Mastering the art of taming: Reducing bitterness in fish by-products derived peptides

Sensory improvement and antioxidant enhancement in silver carp hydrolysate using prebiotic oligosaccharides: insights from the Maillard reaction

Our previous studies have highlighted the potential of silver carp hydrolysate (SCH) in managing chronic diseases. Unfortunately, its fishy smell and bitter taste limited consumer acceptance. Prebiotic oligosaccharides are often used as dietary supplements, ignoring their role as carbonyl ligands in the Maillard reaction to enhance food's sensory and antioxidant properties. This study aimed to improve SCH's sensory attributes and investigate its physicochemical properties and antioxidant activities using prebiotic oligosaccharides via the Maillard reaction. The results showed that xylo-oligosaccharide (XOS) had the highest reactivity among the oligosaccharides tested, and it greatly enhanced the taste and flavor of SCH, as well as its antioxidant activities (0.45 to 16.5 times). Specifically, XOS effectively reduced the fishy smell and bitter taste, imparting a caramel-like flavor and overall acceptability to SCH. The improved flavor profile was attributed to the increased presence of sulfur-containing and nitrogen oxide volatile flavor compounds, such as benzothiazole, methional, and furans, which also contributed to antioxidant effects. Sensory evaluation results indicated that SCH obtained from papain exhibited a stronger bitter taste than that obtained from alcalase. Additionally, XOS imparted a reddish-brown color to SCH due to the higher browning intensity. This study is the first to demonstrate that XOS in the Maillard reaction can effectively improve the undesirable flavor and taste of SCH while enhancing its antioxidant activities, providing a theoretical basis for developing SCH as a market-acceptable functional food ingredient.

From Waste to Value: Fish Protein Hydrolysates as a Technological and Functional Ingredient in Human Nutrition

Fish provides a low-caloric content, polyunsaturated fatty acids, many essential trace elements and is also a rich source of protein, ranging from 10% to 25%. Therefore, the production of FPH (fish protein hydrolysates) is of great interest, as the resulting products exhibit a variety of important bioactive and technological properties, making them potential ingredients for new functional foods and supplements. The aim of this review was to compile and analyze information on enzymatic hydrolysates, with particular emphasis on those derived from fish by-products, as a potential ingredient in human nutrition. Their nutritional characteristics, food safety aspects, bioactive properties, technological attributes, key influencing factors, and applications in food products were evaluated. The findings revealed that these properties are influenced by several factors, such as the raw material, enzymes used, degree of hydrolysis, and the molecular weight of the peptides, which need to be considered as a whole. In conclusion, the gathered information suggests that it is possible to obtain high-value products through enzymatic hydrolysis, even when using fish by-products. However, although numerous studies focused on FPH derived from fish muscle, research on by-products remains limited. Further investigation is needed to determine whether the behavior of FPH from by-products differs from that of muscle-derived FPH.

Supramolecular self-assembly strategies of natural-based β-lactoglobulin modulating bitter perception of goat milk-derived bioactive peptides

Complete self-assembly and reassembly behavior of bitter peptide-protein necessitates multilevel theories that encompass phenomena ranging from the self-assembly of recombinant complex to atomic trajectories. An extension to the level of mechanism method was put forth, involves limited enzymatic digestion and bottom-up proteomics to dissect inherent heterogeneity within β-LG and β-LG-PPGLPDKY complex and uncover conformational and dynamic alterations occurring in specific local regions of the model protein. Bitter peptide PPGLPDKY spontaneously bound to IIAEKTK, IDALNENK, and YLLFCMENSAEPEQSLACQCLVR regions of β-LG in a 1:1 stoichiometric ratio to mask bitterness perception. Molecular dynamic simulation and free energy calculation provided time-varying atomic trajectories of the recombinant complex and found that a peptide was stabilized in the upper region of the hydrophobic cavity with the binding free energy of -30.56 kJ mol-1 through 4 hydrogen bonds (Glu74, Glu55, Lys69, and Ser116) and hydrophobic interactions (Asn88, Asn90, and Glu112). Current research aims to provide valuable physical insights into the macroscopic self-assembly behavior between proteins and bitter peptides, and the meticulous design of highly acceptable taste characteristics in goat milk products.

Bitter flavors and bitter compounds in foods: identification, perception, and reduction techniques

Bitterness is one of the five basic tastes generally considered undesirable. The widespread presence of bitter compounds can negatively affect the palatability of foods. The classification and sensory evaluation of bitter compounds have been the focus in recent research. However, the rigorous identification of bitter tastes and further studies to effectively mask or remove them have not been thoroughly evaluated. The present paper focuses on identification of bitter compounds in foods, structural-based activation of bitter receptors, and strategies to reduce bitter compounds in foods. It also discusses the roles of metabolomics and virtual screening analysis in bitter taste. The identification of bitter compounds has seen greater success through metabolomics with multivariate statistical analysis compared to conventional chromatography, HPLC, LC-MS, and NMR techniques. However, to avoid false positives, sensory recognition should be combined. Bitter perception involves the structural activation of bitter taste receptors (TAS2Rs). Only 25 human TAS2Rs have been identified as responsible for recognizing numerous bitter compounds, showcasing their high structural diversity to bitter agonists. Thus, reducing bitterness can be achieved through several methods. Traditionally, the removal or degradation of bitter substances has been used for debittering, while the masking of bitterness presents a new effective approach to improving food flavor. Future research in food bitterness should focus on identifying unknown bitter compounds in food, elucidating the mechanisms of activation of different receptors, and developing debittering techniques based on the entire food matrix.

Flavor improving effects of cysteine in xylose-glycine-fish waste protein hydrolysates (FPHs) Maillard reaction system

A promising way to utilize fish by-products is to develop hydrolysis of fish proteins with enzymes. The obtained fish protein hydrolysates (FPHs) are rich in peptides and amino acids, but bitterness and aroma defects impede further utilization of FPHs. The present study adopted Maillard reaction to improve FPHs' flavor and illustrated the role of cysteine in this system. We investigated the impact of cysteine (0, 0.25%, 0.5%, 0.75%, and 1%) on the browning intensity, free amino acids (FAAs), molecular weight distribution, structure of MRPs, volatile compounds changes and organoleptic characteristics of xylose-glycine-FPHs Maillard reaction systems. Results showed that the addition of cysteine lowered the browning degree of Maillard reaction products (MRPs) by inhibiting the cross-linking of small peptides and reducing the production of melanin. GC-MS and GC-IMS analysis indicated that cysteine inhibited the formation of furans and nitrogen-containing compounds and facilitated the formation of sulfur-containing compounds contributing to the meaty flavor. Sensory analysis revealed that 0.25-0.75% range of cysteine increased the meaty, caramel, umami, mouthfulness and salty notes, and caused a decrease in bitter taste of the MRPs as confirmed by GC-MS. A highly significant correlation between the organoleptic characteristics and physicochemical indicators of MRPs was found by Mantel test. These results elucidated the influence of cysteine on the formation of Maillard reaction products and will help improve the flavor profile of meat flavorings.