Bioactive peptides (BPs) derived from animal and plant proteins are important food functional ingredients with many promising health-promoting properties. In the food industry, enzymatic hydrolysis is the most common technique employed for the liberation of BPs from proteins in which conventional heat treatment is used as pre-treatment to enhance hydrolytic action. In recent years, application of non-thermal food processing technologies such as ultrasound (US), high-pressure processing (HPP), and pulsed electric field (PEF) as pre-treatment methods has gained considerable research attention owing to the enhancement in yield and bioactivity of resulting peptides. This review provides an overview of bioactivities of peptides obtained from animal and plant proteins and an insight into the impact of US, HPP, and PEF as non-thermal treatment prior to enzymolysis on the generation of food-derived BPs and resulting bioactivities. US, HPP, and PEF were reported to improve antioxidant, angiotensin-converting enzyme (ACE)-inhibitory, antimicrobial, and antidiabetic properties of the food-derived BPs. The primary modes of action are due to conformational changes of food proteins caused by US, HPP, and PEF, improving the susceptibility of proteins to protease cleavage and subsequent proteolysis. However, the use of other non-thermal techniques such as cold plasma, radiofrequency electric field, dense phase carbon dioxide, and oscillating magnetic fields has not been examined in the generation of BPs from food proteins.

The growing demand for plant-based protein alternatives has driven interest in protein modifications to enhance their functional properties in food applications. Enzymatic cross-linking using laccases derived from Rhus vernicifera (LR) and transglutaminase (TG) offers a promising strategy to enhance protein solubility, emulsifying properties, and foaming properties of food proteins. This study varied the enzymatic reaction conditions, including enzyme concentration, pH, temperature, incubation time, and ferulic acid addition, for the most effective cross-linking between proteins in lupin flour (LF) and soy protein isolate (SPI), resulting in changes in physicochemical and functional properties of the cross-linked proteins. LR-induced cross-linking in lupin and soy proteins was most favourable at 142.5 U/100 mg protein, pH 6, and 20 °C, where ferulic acid enhanced cross-linking efficiency with prolonged incubation (20 h). TG-induced cross-linking in lupin and soy proteins was most favourable at 1.25 U/100 mg protein, pH 6 and 30 °C, where high-molecular-weight aggregates were observed. Cross-linking modified protein surface characteristics, increasing ζ-potential and particle size due to protein aggregation, while ferulic acid further enhanced polymerisation. Morphological analysis revealed a porous powder structure across all samples with increased porosity in cross-linked samples as evidenced by the predominance of small fragments within the particles. Prolonged incubation led to partial disaggregation in LR-treated samples unless they were stabilised by ferulic acid. Under mild conditions (1 h, pH 6, 20 °C), LR and ferulic acid-added samples showed minor and significant improvements in protein solubility and foaming stability, respectively. Additionally, a significant increase in foaming ability was observed in ferulic acid-added LR samples after prolonged incubation (20 h), compared to the corresponding control. In contrast, prolonged incubation (20 h) or TG treatment had a lower foaming stability compared to the mild LR treatment. Emulsifying ability and emulsion stability showed limited variation across treatments. These findings suggest that cross-linking conditions influence specific functional properties, highlighting the need for further optimisation to achieve desired protein functionality in food applications.

The market for plant-based drinks (PBDs) is experiencing a surge in consumer demand, especially in Western societies. PBDs are a highly processed food product, and little is known about this relatively new food product category when compared to bovine milk. In the present study, the storage stability, proteolysis and generation of free amino acids were investigated in commercially available PBDs over the course of a one-year storage period. Generally, pH, color and protein solubility were found to be stable in the PBDs during storage, except for the pea-based product, which showed less protein solubility after storage. The pea-based drinks also had higher initial levels of free N-terminals prior to storage compared with levels for the other plant-based drinks, as well as significantly increasing levels of total free, and especially bitter free, amino acids. The development of free amino acids in the oat-based drink indicated that the released amino acids could be involved in various reactions such as the Maillard reaction during the storage period.

