B were observed as hydrolysis proceeded to a 5 % degree of hydrolysis (DH) in both unheated and heat-treated (80 ºC, 10 min) WPI dispersions (100 g L -1 ). Hydrolysis of denatured WPI favoured the generation of higher levels of free essential amino acids; lysine, phenylalanine and arginine compared to the unheated substrate. LC-MS/MS identified 23 distinct peptides which were identified in the denatured WPI hydrolysate -the majority of which were derived from β-Lg. The mapping of the detected regions in α-La, β-Lg, and CMP enabled specific cleavage points to be associated with certain serine endo-protease activities. The outcomes of the study emphasise how a combined approach of substrate heat pre-treatment and enzymology may be used to influence proteolysis with attendant opportunities for targeting unique peptide production and amino acid release.

Influence of denaturation and aggregation of β-lactoglobulin on its tryptic hydrolysis and the release of functional peptides

“…Denaturation of WPI was done at 80°C for 10 min and the number of peptides released by hydrolysis of included proteins was investigated. However, regarding b-LG as individual protein, the amount of released peptides was reduced to 85% at DH 5% (O'Loughlin et al, 2013). That also the duration of heat-treatment and the thereby achieved degree of denaturation, influences the hydrolysis of b-LG was shown by Stanciuc et al (2008).…”

“…Whereas the hydrolysis kinetics and the time dependent release of peptides during tryptic hydrolysis of native b-LG are well described by Cheison, Schmitt, Leeb, Letzel, and Kulozik (2010) and Fernández and Riera (2013), detailed information on the hydrolysis of denatured b-LG and the impact of denaturation on the release of peptides is missing. To date, thermally induced denaturation of the substrate prior to its hydrolysis was investigated for whey protein isolate (WPI) and whey protein concentrate (WPC) by Adjonu et al (2013), O'Loughlin, Murray, Kelly, FitzGerald, andBrodkorb (2012), O'Loughlin et al (2013), Stanciuc, Hintoiu, Stanciu, and Rapeanu (2010), Zhang and Vardhanabhuti (2014). In addition, reports on heat denaturation of pure b-LG as substrate for subsequent hydrolysis have been published Peram, Loveday, Ye, & Singh, 2013;Stanciuc, van der Plancken, Rotaru, & Hendrickx, 2008).…”

“…However, O'Loughlin et al (2012) determined the amount of residual native protein and took into account that the initial substrate was a mixture of both, native and denatured proteins. A more detailed investigation by O'Loughlin et al (2013) showed that although the thermal pre-treatment of WPI solutions enhanced the digestibility of the protein mixture, cleavage sites for enzymatic attack within the b-LG fraction of the heat-treated WPI were reduced. These results agreed with the work of Stanciuc et al (2008) who reported a decrease in digestibility of b-LG with prolonged heating of the protein solution prior to its hydrolysis.…”

X-ray diffraction analysis of lactose crystallization in freeze-dried lactose–whey protein systems

“…α-lactose monohydrate (Sigma-Aldrich, St. Louis, Mo., U.S.) and whey protein isolate (WPI; Isolac®, Carbery Food Ingredients, Co., Ballineen, Ireland; impurities including carbohydrates or lipids b3%) were used (O'Loughlin et al, 2013). Lactose was dissolved in distilled water to obtain 20% (w/w) solution and then cooled to room temperature (20 ± 3°C).…”

A casein hydrolysate protects mice against high fat diet induced hyperglycemia by attenuating NLRP3 inflammasome‐mediated inflammation and improving insulin signaling

“…The drinking water was changed and monitored three times per week during the 12‐wk study period. The hydrolysate fraction was characterized by MS as described previously and consists of the sequence YPVEPFTESQSLTLTDVENLHLPLPLLQSWMHQPHQPLPPTVMFPPQSVLSLSQSK or shorter fragments derived from this sequence as outlined in the patent according to international publication number WO/2015/173266 .…”