Mehdi Nikoo

Collagen and Gelatin

Collagen and gelatin have been widely used in the food, pharmaceutical, and cosmetic industries due to their excellent biocompatibility, easy biodegradability, and weak antigenicity. Fish collagen and gelatin are of renewed interest, owing to the safety and religious concerns of their mammalian counterparts. The structure of collagen has been studied using various modern technologies, and interpretation of the raw data should be done with caution. The structure of collagen may vary with sources and seasons, which may affect its applications and optimal extraction conditions. Numerous studies have investigated the bioactivities and biological effects of collagen, gelatin, and their hydrolysis peptides, using both in vitro and in vivo assay models. In addition to their established nutritional value as a protein source, collagen and collagen-derived products may exert various potential biological activities on cells in the extracellular matrix through the corresponding food-derived peptides after ingestion, and this might justify their applications in dietary supplements and pharmaceutical preparations. Moreover, an increasing number of novel applications have been found for collagen and gelatin. Therefore, this review covers the current understanding of the structure, bioactivities, and biological effects of collagen, gelatin, and gelatin hydrolysates as well as their most recent applications.

Antioxidant and cryoprotective effects of Amur sturgeon skin gelatin hydrolysate in unwashed fish mince

Antioxidant and cryoprotective effects of Amur sturgeon skin gelatin hydrolysates prepared using different commercial proteases in unwashed fish mince were investigated. Gelatin hydrolysates prepared using either Alcalase or Flavourzyme, were effective in preventing lipid oxidation as evidenced by the lower thiobarbituric acid-reactive substances formation. Gelatin hydrolysates were able to retard protein oxidation as indicated by the retarded protein carbonyl formation and lower loss in sulfhydryl content. In the presence of gelatin hydrolysates, unwashed mince had higher transition temperature of myosin and higher enthalpy of myosin and actin as determined by differential scanning calorimetry. Based on low field proton nuclear magnetic resonance analysis, gelatin hydrolysates prevented the displacement of water molecules between the different compartments, thus stabilizing the water associated with myofibrils in unwashed mince induced by repeated freeze-thawing. Oligopeptides in gelatin hydrolysates more likely contributed to the cryoprotective effect. Thus, gelatin hydrolysate could act as both antioxidant and cryoprotectant in unwashed fish mince.

The Effects of Deep-Frying, Refrigerated Storage and Reheating on the Fat Content, Oxidation and Fatty Acid Composition of the Fish Rutilus frisii kutum

Fatty acid distribution in the different parts of kutum, Rutilus frisii kutum and the effect of frying and refrigerated storage followed by reheating on lipid oxidation and fatty acid composition in different parts of body flesh were evaluated. Lipid content increased after frying and reheating. In general, saturated fatty acids were higher in anterior parts, while the contents of polyunsaturated fatty acids increased from the anterior to the posterior parts. Frying decreased the contents of unsaturated fatty acids but increased the contents of saturated fatty acids. After refrigerated storage, followed by microwave reheating, the content of polyunsaturated fatty acids decreased, whereas the content of saturated fatty acids increased. The peroxide value increased after frying, compared with that of raw sample. However, the lower PV was obtained in fried-chilled-reheated samples. Frying increased the TBA values and reheating enhanced this increment. Therefore, the frying as well as the refrigerated storage and reheating had the impact on fatty acid composition as well as oxidative stability of kutum fillets.

Postfertilization changes in nutritional composition and protein conformation of hen egg.

Fertilized hen egg is traditionally considered as a dietary supplement in many Asian countries. This work aimed to obtain information on the effect of fertilization on total nutritional composition of egg contents and protein conformation. Chemical analysis showed that the lipid level in fertilized egg began to decrease after day 9. Fertilized egg before day 9 was higher in essential free amino acids (EFAA) and monounsaturated fatty acids (MUFA) contents but lower in cholesterol and polyunsaturated fatty acids (PUFA) than unfertilized counterparts. Fertilized egg proteins were characterized by an increase in hydrophobicity and a decrease in electrostatic interaction. Circular dichroism analysis showed that β-sheet decreased with increasing incubation time, whereas unordered structure increased. The findings observed in this work provide a crucial basis for understanding nutritional composition and protein conformation of fertilized egg, with the potential of being utilized as an EFAA/MUFA-rich, low-cholesterol dietary supplement.

