Changes in the digestion properties and protein conformation of sturgeon myofibrillar protein treated by low temperature vacuum heating during in vitro digestion.

The digestion properties of sturgeon myofibrillar protein (MF) treated by low temperature vacuum heating (LTVH) at different processing temperatures (50, 60 and 70 °C) and times (15 and 30 min) were studied and compared with those of sturgeon MF treated by traditional cooking (TC). The results showed that as the temperature and time increased, the protein digestibility decreased, whereas the particle size and protein aggregation increased. It was observed that the band intensity of myosin heavy chain and myosin heavy chain 7 weakened; however, the band intensity of actin showed little change. MALDI-TOF-MS analysis revealed that the digested products of the samples treated by LTVH had a larger proportion of 750-1000 Da peptides than those treated by TC, which was consistent with the trend of the number of unique peptides identified in each group. Fourier transmission infrared (FT-IR) spectroscopy showed that the contents of α-helices and ß-sheets exhibited negative and positive correlations with the temperature, respectively. Overall, compared to TC, LTVH can relieve the heat stress of protein conformation, reduce protein aggregation to improve the accessibility of the protein to digestive protease, and increase digestibility.

A Pilot Safety Assessment for Recombinant Epinephelus lanceolatus Piscidin Yeast Powder as a Drug Food Additive after Subacute and Subchronic Administration to SD Rats.

Recombinant Epinephelus lanceolatus piscidin (RELP) was previously shown to improve growth performance and immune response when used as a feed additive for Gallus gallus domesticus. However, the long-term toxicity of RELP has not be thoroughly investigated. In the present study, we evaluated the subacute and subchronic oral toxicities of RELP in SD rats by hematological, biochemical, and histopathological analyses. To determine subacute and subchronic toxicities, male and female rats were fed with RELP 1000 mg/kg bodyweight/day for 28 and 90 days, respectively. Bodyweight and food intake were unchanged by RELP treatment over the course of the studies. After exposure, samples of blood, heart, lung, liver, and kidney were collected and analyzed. Results demonstrated that RELP exposure did not cause any observable hematological, biochemical, or histological abnormalities in SD rats. Thus, RELP may be a safe feed additive for use in agriculture and aquaculture.

Herring Milt and Herring Milt Protein Hydrolysate Are Equally Effective in Improving Insulin Sensitivity and Pancreatic Beta-Cell Function in Diet-Induced Obese- and Insulin-Resistant Mice.

Although genetic predisposition influences the onset and progression of insulin resistance and diabetes, dietary nutrients are critical. In general, protein is beneficial relative to carbohydrate and fat but dependent on protein source. Our recent study demonstrated that 70% replacement of dietary casein protein with the equivalent quantity of protein derived from herring milt protein hydrolysate (HMPH; herring milt with proteins being enzymatically hydrolyzed) significantly improved insulin resistance and glucose homeostasis in high-fat diet-induced obese mice. As production of protein hydrolysate increases the cost of the product, it is important to determine whether a simply dried and ground herring milt product possesses similar benefits. Therefore, the current study was conducted to investigate the effect of herring milt dry powder (HMDP) on glucose control and the associated metabolic phenotypes and further to compare its efficacy with HMPH. Male C57BL/6J mice on a high-fat diet for 7 weeks were randomized based on body weight and blood glucose into three groups. One group continued on the high-fat diet and was used as the insulin-resistant/diabetic control and the other two groups were given the high-fat diet modified to have 70% of casein protein being replaced with the same amount of protein from HMDP or HMPH. A group of mice on a low-fat diet all the time was used as the normal control. The results demonstrated that mice on the high-fat diet increased weight gain and showed higher blood concentrations of glucose, insulin, and leptin, as well as impaired glucose tolerance and pancreatic ß-cell function relative to those on the normal control diet. In comparison with the high-fat diet, the replacement of 70% dietary casein protein with the same amount of HMDP or HMPH protein decreased weight gain and significantly improved the aforementioned biomarkers, insulin sensitivity or resistance, and ß-cell function. The HMDP and HMPH showed similar effects on every parameter except blood lipids where HMDP decreased total cholesterol and non-HDL-cholesterol levels while the effect of HMPH was not significant. The results demonstrate that substituting 70% of dietary casein protein with the equivalent amount of HMDP or HMPH protein protects against obesity and diabetes, and HMDP is also beneficial to cholesterol homeostasis.

