Subin R. C. K. Rajendran

Encapsulation of food protein hydrolysates and peptides: a review

Food protein hydrolysates and peptides are considered a category of promising functional food ingredients. However, commercial application of protein hydrolysates and their constituent peptides can be impeded by their low bioavailability, bitter taste, hygroscopicity and likelihood of interacting with the food matrix. Encapsulation as a delivery mechanism can be used to overcome these challenges for improving the bioavailability and organoleptic properties of the peptides. Proteins, polysaccharides and lipids are the three carrier systems that have been utilized in food peptide encapsulation. The protein and polysaccharide systems mainly aim at masking the bitter taste and reducing the hygroscopicity of protein hydrolysates, whereas the lipid-based systems are intended for use in enhancing the bioavailability and biostability of encapsulated peptides. A spray drying technique is largely used to achieve microencapsulation in both protein and polysaccharide systems while, generally, liposomes are prepared by a film hydration technique. However, it is seen that the encapsulation efficiency (EE) of peptides using the liposome model is relatively lower since the entropy-driven liposome formation is uncontrolled and spontaneous. Achieving adequate EE through cost effective techniques is indispensable for encapsulation to be applicable to bioactive peptide-based product commercialization. Furthermore, the design of high quality functional foods requires detailed understanding of the release mechanism and kinetics, gastrointestinal stability, bioavailability and physiological bioactivity of the encapsulated peptide products.

Modification of peptide functionality during enzymatic hydrolysis of whey proteins

Peptides derived from food proteins have shown promise as active ingredients for functional food formulation. Due to their reactivity, we evaluated the effects of conditions used for enzymatic hydrolysis of whey protein isolate (WPI) on the functionality of the resulting peptides. Free amino contents were increased when papain and alcalase were used for WPI hydrolysis, but the proteins (especially β-lactoglobulin) were mostly resistant to pepsin activity. The release of peptides during WPI hydrolysis was associated with increase in ferric reducing capacity, but there were also notable decreases in the redox-active sulfhydryl (SH) groups in the papain and alcalase reactions. Apparently, the reducing capacity of the hydrolysates was not dependent on their SH contents, which could have been utilised in disulfide formation. Moreover, considering that the WPI contained 1% lactose and other sugars, we observed that intermediate and advanced Maillard reaction products (MRPs) were formed during WPI hydrolysis, and this can directly impact both the reducing capacity and SH content of peptides. MRPs, such as reductones, can be highly antioxidative and possibly contributed to the reducing capacity observed for the protein hydrolysates, even with the depletion of the SH moieties. A model Maillard reaction with arginine, lactose or glucose, and reduced glutathione was used to confirm SH depletion in the presence of MRPs, and this was attributed to a nucleophilic reaction with carbonyl derivatives generated during the non-enzymatic glycation reaction. Although this can be an opportunity for generating strong redox-active ingredients, it presents some challenges particularly when the native structure of the peptides needs to be conserved for particular biological properties.

Plant Defense Signaling and Responses Against Necrotrophic Fungal Pathogens

Fungal necrotrophic pathogens cause widespread crop losses and infect a variety of plants. The perception of these pathogens or their associated signals by specific receptors in plants triggers the mitogen-activated protein kinase (MAPK) cascades and activates hormone (jasmonates and ethylene)-dependent and hormone-independent signaling, which facilitates the mounting of a defense response against the invading necrotrophs. This response involves the activation of specific transcription factors that result in the production of antifungal proteins (plant defensins) or accumulation of defensive secondary metabolites (phytoalexins). The perception and communication mechanisms triggered by pathogen-associated molecular patterns and the hormones are coordinated by the MAPK signaling cascades which integrate various aspects of the multi-layered plant defense response. This review focuses on compiling distinct and overlapping roles played by various components of the plant signaling machinery in recognizing and mounting a regulated defense response against necrotrophic fungal pathogens.