Apricot kernels are known for being a rich source of oil, protein, and bioactive compounds. This study focused on enhancing the bioactivities of apricot kernels through fermentation. Additionally, this study explored the correlations between polyphenols, amino acids, antioxidant activities, and total phenolic content (TPC). The findings indicated that apricot kernels fermented with Lactiplantibacillus plantarum exhibited increased antioxidant activity, as assessed by the FRAP and CUPRAC methods, and an increased TPC compared to naturally fermented samples. The CUPRAC activity increased significantly from 1.03 to 1.82 mg of ascorbic acid per gram of sample on day 7, and the FRAP activity increased from 4.9 to 12.2 mg of ascorbic acid per gram of sample on day 3 of fermentation. Moreover, the TPC significantly increased from 1.67 to 7.58 mg of gallic acid per gram of sample on day 9 of fermentation. The results further demonstrated that, during the fermentation process, the concentration of hydroxybenzoic acid increased from 0.52 µg/g on day 0 to 5.3 µg/g on day 9. The DL-3-phenyllactic acid content demonstrated a significant increase from 0.42 µg/g on day 0 to 99.62 µg/g on day 5, while the benzoic acid content exhibited a notable increase from 45.33 µg/g to 138.13 µg/g over the fermentation period, with peak levels being observed on day 5. Similarly, most amino acids demonstrated a rise in concentration as the fermentation progressed, peaking on the ninth day. This study further employed random forest regression as a form of explainable artificial intelligence (XAI) to explore the relationships between phenolic compounds, amino acids, and antioxidant activities. Amino acids like L-cystine and L-anserine were found to positively impact FRAP values, while L-histidine and 1-methyl-L-histidine contributed to the CUPRAC antioxidant activity. Notably, hydroxybenzoic acid emerged as a key contributor to both the FRAP value and TPC, highlighting its significance in improving the overall antioxidant capacity of apricot kernels. These findings indicate that, under optimised fermentation conditions, apricot kernels hold promise as functional food ingredients due to the beneficial antioxidant properties observed in this study.

Plant-based protein is considered a sustainable protein source and has increased in demand recently. However, products containing plant-based proteins require further modification to achieve the desired functionalities akin to those present in animal protein products. This study aimed to investigate the effects of enzymes as cross-linking reagents on the physicochemical and functional properties of hybrid plant- and animal-based proteins in which lupin and whey proteins were chosen as representatives, respectively. They were hybridised through enzymatic cross-linking using two laccases (laccase R, derived from Rhus vernicifera and laccase T, derived from Trametes versicolor) and transglutaminase (TG). The cross-linking experiments were conducted by mixing aqueous solutions of lupin flour and whey protein concentrate powder in a ratio of 1:1 of protein content under the conditions of pH 7, 40 °C for 20 h and in the presence of laccase T, laccase R, or TG. The cross-linked mixtures were freeze-dried, and the powders obtained were assessed for their cross-linking pattern, colour, charge distribution (ζ-potential), particle size, thermal stability, morphology, solubility, foaming and emulsifying properties, and total amino acid content. The findings showed that cross-linking with laccase R significantly improved the protein solubility, emulsion stability and foaming ability of the mixture, whereas these functionalities were lower in the TG-treated mixture due to extensive cross-linking. Furthermore, the mixture treated with laccase T turned brownish in colour and showed a decrease in total amino acid content which could be due to the enzyme’s oxidative cross-linking mechanism. Also, the occurrence of cross-linking in the lupin and whey mixture was indicated by changes in other investigated parameters such as particle size, ζ-potential, etc., as compared to the control samples. The obtained results suggested that enzymatic cross-linking, depending on the type of enzyme used, could impact the physicochemical and functional properties of hybrid plant- and animal-based proteins, potentially influencing their applications in food.