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Warmed-over flavor (WOF) is an off-flavor in surimi gels. Yeast extract (YE) could improve the aroma properties of food. However, the effect of YE on the WOF in surimi gels and its mechanism was still unclear. In this study, aroma profiles, the composition of aroma compounds and aroma precursors, concentrations of WOF compounds, and thiobarbituric acid reactive substances (TBARS) of surimi gels with different amounts of YE were investigated by molecular sensory science and chromatographic techniques. Moreover, the effect of pyrazines and esters introduced by YE on WOF was also tested by sensory analysis. The addition of no less than 1% YE to surimi gels significantly weakened WOF. However, YE did not decrease the concentrations of WOF compounds and did not change the fatty acid composition and TBARS in surimi gels. Conversely, the addition of YE significantly increased the contents of free amino acids, N-containing compounds, and esters in surimi gels. The contents of total free amino acids, 2,6-dimethylpyrazine, and ethyl acetate in surimi gels with 2.5% YE were 1.5, 21, and 2.1 times higher than those in the control, respectively. Additionally, the sensory results of the spiked aroma models containing WOF compounds, 2,6-dimethylpyrazine, and esters showed that more than 9.4 µg/kg of 2,6-dimethylpyrazine with a baked-potato note and more than 6.1 µg/kg of ethyl acetate and 11.2 µg/kg of butyl acetate with a fruity note could significantly mask WOF. In conclusion, WOF in surimi gels could be masked by YE due to the high concentrations of pyrazines and esters. Practical Application: Yeast extracts could decrease the warmed-over flavor (WOF) due to the high concentrations of pyrazines (baked-potato note) and esters (fruity note). This finding extends the application of yeast extracts in the food industry. On the other hand, this study presents a reasonable solution for the reduction of WOF in surimi products.

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The effects and reasons of perilla juice (PJ) and ginger juice (GJ) on the reduction of "warmed-over flavor" (WOF) in surimi gels were revealed by detecting odor profiles and protein and lipid oxidation degrees of surimi gels, concentrations and odor activity values (OAVs) of WOF compounds. Adding PJ and GJ to surimi gels significantly reduced the WOF and improved the fish fragrance odor, but sodium ascorbate (SA) only weakened the WOF. The (E,E)-2,4-heptadienal's OAVs in the PJ and GJ groups were decreased by >50% compared with the control check (CK) and SA groups. Meanwhile, surimi gels added with PJ and GJ presented lower lipid and protein oxidation degrees. The verification test indicated that PJ and GJ's aroma had a masking effect on the WOF. In conclusion, PJ and GJ reduced the WOF in surimi gels by preventing WOF compounds' production and masking the WOF with their distinct aroma.

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This study revealed the variations in odor characteristics and underlying mechanisms of different cross-linked surimi gels under liquid nitrogen (LN) spray freezing. The results demonstrated that LN spray freezing had an essential effect on the gels' odor. The odor changes in the -80 °C LN spray freezing group were closer to the control group, while -35 °C LN spray freezing treatment had the greatest impact on the aroma quality of gels. Freezing reduced gels' texture properties, intensified lipid and protein oxidation, altered protein conformation, increased surface hydrophobicity and hydrophobic interactions. These changes affected the gels' odor characteristics, leading to a reduction in fish aroma and an increase in fishy and oil odors after freezing. These tendencies were more pronounced at -35 °C LN spray freezing with lower cross-linking degrees, and reducing the freezing temperature to -80 °C and increasing the cross-linking degree to 62.99% mitigated the extent of deterioration in gel flavor quality.

