Sustainable Upcycling of Fisheries and Aquaculture Wastes Using Fish-Derived Cold-Adapted Proteases

The fisheries and aquaculture industries are some of the major economic sectors in the world. However, these industries generate significant amounts of wastes that need to be properly managed to avoid serious health and environmental issues. Recent advances in marine waste valorization indicate that fish waste biomass represents an abundant source of high-value biomolecules including enzymes, functional proteins, bioactive peptides, and omega-3 rich oils. Enzyme-assisted processes, for the recovery of these value-added biomolecules, have gained interest over chemical-based processes due to their cost-effectiveness as well as their green and eco-friendly aspects. Currently, the majority of commercially available proteases that are used to recover value-added compounds from fisheries and aquaculture wastes are mesophilic and/or thermophilic that require significant energy input and can lead to unfavorable reactions (i.e., oxidation). Cold-adapted proteases extracted from cold-water fish species, on the other hand, are active at low temperatures but unstable at higher temperatures which makes them interesting from both environmental and economic points of view by upcycling fish waste as well as by offering substantial energy savings. This review provides a general overview of cold-adapted proteolytic enzymes from cold-water fish species and highlights the opportunities they offer in the valorization of fisheries and aquaculture wastes.

Characterization of pecan shells and their effect on the physical properties and acceptability of smoked chicken breast

Pecan shells were used as a source of smoke for cooked chicken breast and compared with samples smoked with hickory, mesquite, and apple tree wood. The wood moisture content ranged from 7.94% to 11.43%, whereas ash ranged from 0.97% to 3.11%. The particle size varied among the smoke sources, with chopped pecan shells having more pieces in the "coarse" category. Several properties related to quality of the cooked meat were measured including moisture content, water activity, color, cook loss, expressible moisture, and maximum shear force. Moisture content ranged from 70.13% to 71.72%, whereas pH ranged from 6.39 to 6.43. Chicken breasts smoked with pecan shells were darker (L^* = 72.86 compared to 74.94 to 76.57) and slightly redder (a^* = 5.71; b^* = 25.70) than other samples. Color development was localized to the surface of the meat. Cooking loss did not differ significantly among the samples (26.13% to 27.03%) nor did expressible moisture (9.68% to 11.87%). Meat tenderness was assessed by shear values, but did not differ among the samples. Consumer panels showed that all samples were well liked. Samples smoked with mesquite had slightly lower scores for flavor and overall likability, whereas the scores for samples smoked with hickory, apple, or pecan shells were no different. PRACTICAL APPLICATION: Many meat products are cooked in the presence of smoke produced from burning hardwoods. This work shows that smoke can be produced from waste pecan shells, resulting in chicken breast with similar yield, texture, moisture retention, and acceptability as that smoked with hickory, mesquite, or apple tree wood.

Effect of marinating ingredients on temperature-induced denaturation of hemoglobin and its relation to red blood spot formation in cooked chicken breast

Red blood spot (RBS) commonly found in cooked chicken breast has caused severe economic loss as it is perceived as a sign of undercooked product. The objectives of this study were to investigate the cause of RBS as related to common ingredients used in marination, based on both chicken breast and isolated chicken hemoglobin (Hb) models. The effect of sodium chloride (NaCl), sodium tripolyphosphate (STPP), and glucose on thermal denaturation of Hb was investigated along with the extent of RBS formation in cooked marinated chicken breast. After vacuum tumbling for 65 min and subsequent storage at 4 °C for 20 hr, STPP and glucose were not absorbed into the center of chicken breast. However, Na⁺ was absorbed after 12 hr storage. The denaturation temperature (T_d ) of isolated chicken Hb decreased to 65.8 °C in the presence of 1.5 M NaCl, while that of the control was 69.4 °C. STPP at pH 9 decreased T_d of Hb to 61.4 °C. The alkaline pH induced by STPP destabilized the Hb structure. RBSs were observed at 100% incidence when cooked to core temperatures of 50 and 70 °C for 1 min. RBSs were completely eliminated at core temperature of 85 °C. The ingredients used during marination appeared to have a minimal effect on RBS formation due to their limited absorption into the chicken breast. The cooking temperature is a major factor governing RBSs, as it directly affects the denaturation of Hb.

Extraction and physicochemical characterization of broiler (Gallus gallus domesticus) skin gelatin compared to commercial bovine gelatin

Gelatin was extracted from broiler (Gallus gallus domesticus) skins and analyzed to compare its physicochemical properties with those of commercial bovine gelatin. The average yield of broiler skin gelatin was 6.5% on a wet weight basis. Broiler skin gelatin had more α1-and α2-chains than β-chain and contained high molecular weight (γ-chain) polymers. Glycine was the dominant amino acid in broiler skin gelatin (20.26%), followed by proline (Pro) (15.12%) then hydroxyproline (Hyp) (11.36%). Compared to commercial bovine gelatin, broiler skin gelatin had less total imino acids (Pro and Hyp) but a higher (33.65 vs. 31.38°C) melting temperature (P < 0.01). The differences in physical properties between the broiler and commercial bovine gelatins appeared to be associated with differences in their amino acid composition and molecular weight distribution. The sensory evaluation results revealed that broiler skin gelatin could be a potential alternative to commercial bovine gelatin, useful in various food products.