Current state of insect proteins: extraction technologies, bioactive peptides and allergenicity of edible insect proteins.

This review aims to provide an updated overview of edible insect proteins and the bioactivity of insect-derived peptides. The essential amino acid content of edible insects is compared with well-known protein sources to demonstrate that edible insects have the potential to cover the protein quality requirements for different groups of the population. Then the current methodologies for insect protein extraction are summarized including a comparison of the protein extraction yield and the final protein content of the resulting products for each method. Furthermore, in order to improve our understanding of insect proteins, their functional properties (such as solubility, foaming capacity, emulsifying, gelation, water holding capacity and oil holding capacity) are discussed. Bioactive peptides can be released according to various enzymatic hydrolysis protocols. In this context, the bioactive properties of insect peptides (antihypertensive, antidiabetic, antioxidant and anti-inflammatory properties) have been discussed. However, the allergens present in insect proteins are still a major concern and an unsolved issue for insect-based product consumption; thus, an analysis of cross reactivity and the different methods available to reduce allergenicity are proposed. Diverse studies of insect protein hydrolysates/peptides have been ultimately promoting the utilization of insect proteins for future perspectives and the emerging processing technologies to enhance the wider utilization of insect proteins for different purposes.

In vitro gastrointestinal digestion impact on stability, bioaccessibility and antioxidant activity of polyphenols from wild and commercial blackberries (Rubus spp.).

Gastrointestinal digestion (GID) is a physiological process that transforms the stability, bioaccessibility and antioxidant activity (AOX) of polyphenols from blackberries (Rubus spp.). This study aimed to investigate the effect of the INFOGEST® GID protocol on the phenolic stability, bioaccessibility and AOX of Mexican wild (WB) and commercial (CB) blackberries. After GID, the total phenolic and anthocyanin contents in blackberries decreased by ≥68% and ≥74%, respectively. More than 40 phenolics were identified during GID; most of them degraded completely during digestion. GID had a negative effect on the AOX of both fruits (>50%), but WB showed the highest antioxidant activities, as assessed by the ORAC, DPPH, reducing power and ß-carotene bleaching methods. In Caco-2 cells, the cell-based antioxidant activity of digested blackberries (p < 0.05) decreased by 48% in WB and by 56% in CB. The capacity to inhibit intracellular ROS decreased by 50% in WB and by up to 86% in CB, after digestion. GID is a complex process that impacts on the bioactive properties of food nutrients, especially phenolics. In vitro and cellular AOX of WB polyphenols withstood the gastrointestinal environment better than CB phenolics. The in vitro assays results suggest that phenolics from underutilized WB have a higher bioaccessibility and antioxidant capacity than the polyphenols from the most frequently consumed CB. However, whether this corresponds to a better bioaccessibility in humans remains to be determined in future work.

Growth of Salmonella enterica Serovars Typhimurium and Enteritidis in Iron-Poor Media and in Meat: Role of Catecholate and Hydroxamate Siderophore Transporters.

Enteritidis and Typhimurium are among the top Salmonella enterica serovars implicated in human salmonellosis worldwide. This study examined the individual and combined roles of catecholate-iron and hydroxamate-iron transporters in the survival in meat of Salmonella Enteritidis and Typhimurium. Catecholate-iron-III (Fe3+) and hydroxamate-Fe3+ transporter genes fepA, iroN, and fhuACDB were deleted in isolates of these serovars to generate single, double, and triple mutants. Growth rate in high- and low-iron media was compared among mutants, complements, and their wild-type parents. Susceptibility to 14 antibiotics, the ability to produce and utilize siderophores, and survival on cooked chicken breast were evaluated. In iron-poor liquid media, differences were observed between the growth characteristics of mutant Salmonella Enteritidis and Typhimurium. The double Δ iroNΔ fepA and the triple Δ fhuΔ iroNΔ fepA mutants of Salmonella Enteritidis exhibited prolonged lag phases (λ = 9.72 and 9.53 h) and a slow growth rate (µmax = 0.35 and 0.25 h-1) similar to that of its Δ tonB mutant (λ = 10.12 h and µmax = 0.30 h-1). In Salmonella Typhimurium, double Δ iroNΔ fepA and triple Δ fhuΔ iroNΔ fepA mutations induced a similar growth pattern as its Δ tonB mutant. Double deletions of fepA and iroN reduced the siderophore production and the use of enterobactin as an iron source. In the Δ iroNΔ fepA mutant, but not in Δ fhuΔ iroNΔ fepA, the ferrichrome or deferrioxamine promoted growth for both serovars, confirming the specific role of the FhuACDB system in the uptake and transport of hydroxamate Fe3+. Survival of the mutants was also evaluated in a meat assay, and no difference in survival was observed among the mutants compared with wild type. This study showed differences between serovars in the importance of catecholate-iron and hydroxamate-iron uptake on Salmonella growth in iron-restricted media. Data also confirmed that both Salmonella Enteritidis and Typhimurium are well equipped to survive on cooked chicken meat, offering a rich iron condition.

Protein-Protein Multilayer Oil-in-Water Emulsions for the Microencapsulation of Flaxseed Oil: Effect of Whey and Fish Gelatin Concentration.

The impact of whey protein isolate (WPI) and fish gelatin (FG) deposited sequentially at concentrations of 0.1, 0.5, and 0.75% on the surface of primary oil-in-water emulsions containing 5% flaxseed oil stabilized with either 0.5% fish gelatin or whey protein, respectively, was investigated. The results revealed that the adsorption of WPI/FG or FG/WPI complexes to the emulsion interface led to the formation of oil-in-water (o/w) emulsions with different stabilities and different protection degrees of the flaxseed oil. Deposition of FG on the WPI primary emulsion increased the particle size (from 0.53 to 1.58 µm) and viscosity and decreased electronegativity (from -23.91 to -11.15 mV) of the complexes. Different trends were noted with the deposition of WPI on the FG primary emulsion, resulting in decreasing particle size and increasing electronegativity and viscosity to a lower extent. Due to the superior tension-active property of WPI, the amount of protein load in the WPI primary emulsion as well as in WPI/FG complex was significantly higher than the FG counterparts. A multilayer emulsion made with 0.5% WPI/0.75% FG exhibited the lowest oxidation among all of the multilayered emulsions tested (0.32 ppm of hexanal) after 21 days, likely due to the charge effect of FG that may prevent pro-oxidant metals to interact with the flaxseed oil.