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The study investigated the effect of material temperatures (15°C, 20°C, 25°C, 30°C, 35°C, and 40°C) on the quality of fish vermicelli (FV) in terms of morphological, cooking, textural, microstructural, and water distribution properties. Results showed that as the material temperatures increased, the surface smoothness, cooking characteristics, and textural properties of FV significantly increased, followed by a decrease. Especially, when the material temperatures were 25°C and 30°C, the FV samples exhibited denser and more continuous gel networks with more embedded starch particles, resulting in decreased cooking loss and improved tensile strength. However, at material temperatures above 35°C, the continuity of the protein phase was disrupted by overswelling starch granules, leading to the worst cooking characteristics and textural properties. Especially at material temperatures of 40°C, the water holding capacity, hardness, and springiness of FV decreased by 25.59%, 73.48%, and 47.98%, respectively, compared to the samples at 25°C. Additionally, the cooking loss increased by 91.40%. In conclusion, the critical material temperature for the quality deterioration of FV was 35°C, and it was recommended to produce FV below this temperature.

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This study investigated the effects of chemical composition of surimi (prepared by 0, 1, or 2 times of rinsing) and gelling temperature (90 °C and 100 °C) on the odor characteristics of surimi products and the relationship between the chemical composition of surimi and the aroma of surimi products. The once- and twice-rinsed surimi showed a decrease (p < 0.05) of 71.32%, 74.60%, 42.79% and 61.12% in the contents of total amino acids and total fatty acids, respectively. The surimi products prepared with un-rinsed surimi at 90 °C had the highest fish-fragrance score, while those prepared with once-rinsed surimi at 100 °C showed the strongest warmed-over flavor (WOF) and the lowest fish-fragrance score.Gly, Phe, and most of the saturated fatty acids were associated with WOF formation in surimi products, while Leu, Ile, Val, Asp, and unsaturated fatty acids were positively related to their fish-fragrance note.

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BACKGROUND: The physical factors associated with musculoskeletal pain in nursing personnel have been largely investigated, although the role of sleep and psychological factors resulting in musculoskeletal pain has not been addressed thoroughly. OBJECTIVE: This study aimed to explore the prevalence of musculoskeletal pain and investigate how sleep and psychological factors influence musculoskeletal pain in a nursing group. METHODS: Nordic standard questionnaires were distributed to 230 female nurses. Chi-square tests were performed to assess the associations between sleep problems, psychological problems, and musculoskeletal pain symptoms. Binary logistic regression analysis was also conducted to identify the primary factors influencing the prevalence of musculoskeletal pain. RESULTS: The highest prevalence of pain was observed in the lower back, neck, and shoulders, whereas the lowest prevalence of pain was observed in the ankles, feet, elbows, and hips/buttocks. Chi-square analysis and binary logistic regression showed that sleep duration, sleep onset time, and sleep quality all significantly contributed to the development of neck and upper back pain. With regard to the psychological factors, only occupational pride and stress had a significant effect on pain; in contrast, family support did not show any significant influence. CONCLUSION: Compared with other body regions, musculoskeletal pain in the lower back, neck, and shoulders requires more attention and preventive interventions. Special efforts should be made to shift the workday system of the nursing group because of the strong correlation between sleep problems and pain. Incentives other than penalty mechanisms should be considered seriously in nursing to boost occupational pride and relieve job stress.

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This study investigated the effects of surimi to soybean flour ratio (0:10, 1:9, 2:8, 3:7, 4:6) on the physicochemical characteristics and flavor properties of dual-proteins extrudates. The increasing ratio of surimi improved the color of extrudates and raised the apparent viscosity of the mixed raw materials, which led to the decrease of extrudates' thickness. The excess ratio of surimi and soybean flour (more than 2:8) was bad for extrudates' physicochemical characteristics with sharply decreased tensile strength, macroscopic longitudinal fracture, broken and unevenly distributed microstructure, increased water mobility and decreased free water content. However, the increasing ratio of surimi had no effect on the protein secondary structure of extrudates. Sensory evaluation, E-tongue and E-nose analysis suggested that adding surimi significantly changed the flavor properties of extrudates, with increased sweetness and umami taste, and an appropriate ratio (2:8 or 3:7) could reduce the beany flavor and without an obvious fishy off-flavor.

