Rheological and Biochemical Characterization of Salmon Myosin as Affected by Constant Heating Rate

Structural and aggregation changes of silver carp myosin induced with alcohols: Effects of ethanol, 1,2-propanediol, and glycerol

This study investigated the effects of ethanol, 1,2-propanediol, and glycerol on the structure and aggregation behavior of silver carp (Hypophthalmichthys molitrix) myosin. All alcohols induced extensive alteration in the tertiary structure of myosin. Both ethanol and 1,2-propanediol further promoted an increase in the content of β-sheets in myosin and induced myosin aggregation. While glycerol had almost no impact on the secondary structure of myosin. Molecular dynamics simulations revealed that increasing the concentration of ethanol and 1,2-propanediol affected the overall structural changes in the myosin heavy chain (MHC), while glycerol exerted a more pronounced effect on the MHC tail when compared to the MHC head. Disruption of the hydration layers induced by ethanol and 1,2-propanediol contributed to local structural changes in myosin. Glycerol at a concentration of 20% induced the formation of a larger hydration layer around the MHC tail, which facilitated the stabilization of the protein structure.

Study on the mechanism of soy protein isolate to improve quality of reduced-salt Hypophthalmichthys molitrix surimi gel: Focus on gel quality, protein structure, and in vitro digestibility

Excessive intake of sodium chloride may bring a series of diseases; as a result, reduced-salt surimi gels have gained growing popularity for sodium reduction. This paper studied soy protein isolate (SPI, 2.0%, 4.0%, and 6.0%, w/w) as a gel enhancer for reduced-salt silver carp surimi. Compared with the control (2.0% NaCl), the addition of SPI significantly increased (P < 0.05) the total SH content, hydrophobic interaction force, disulfide bond, hardness, gel strength, and water-holding capacity of the gels. During the thermal denaturation process, SPI and myofibrillar protein jointly participated in the formation of the gel network, resulting in a G' value increase at 90 °C, forming a denser/more stable gel network structure. In vitro pepsin digestion results showed the digestibility of the reduced-salt gel with SPI was higher than that of the control. Therefore, appropriate SPI addition can improve the gel performance of reduced-salt surimi gel without affecting digestion and absorption.

Standardized amino acid digestibility and nitrogen-corrected true metabolizable energy of frozen and freeze-dried raw dog foods using precision-fed cecectomized and conventional rooster assays

Commercial raw or minimally-processed diets, often referred to holistically as raw meat-based diets (RMBD) represent a small portion of the pet food market, but the growth of this sector has been significant in recent years. While traditionally, high-moisture, frozen options were the standard format of commercially available raw diets, freeze-dried raw diets have become more prevalent as of late. Despite the increasing popularity of these commercial raw diet formats, there is a dearth of literature describing their nutritional properties, particularly regarding freeze-dried diets. Therefore, the objective of this experiment was to determine and compare the standardized amino acid (AA) digestibilities and nitrogen-corrected true metabolizable energy (TMEn) of raw frozen and freeze-dried dog foods using precision-fed cecectomized and conventional rooster assays. Three formats of frozen or freeze-dried raw diets provided by Primal Pet Foods (Fairfield, CA, USA) were tested: traditional freeze-dried nuggets (T-FDN), hybrid freeze-dried nuggets (H-FDN), and frozen nuggets (FZN). Diets were fed to cecectomized roosters (4 roosters/diet) to determine AA digestibilities, while conventional roosters (4 roosters/diet) were used to determine TMEn. In both cases, after 26 h of feed withdrawal, roosters were tube-fed 12 to 13 g of test diets and 12 to 13 g of corn. Following crop intubation, excreta were collected for 48 h. Endogenous corrections for AA were made using five additional cecectomized roosters. All data were analyzed using the Mixed Models procedure of SAS version 9.4. There were no significant differences in standardized AA digestibilities among diets, with digestibilities being high for all diets tested. For most of the indispensable AA, digestibilities were greater than or equal to 90% for all diets. Histidine and lysine were the exceptions, with digestibilities ranging from 82% to 87% and 87% to 92%, respectively. Moreover, the reactive lysine:total lysine ratio, a measure of heat damage, ranged from 0.91 to 0.95. TMEn values were higher (P = 0.0127) in T-FDN (6.1 kcal/g) and FZN (5.9 kcal/g) than H-FDN (5.3 kcal/g) and were most similar to those estimated by Atwater factors. In general, all diets tested had high AA digestibilities and had TMEn values that were most similar to Atwater factors.

Gel performance of surimi induced by various thermal technologies: A review

Heating is a vital step in the gelation of surimi. Conventional water bath heating (WB) has the advantages of easy operation and low equipment requirements. However, the slow heat penetration during WB may lead to poor gel formation or gels prone to deterioration, especially with one-step heating. The two-step WB is time-consuming, and a large amount of water used tends to cause environmental problems. This review focuses on key factors affecting the quality of surimi gels in various heating technologies, such as surimi protein structure, chemical forces, or the activity of endogenous enzymes. In addition, the relationships between these factors and the gel performance of surimi under various heating modes are discussed by analyzing the heating temperature and heating rate. Compared with WB, the gel performance can be improved by controlling the heating conditions of microwave heating and ohmic heating, which are mainly achieved by changing the molecular structure of myofibrillar proteins or the activity of endogenous enzymes in surimi. Nevertheless, the novel thermal technologies still face several limitations and further research is needed to realize large-scale industrial production. This review provides ideas and directions for developing heat-induced surimi products with excellent gel properties.

Effect of different drying methods on the myosin structure, amino acid composition, protein digestibility and volatile profile of squid fillets

The impacts of freeze drying (FD), hot-air drying (AD), and heat pump drying (HPD) on myosin structure, amino acid composition, protein digestibility and volatile compounds of squid (Todarodes pacificus) fillets were evaluated. Freeze-dried squids showed similar amino acid composition to that of raw squids, but differed from that of AD and HPD samples. The percentage of in vitro digestibility followed the order of FD (76.81%)>HPD (70.51%)>raw (67.99%)>AD (61.47%) samples. AD caused more damage to squid myosin structure than HPD, while FD effectively retained the myosin integrity. Drying decreased total number of volatile compounds, but increased the content of total volatile compounds based on GC × GC-TOFMS results. HPD and AD samples had the highest and lowest total numbers and contents of volatiles, respectively. In general, FD provided squids with the best quality, followed by HPD. Considering the production cost and product quality, HPD demonstrated the potential for industrial application.