Debittering of salmon (Salmo salar) frame protein hydrolysate using 2-butanol in combination with ß-cyclodextrin: Impact on some physicochemical characteristics and antioxidant activities.

Impacts of 2-butanol and ß-cyclodextrin (ß-CD) at various ratios and treatment times on bitterness, physicochemical and functional properties of Alcalase salmon frame protein hydrolysate (ASF) were investigated. ASF treated with 2-butanol at a ratio of 1:4 (w/v) for 20 min (ASFB) or with ß-CD at a ratio of 1:1 (w/w) for 30 min (ASF-C-1) had lower bitterness score than ASF (p < 0.05). Bitterness score of ASF (8.45) was reduced to the lowest score (1.32) when ASFB was subsequently treated with ß-CD at a 1:1 ratio (w/w) for 30 min (ASFB-C-1). Surface hydrophobicity of all debittered samples was lower than that of ASF sample (p < 0.05). The level of aromatic amino acids-containing peptides was reduced in ASFB-C-1 as shown by gel permeation chromatography. ASFB-C-1 sample had higher overall-likeness score but lower antioxidant properties than ASF (p < 0.05). The desired antioxidant activity could be achieved via increasing the amount of protein hydrolysate without imparting undesirable taste.

Nutritional Characterization of Sea Bass Processing By-Products.

The consumption of functional foods and nutraceuticals is gaining more importance in modern society. The exploration of alternative sources and the utilization of by-products coming from the food industry are gaining more importance. The present study aimed to characterize the nutritional value and potential use of sea bass by-products as a source of high-added-value compounds for the development of supplements. The chemical composition (moisture, protein, fat, and ash contents) and profiles of amino acids (high-performance liquid chromatography coupled to a scanning fluorescence detector), fatty acids (gas chromatography coupled to a flame ionization detector), and minerals (inductively coupled plasma optical emission spectroscopy) were determined for sea bass fillet and its by-products (skin, guts, gills, liver, head, and fish bones). The chemical composition assays revealed that by-products were rich sources of proteins (skin; 25.27 g/100 g), fat (guts and liver; 53.12 and 37.25 g/100 g, respectively), and minerals (gills, head, and fish bones; 5.81, 10.11, and 7.51 g/100 g, respectively). Regarding the amino-acid profile, the skin and liver were the main sources of essential amino acids with an essential amino-acid index of 208.22 and 208.07, respectively. In the case of the fatty-acid profile, all by-products displayed high amounts of unsaturated fatty acids, particularly monounsaturated (from 43.46 to 49.33 g/100 g fatty acids) and omega-3 fatty acids (in the range 10.85-14.10 g/100 g fatty acids). Finally, the evaluation of mineral profile indicated high contents of calcium and phosphorus in gills (1382.62 and 742.60 mg/100 g, respectively), head (2507.15 and 1277.01 mg/100 g, respectively), and fish bone (2093.26 and 1166.36 mg/100 g, respectively). Therefore, the main sources of monounsaturated, unsaturated, and long-chain omega-3 fatty acids were guts and liver. The most relevant source of minerals, particularly calcium, phosphorus, and manganese, were head, fish bones, and gills. The most promising source of proteins and amino acids was the skin of sea bass.

Effects of l-arginine and l-histidine on heat-induced aggregation of fish myosin: Bighead carp (Aristichthys nobilis).

This research focused on the effects of l-arginine (l-Arg) and l-histidine (l-His) on the heat-induced aggregation of fish myosin. l-Arg/l-His increased the pH of the myosin solution from 6.82 to 8.74 and 7.24, respectively, and decreased the turbidity, aggregate size, shear modulus, and breaking force. The incorporation of l-Arg/l-His decreased the surface hydrophobicity during setting, but increased it during the two-step heating. The heat-induced aggregation of myosin was suppressed by both amino acids, with the inhibitory effect being greater for l-Arg than l-His. On one hand, the change in the pH played a critical role in suppressing the heat-induced aggregation of myosin. On the other hand, the characteristics of l-Arg/l-His themselves, such as net charges and particular R-groups, were another main contributor to aggregation suppression. Particularly, l-Arg/l-His could interact with exposed aromatic residues of myosin, and the interactions may dominate and overwhelm the burial of aromatic residues during two-step heating.

