Effects of brown algal phlorotannins and ascorbic acid on the physiochemical properties of minced fish (Pagrosomus major) during freeze-thaw cycles

Protective effects of Bacillus velezensis on texture, physicochemical properties, and lipid oxidation of grass carp fillets during repeated freeze-thaw cycles

BACKGROUND

Probiotics have excellent antioxidant and antibacterial effects and are also considered to be promising natural biological preservatives. This study examined the freeze-thaw stability of the antioxidant and antibacterial activity of probiotic Bacillus velezensis PJP10, and evaluated the effect of different concentrations of PJP10 (106, 107, and 108 CFU mL-1) on microbial growth, textural characteristics, physicochemical properties, and lipid oxidation of grass carp fillets during repeated freeze-thaw cycles.

RESULTS

Freeze-thaw cycles had little effect on the antioxidant and antibacterial stability of PJP10. Treatment with the PJP10 strain slowed effectively the increase in Aeromonas spp. counts (ASC), pH, total volatile basal nitrogen (TVB-N), and thiobarbituric acid (TBA) values of the freeze-thaw fish fillets. It maintained the textural quality of fillets, inhibiting the reduction of hardness, springiness, gumminess, cohesiveness, chewiness, and resilience values, and reduced lipid oxidation, as evidenced by decreased carbonyl values and conjugated diene values after multiple freeze-thaw cycles.

CONCLUSION

Probiotic B. velezensis PJP10 had protective effects on microbiological, textural, and physicochemical properties, and lipid oxidation of grass carp fillets during repeated freeze-thaw storage, suggesting a potential application of this strain in the freeze-thaw preservation of freshwater fish. © 2024 Society of Chemical Industry.

Physicochemical and structural changes of myofibrillar proteins in muscle foods during thawing: Occurrence, consequences, evidence, and implications

Myofibrillar protein (MP) endows muscle foods with texture and important functional properties, such as water-holding capacity (WHC) and emulsifying and gel-forming abilities. However, thawing deteriorates the physicochemical and structural properties of MPs, significantly affecting the WHC, texture, flavor, and nutritional value of muscle foods. Thawing-induced physicochemical and structural changes in MPs need further investigation and consideration in the scientific development of muscle foods. In this study, we reviewed the literature for the thawing effects on the physicochemical and structural characters of MPs to identify potential associations between MPs and the quality of muscle-based foods. Physicochemical and structural changes of MPs in muscle foods occur because of physical changes during thawing and microenvironmental changes, including heat transfer and phase transformation, moisture activation and migration, microbial activation, and alterations in pH and ionic strength. These changes are not only essential inducements for changes in spatial conformation, surface hydrophobicity, solubility, Ca2+ -ATPase activity, intermolecular interaction, gel properties, and emulsifying properties of MPs but also factors causing MP oxidation, characterized by thiols, carbonyl compounds, free amino groups, dityrosine content, cross-linking, and MP aggregates. Additionally, the WHC, texture, flavor, and nutritional value of muscle foods are closely related to MPs. This review encourages additional work to explore the potential of tempering techniques, as well as the synergistic effects of traditional and innovative thawing technologies, in reducing the oxidation and denaturation of MPs and maintaining the quality of muscle foods.

Potential development of non-synthetic food additives from orange processing by-products—a review

Citrus is the largest fruit crop worldwide. Meanwhile, oranges account for 60 per cent of the total, with their main application in juice production. During orange juice production, only about 50 per cent of the fresh orange weight is transformed into juice, with the remaining 50 per cent comprised of residue (peel, pulp, seeds, orange leaves and whole orange fruits that do not reach the quality requirements). With the resulting tons of orange by-products, there has been an initiative to research possible ways to reutilize and revalorize citrus waste. Orange pomace, the by-product from juicing process, is currently used to extract the essential oils for fragrance and flavor, and a majority of the waste is used as cattle feed; however, these applications do not account for all of the waste or capture all of its potential value. Meanwhile, these by-products are put into landfills at the owner’s expense, and contribute to global warming through carbon emissions. On the other hand, orange by-products still contain many useful nutraceutical components, such as dietary fiber and phytochemicals, which could be utilized for value-added ingredients and new product development. Some research approaches in this area include the production of organic fertilizers and biofuels, or the extraction of essential oils, pectins, and antioxidant compounds. There is little information in the literature and in the food industry in terms of utilizing the orange pomace directly or with some simple treatments. Orange pomace may be used for food product development as a ‘clean-label’, non-synthetic preservative, which rationalizes this review.