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To investigate the effects of inoculation fermentation on the quality of Zhayu (a traditional fermented fish product in China), different amounts of L. plantarum, P. acidilactici, and P. pentosaceus were inoculated into samples, and the safety, nutritional, textural, and flavor properties of the samples were evaluated. Fermentation with lactic acid bacteria (LAB) decreased pH values and total volatile basic nitrogen content. The addition of 108~109 cfu/100 g LAB significantly increased the content of crude fat and water-soluble proteins in Zhayu. The addition of L. plantarum and P. acidilactici increased the content of soluble solids in Zhayu. Moreover, fermentation with LAB made the products tender and softer, and the samples prepared with 109 cfu/100 g LAB presented better overall qualities. Additionally, Zhayu fermented with L. plantarum and P. acidilactici showed the strongest sourness, while the samples prepared with P. pentosaceus showed the strongest umami taste, consistent with the highest contents of Asp (25.1 mg/100 g) and Glu (67.8 mg/100 g). The addition of LAB decreased the relative contents of aliphatic aldehydes, (Z)-3-hexen-1-ol, and 1-octen-3-ol, reducing the earthy and fishy notes. However, LAB enhanced the contents of terpenoids, acids, esters, and S-containing compounds, increasing the sour, pleasant, and unique odors of Zhayu.

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The warmed-over flavor (WOF) in surimi gels was characterized by gas chromatography-ion mobility spectrometry, aroma extract dilution analysis, aroma recombination, and omission studies. Surimi gels with different WOF levels were prepared by different gelling temperatures, and surimi gels heated at 90, 100, and 121 °C were considered as the samples with light, strong, and medium WOF, respectively. Based on the quantification and odor activity values, 14 aldehydes, 2 ketones, 3 alcohols, 2 benzene-containing compounds, 2 N-containing compounds, 3 S-containing compounds, 3 lactones, undecanoic acid, and 4-methylphenol were recombined to build a spiked model for surimi gels with the strongest WOF, which showed the highest similarity with the original sample. Finally, a triangle test involving omission of the aroma compounds from the spiked model proved that the WOF in surimi gels was attributed to (E,E)-2,4-decadienal, heptanal, octanal, nonanal, decanal, (E)-2-nonenal, (E)-2-octenal, (E)-2-decenal, (E,E)-2,4-heptadienal, 2,3-pentanedione, 2,6-dimethylpyrazine, 2-propylpyridine, benzothiazole, 2-methoxybenzenethiol, and 2-furfurylthiol.

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This study investigated the effects of different reheating methods (microwave, water boiling, steaming, and frying) on the flavor of surimi gels with untreated sample as control. Electronic nose and electronic tongue results showed that microwave could better maintain the original odor and taste characteristics of surimi gels. Additionally, 43 kinds of volatile aroma compounds were detected in surimi gels, including aldehydes, alcohols, ketones, heterocycles, and esters. The aroma fingerprints of surimi gels were similar between water boiling and steaming and between microwave and the control, whereas frying showed the most unique aroma profile possibly related to the highest TBARS values. The total contents of nucleotides, carnosine and lactic acid were significantly higher in fried samples relative to other samples. In conclusion, all the reheating treatments can alter the flavor of samples, but microwave showed better performance in sensory evaluation and maintaining the original flavor of surimi gels.

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This study aimed to investigate the formation of odor properties in surimi products by exploring changes in aroma compounds and their precursors at setting (40 °C) and gelling (90 °C) stages during surimi gel formation by solvent-assisted flavor evaporation, gas chromatography-mass spectrometry, and ultra performance liquid chromatography. Results revealed a gradual increase in the contents of most aldehydes, alcohols, and phenolics during surimi gel formation, while a decrease in the contents of (E)-2-pentenal, (E)-2-hexnenal, (Z)-4-heptenal, (E)-2-heptenal, and most ketones at gelling stage. During thermal process, 50 % decrease was observed in the contents of some unsaturated fatty acids (palmitoleic acid, oleic acid, etc.), and the contents of tyrosine, phenylalanine, methionine, isoleucine, and leucine decreased significantly (P < 0.05) at gelling stage. Moreover, lipoxygenase activity reached 4.19-4.81 U/min·g at setting stage. Overall, amino acid degradation and lipid auto-oxidation mainly occurred at gelling stage to promote the formation of related compounds.

