Stability and cytotoxicity of angiotensin-I-converting enzyme inhibitory peptides derived from bovine casein

Abstract

This study investigated the effect of heat treatment combined with acid and alkali on the angiotensin-Iconverting enzyme (ACE) inhibitory activity of peptides derived from bovine casein. The free amino group content, color, and cytotoxicity of the peptides were measured under different conditions. When heated at 100 °C in the pH range from 9.0 to 12.0, ACE inhibitory activity was reduced and the appearance of the peptides was significantly darkened. After thermal treatment in the presence of acid and alkali, the free amino group content of ACE inhibitory peptides decreased markedly. High temperature and prolonged heating also resulted in the loss of ACE inhibitory activity, the loss of free amino groups, and the darker coloration of bovine casein-derived peptides. However, ACE inhibitory peptides, within a concentration range of from 0.01 to 0.2 mg/ml, showed no cytotoxicity to Caco-2 and ECV-304 cell lines after heat treatment. This indicated that high temperature and alkaline heat treatment impaired the stability of bovine casein-derived ACE inhibitory peptides.

Effects of heat and pH treatments and in vitro digestion on the biological activity of protein hydrolysates of Amaranthus hypochondriacus L. grain

“…Thus, bioactivity may diminish or be lost (Bloom et al 2015). In agreement with research by Wu et al (2014), this work suggested that hydrolysates with ACEIA could be stable in the heat and time treatments of food processes carried out in temperatures ranging from 60 to 100°C and also for short periods of time. In a study by Hwang (2010) peptides derived from tuna cooking juice proteins retained ACEIA.…”

“…Peptide fractions of hydrolysates (80 g/l) were separately adjusted to pH 4.0 and 7.0 with buffer solution and heated (40, 60, 80, 100 and 120°C) for 1 h. The pH effect on bioactivity of hydrolysates was assessed using various buffer solutions at different pH values (1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, and 12.0), which were heated at 100°C for 1 h. To investigate the effect of the duration of heat treatment, peptide solutions were adjusted to pH 4.0 or 7.0 and incubated at 100°C for 1.0, 2.0, 3.0, or 4.0 h. Unheated peptide fractions were used as control (Wu et al 2014). …”

“…Temperature and time may be crucial factors that may lead to loss of bioactivity. Wu et al (2014) found that the ACEIA of bovine casein-derived peptides showed no significant change after heating at different temperatures (40-100°C) at pH 7.0 after 2 h of treatment, while heat treatment for 3.0 h or 4.0 h slightly decreased ACEIA (p \ 0.05). Those authors claimed that the relationship between peptide structure-bioactivity, was unclear.…”

“…This may be ascribed to the fact that a heat treatment at those extreme pH ranges can damage some amino acids of the inhibitory peptides. Denaturation and even hydrolysis of some peptides can also affect the inhibitory activity triggered by the pH (Wu et al 2014). pH modification can also prompt physico-chemical changes of proteins such as denaturation, intermolecular reactions, reaction with sugars, solubility and, thus, cause crosslinking, lysine damage, non specific cleavage of peptides and damaged amino acids prone to pH changes.…”

Impact of Power Ultrasound on Antihypertensive Activity, Functional Properties, and Thermal Stability of Rapeseed Protein Hydrolysates

“…However, when the hydrolysates were heated above 100 ∘ C, the ACE inhibition rate significantly decreased. When compared to that of the control group, the ACE inhibitory activity decreased by 20.50% at 120 ∘ C. Extreme heating or sterilization may result in the decrease of ACE inhibitory activity due to loss of some available peptides [66,67]. Furthermore, the C-terminal residues strongly influence the ACE inhibition and it is also enlarged by the presence of the +ve charge lysine and arginine as C-terminal residue.…”