Effect of freeze-thaw cycles on the quality of quick-frozen pork patty with different fat content by consumer assessment and instrument-based detection

The change in quality of quick-frozen patties containing different amounts of added fat (0%, 5%, 10%, 15%, and 20%) under different freeze-thaw (F-T) cycles (a F-T cycle was performed by freezing at -18 °C and thawing at 4 °C) was evaluated. The results showed that the a*-values of samples were significantly decreased, while L*-values, b*-values, thawing loss, and cooking loss were notably increased after 3 F-T cycles. Low-field nuclear magnetic resonance (LF-NMR) results showed that the water mobility of patties was enhanced. Textural properties (hardness, springiness, cohesiveness, and chewiness) of patties were significantly decreased after 5 F-T cycles (P < 0.05). Lipid and protein oxidation were aggravated with increasing fat content and number of F-T cycles, as confirmed by the increase in lipid peroxides, TBARS, and carbonyl content. Therefore, the results from instrument-based detection and consumer scores indicated that repeated F-T cycles accelerated the quality deterioration of quick-frozen pork patties, and rendered them unacceptable after 3 F-T cycles.

Phlorotannins from Undaria pinnatifida Sporophyll: Extraction, Antioxidant, and Anti-Inflammatory Activities

Undaria pinnatifida sporophyll (U. pinnatifida) is a major byproduct of U. pinnatifida (a brown algae) processing. Its phenolic constituents, phlorotannins, are of special interest due to their intrinsic ability to precipitate proteins. Herein, a high-temperature extraction procedure was used to isolate these biologically active compounds. The heating temperature, heating time, and extraction solvent (ethanol) concentration were examined with response surface analysis to determine the optimal conditions to achieve the maximum extraction rate. The analysis revealed the optimal conditions to be: 170 °C of heating temperature, 5.2 h of heating time, and 52% ethanol concentration for a yield of 10.7 ± 0.2 mg gallic acid equivalent/g dry weight (GAE/g DW) of sample. Compared to epigallocatechin gallate (EGCG), the extracted phlorotannins displayed higher antioxidant activity on H2O2-induced RAW 264.7 cells with improved efficiency. Furthermore, the compounds exhibited strong anti-inflammatory activity. These findings potentially can be utilized to guide development of novel functional foods and food supplements from sea-originated resources such as brown algae.

Effects of Freeze-Thaw Cycles on Gel-Forming Ability and Protein Denaturation in Alaska Pollock Frozen Surimi

Frozen surimi may be damaged by freeze-thaw cycles (refreezing) under various conditions. However, few studies have examined the deterioration of the quality of refrozen surimi. The objective of this study was to determine the deterioration mechanism of refrozen surimi. We used Alaska pollock frozen surimi, which has been studied extensively for gel formation. Refreezing decreased the breaking strength and breaking strain of the heated gel. The length of the line in the diagram between breaking strength and gel stiffness (L value, which indicates the level of change in the breaking strength and gel stiffness with setting time) was also decreased. In contrast, the effect of refreezing on the texture of the gel without the setting process was small. The polymerization rate of myosin heavy chain in refrozen surimi during the setting process was slower than that in nonrefrozen surimi. Additionally, the Ca-ATPase activity of surimi was reduced by approximately 30% with each refreezing. These results demonstrate that the reduction in gel-forming ability by refreezing was caused by the decreased polymerization rate of myosin heavy chain because of myosin head denaturation. We also found that quality deterioration including myofibrillar protein denaturation of frozen surimi occurred mostly during first refreezing rather than during second refreezing. Overall, refreezing and/or repeated refreezing of surimi simply decreased the suwari gel-forming ability without changing the characteristics of surimi. The primary cause of the decrease in gel-forming ability induced by refreezing is considered to be the suppression of myosin heavy-chain polymerization during setting.

Effects of high hydrostatic pressure-assisted thawing on the physicohemical characteristics of silver pomfret (Pampus argenteus)

Effects of high hydrostatic pressure-assisted thawing (HPAT, 100, 150, and 200 MPa) on the physicochemical characteristics of silver pomfret were evaluated in comparison with conventional (water immersion thawing, WIT) thawed samples. HPAT significantly decreased the thawing time, as well as the cooking and total losses. The maximum water holding capacity was observed at 100 MPa. Color changed obviously at ≥150 MPa, resulting in a cooked appearance. Samples thawed with HPAT showed better texture quality and lower lipid oxidation. The levels of myofibrillar protein oxidation and surface hydrophobicity increased, while Ca2+-ATPase activities decreased as the pressure increased. The oxidation of myofibrillar protein was significantly decreased at 100 MPa; total sulfhydryl content was 30.85% higher than that of WIT. Overall, 100 MPa is the optimum treatment condition for silver pomfret thawing without negative effects on quality of the product. HPAT can be a potential alternative to produce high-quality thawed fish.