Purification and characterization of a sarcoplasmic serine proteinase from threadfin bream Nemipterus virgatus muscle.

A sarcoplasmic serine proteinase (SSP) was purified from threadfin bream (Nemipterus virgatus) belly muscle by ammonium sulfate precipitation and a series of chromatographies including Q-Sepharose, Phenyl Sepharose and Superdex 200. The SSP was purified 1967 folds with a yield of 4.8%. The molecular weight of the SSP was estimated to be 43.5 kDa and 22.5 kDa on SDS-PAGE under non-reducing and reducing conditions, respectively. The N-terminal amino acid sequence of the two protein bands were determined as IVGGYEXQPYSQAHQVSLNSGY and corresponded. It is suggested that the SSP exists as a homodimer. Optimum pH and temperature were 9.5 and 50 °C, using Boc-Val-Pro-Arg-MCA as a substrate. Substrate specificity and effects of inhibitors indicated that the SSP was a trypsin-like serine proteinase. The SSP was responsible for hydrolyzing myosin heavy chain (MHC) and inducing modori phenomenon in the threadfin bream surimi gel. Thus, the SSP was considered as a modori-inducing proteinase.

Diet-induced obesity and associated disorders are prevented by natural bioactive type 1 fish collagen peptides (Naticol®) treatment.

To fight against metabolic disorders such as insulin resistance, new alimentary behaviors are developed. For instance, hyperproteined, gluten-free, or collagen-enriched diets could be preconized in order to reduce the consequences of obesity. In this aim, this study evaluates the potential effects of warm sea fish collagen peptides (Naticol®) on representative metabolic and inflammatory parameters. For that, male C57Bl6/J mice fed with either a chow- (CD) or high-fat diet (HFD) were submitted or not to specific collagen peptides in drinking water (4 g/kg bw/d) for 20 weeks. Weight, body composition, glucose tolerance, and insulin sensitivity were followed up. Effects of fish collagen peptides on various blood parameters reflecting the metabolism status were also measured (free fatty acids, triglycerides, cholesterol, hormones) together with adipocyte inflammation. Results showed that HFD-fed mice supplemented by fish collagen peptides exhibited a significant lower increase in body weight as soon as the twelfth week of treatment whereas no effect of the peptide was observed in CD fed mice. In line with this result, a weaker increase in fat mass in HFD-fed mice supplemented with Naticol® at both 9 and 18 weeks of treatment was also observed. In spite of this resistance to obesity promoted by fish collagen peptides treatment, no difference in glucose tolerance was found between groups whereas mice treated with Naticol® exhibited a lower basal glycemia. Also, even if no effect of the treatment on adipocyte lipolysis was found, a decrease of inflammatory cytokines was retrieved in collagen-supplemented group arguing for a potential better insulin sensitivity. Altogether, these results need to be completed but are the first describing a benefic role of warm sea fish collagen peptides in a context of metabolic disease paving the route for a potential utilization in human obesity-associated disorders.

Effects of dietary replacement of fishmeal by mealworm meal on muscle quality of farmed shrimp Litopenaeus vannamei.

This study investigated the muscle quality of the shrimp Litopenaeus vannamei fed on a diet containing different proportions of mealworm meal (MW) (0, 25, 50, 75 and 100%) as a substitute for fishmeal, which is the normal diet used in shrimp commercial production. The proximate composition, fatty acid profile, colour and texture of the shrimps were evaluated. Moisture, protein, and ash content of shrimp muscle were not significantly altered when fishmeal was replaced by MW (p>0.05). However, the replacement resulted in a linear increase in lipid content (p<0.05). The fatty acid composition of the experimental diets directly mirrored the fatty acid composition of shrimp muscle. The absence of long-chain polyunsaturated fatty acids in MW composition resulted in a linear decrease in eicosapentaenoic and docosahexaenoic fatty acids in shrimp muscle with increasing levels of MW in the diet. The n-3/n-6 ratio ranged from 0.50 to 0.67. Colour and firmness were unchanged between the treatments. Although the use of MW as a fishmeal substitute in L. vannamei diets has affected the lipid and fatty acid composition of shrimp muscle, from a human nutritional perspective, the lipid content of the shrimps is considered low and the n-3/n-6 ratio remained within the human dietary requirements. Therefore the use of a mealworm diet for shrimp production is a viable alternative to increasingly expensive fishmeal based diets.