Production of ethanol from Sudanese sugar cane molasses and evaluation of its quality.

The objective of the present study was to produce ethanol from final sugar cane molasses and to evaluate its quality. Urea was used as nitrogen source and added at different concentrations 0.15%, 0.5%, and 0.25% (w/v) to the molasses mash. Experiments were conducted using four treatments depending upon molasses sugar concentration which was calculated as percentages 10, 15, 20 and 25(w/v). The pH of the mash was adjusted to 4.8 using concentrated sulphuric acid. 5% (w/v) baker’s yeast was added. The fermentation was conducted for 72 hours at 33°C. The microbiological analysis revealed absence of bacteria, yeasts and moulds in dilutions 10-3, 10-4, 10-5 of molasses samples. The yield of ethanol obtained was 20 ml per 100 g of molasses, and ethanol with 96% purity could be obtained when the main medium of production (molasses) includes 0.25% (w/v) urea and 20% (w/v) sugar concentration.

Nutritional properties of kutum, Rutilus frisii kutum (Kamensky), silver carp, Hypophthalmichthys molitrix (Val.), and rainbow trout, Oncorhynchus mykiss (Walbaum), correlated with body weight

Abstract The correlation of proximate composition and fatty acid content of the meat of brackish-water kutum, Rutilusfrisii kutum (Kamensky), warm-water silver carp, Hypophthalmichthys molitrix (Val.), and cold-water rainbow trout, Oncorhynchus mykiss (Walbaum) were determined in relation to body weight. In silver carp, body protein increased (r = 0.574, P = 0.032) with increased body weight while moisture decreased (r = -0.789, P = 0.000). In kutum and rainbow trout the contents of protein and lipid were independent of fish size (P > 0.05). The n-3 polyunsaturated fatty acids of silver carp meat increased with body weight (r = 0.592, P = 0.033), while n-6 fatty acids decreased (r =-0.667, P = 0.013). The results indicated the important advantages of the nutritional quality of fish of different sizes in the human diet.

Influence of frying oil type and chill storage on the nutritional quality of farmed great sturgeon (Huso huso)

OBJECTIVE: The objective of this study was to investigate the effect of frying oils (canola, hydrogenated sunflower and soybean oils) available commercially and chill storage on the proximate and fatty acid composition of fried slices of farmed great sturgeon (Huso huso). METHODS: Slices of farmed great sturgeon were fried for four minutes at 160oC in a deep-fryer using different frying oils (canola, hydrogenated sunflower and soybean oils). The oil-to-slice ratio was 2:1. After frying, the slices were allowed to be air cooled for two minutes prior to analysis. For performing the analysis, each of the abovementioned batches was divided into two groups: one group was analysed immediately after frying and the second group was chill-stored at 4oC for three days and then analysed. RESULTS: After frying, the moisture content decreased while that of fat increased. Fatty acid composition of the slices is affected by type of frying oil. Frying increased the omega-6-to-omega-3 (n-6:n-3) fatty acid ratio while decreased Eicosapentaenoic Acid (C20:5 n-3) and Docosahexaenoic Acid (C22:6 n-3) contents. Proximate and fatty acid composition of raw slices did not change after chill storage. However, in fried- and chill-stored slices, Eicosapentaenoic Acid and Docosahexaenoic Acid contents decreased, while linoleic acid content increased. CONCLUSION: The fatty acid composition of the fried slices tended to resemble that of the frying oils, indicating fatty-acid equilibrium between oils and slices and, during chill storage, it is influenced by the type of frying oil. Slices fried with canola oil had omega-6-to-omega-3 ratios in the ranges recommended for human health.