Peptidomics of Peptic Digest of Selected Potato Tuber Proteins: Post-Translational Modifications and Limited Cleavage Specificity

Bioinformatic tools are useful in predicting bioactive peptides from food proteins. This study was focused on using bioinformatics and peptidomics to evaluate the specificity of peptide release and post-translational modifications (PTMs) in a peptic digest of potato protein isolate. Peptides in the protein hydrolysate were identified by LC-MS/MS and subsequently aligned to their parent potato tuber proteins. Five major proteins were selected for further analysis, namely, lipoxygenase, α-1,4-glucan phosphorylase, annexin, patatin, and polyubiquitin, based on protein coverage, abundance, confidence levels, and function. Comparison of the in silico peptide profile generated with ExPASy PeptideCutter and experimental peptidomics data revealed several differences. The experimental peptic cleavage sites were found to vary in number and specificity from PeptideCutter predictions. Average peptide chain length was also found to be higher than predicted with hexapeptides as the smallest detected peptides. Moreover, PTMs, particularly Met oxidation and Glu/Asp deamidation, were observed in some peptides, and these were unaccounted for during in silico analysis. PTMs can be formed during aging of potato tubers, or as a result of processing conditions during protein isolation and hydrolysis. The findings provide insights on the limitations of current bioinformatics tools for predicting bioactive peptide release from proteins, and on the existence of structural modifications that can alter the peptide bioactivity and functionality.

Preclinical Evidence on the Anticancer Properties of Food Peptides

Natural, synthetic and analogues of peptides have shown prospects for application in cancer chemotherapy. Notably, some food protein-derived peptides are known to possess anticancer activities in cultured cancer cells, and also in animal cancer models via different mechanisms including induction of apoptosis, cell cycle arrest, cellular membrane disruption, inhibition of intracellular signalling, topoisomerases and proteases, and antiangiogenic activity. Although the mechanism of several anticancer food peptides is yet to be clearly elucidated, there is potential for practical applications of the peptides as functional food and nutraceutical ingredients, especially in adjuvant cancer therapy. This review describes the aetiological mechanisms of cancers and the production, structures, mechanisms of action, availability, and cellular and physiological anticancer activities of the food peptides.

Prospects in the use of aptamers for characterizing the structure and stability of bioactive proteins and peptides in food

AbstractFood-derived bioactive proteins and peptides have gained acceptance among researchers, food manufacturers and consumers as health-enhancing functional food components that also serve as natural alternatives for disease prevention and/or management. Bioactivity in food proteins and peptides is determined by their conformations and binding characteristics, which in turn depend on their primary and secondary structures. To maintain their bioactivities, the molecular integrity of bioactive peptides must remain intact, and this warrants the study of peptide form and structure, ideally with robust, highly specific and sensitive techniques. Short single-stranded nucleic acids (i.e. aptamers) are known to have high affinity for cognate targets such as proteins and peptides. Aptamers can be produced cost-effectively and chemically derivatized to increase their stability and shelf life. Their improved binding characteristics and minimal modification of the target molecular signature suggests their suitability for real-time detection of conformational changes in both proteins and peptides. This review discusses the developmental progress of systematic evolution of ligands by exponential enrichment (SELEX), an iterative technology for generating cost-effective aptamers with low dissociation constants (Kd) for monitoring the form and structure of bioactive proteins and peptides. The review also presents case studies of this technique in monitoring the structural stability of bioactive peptide formulations to encourage applications in functional foods. The challenges and potential of aptamers in this research field are also discussed. Graphical abstractAdvancing bioactive proteins and peptide functionality via aptameric ligands

Multiplex Dipstick Technologies for Rapid and Simultaneous Screening of Analytes of Importance in Agri-Food-Nutrition and Health Care: A Review.

Dipstick test kits are being widely used for the rapid screening of a range of antigens or toxins in food, agriculture, and health care. They provide specific results on-site within 10 min with suitable accuracy and are, therefore, cost-effective. Multiplex dipsticks also provide the opportunity for simultaneous detection of multiple antigens in the target sample without using expensive instrumentation, minimizing the cost of analysis as well as the duration of assay. Because of these benefits, dipstick kits are widely being used in the simultaneous detection of several antigens/toxins in large number of samples and in high-throughput manner. This review focuses on the current status of developed multiplex strips and its working principles and future direction of the technology in the agriculture, food, nutrition, and health care sectors.

Nanochemistry of protein-based delivery agents

The past decade has seen an increased interest in the conversion of food proteins into functional biomaterials, including their use for loading and delivery of physiologically active compounds such as nutraceuticals and pharmaceuticals. Proteins possess a competitive advantage over other platforms for the development of nanodelivery systems since they are biocompatible, amphipathic, and widely available. Proteins also have unique molecular structures and diverse functional groups that can be selectively modified to alter encapsulation and release properties. A number of physical and chemical methods have been used for preparing protein nanoformulations, each based on different underlying protein chemistry. This review focuses on the chemistry of the reorganization and/or modification of proteins into functional nanostructures for delivery, from the perspective of their preparation, functionality, stability and physiological behavior.