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Transglutaminase-induced cross-linking has been suggested as a strategy to govern surimi gels' texture. To achieve the aroma regulation of surimi gels by cross-links, surimi gels were treated with microbial transglutaminase to get different cross-linking degrees, and in vivo and in vitro aroma releases were investigated by a proton transfer reaction-mass spectrometry (PTR-MS). Seventeen compounds in surimi gels were detected by PTR-MS. The in vitro release curves of odorants were fitted by a pseudo-first-order kinetics model. As the cross-links increased, most aroma compounds' released concentrations and release rates decreased first, and then increased significantly (P < 0.05) when the cross-linking degree exceed around 35.4%, negatively related to the springiness and the gel strength of surimi gels. However, the in vivo aroma release results showed that the harder surimi gel released fewer aroma compounds. In conclusion, texture affected by cross-links could be a strategy to control the aroma release of surimi gels.

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Aroma-active compounds in northern highbush blueberries "Bluecrop" (Vaccinium corymbosum "Bluecrop") and "Elliott" (Vaccinium corymbosum "Elliott") were isolated using solvent extraction followed by solvent-assisted flavor evaporation. The aroma-active compounds were compared by aroma extract dilution analysis (AEDA) on a polar and a chiral column and odor activity values (OAVs). The results showed that both cultivars had similar aroma-active compounds, but the flavor dilution (FD) factors and OAV values varied, responsible for the subtle aroma differences. AEDA (FD ≥ 64) suggested that the important aroma-active compounds in both cultivars could be ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, (Z)-3-hexenal, 1-octen-3-one, (Z)-3-hexen-1-ol, methional, linalool, (E,Z)-2,6-nonadienal, 2-methylbutanoic acid, α-terpineol, (E,E)-2,4-nonadienal, ß-damascenone, geraniol, geranyl acetone, o-cresol, eugenol, and vanillin. Different isomers can have different sensory thresholds and attributes. Enantiomer analysis revealed that although S-(+)-linalool was dominant in blueberry, R-(-)-linalool had a higher FD value and OAVs than that of the (S)-isomer. The S-(-)-α-terpineol was slightly elevated than R-(+)-α-terpineol in both cultivars.

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BACKGROUND: The transglutaminase-induced cross-linking reaction can enhance the textural properties of surimi gels. However, when the cross-linking degree exceeds a certain range, surimi gels become brittle, giving the gel a special mouthfeel. Little information is to be found regarding the brittleness of surimi gel and its formation mechanism. The present study aimed to investigate the effects of cross-links on physicochemical properties of surimi gel and to analyze the reason for the textural variation of surimi gels regulated by cross-links. RESULTS: When the cross-linking degree was lower than about 30%, the surimi gel could not be fractured and the surimi gel was mushy. When the cross-linking degree was around 40-55%, surimi gels without microbial transglutaminase (MTGase) presented an elastic texture, while surimi gels with MTGase displayed a tough texture. When the cross-linking degrees were 64.1% and 76.5%, surimi gels became brittle. Water holding capacity decreased with the increase in cross-linking degree and the cross-links released some combined water to free water. With the increase in cross-links, the pore equivalent diameter and the fractal dimension first decreased and then increased. When the cross-linking degree exceeded approximately 50%, hydrophobic interaction increased, consistent with the exposure of hydrophobic residues and the decrease in the water gap between proteins. CONCLUSION: The changes in gel texture were related to micro-network structure, water status and microenvironment of proteins. It was demonstrated that the texture of slowly heated surimi-based products could be regulated by controlling the TGase-induced cross-links. © 2021 Society of Chemical Industry.

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Aroma compounds in three surimi samples, made from freshwater silver carp (Hypophthalmichthys molitrix) and saltwater Pacific whiting (Merluccius productus) and Alaska pollock (Theragra chalcogramma), were characterized by aroma extract dilution analysis, odor activity value, and odor recombination study. Results demonstrated that the most potent aroma-active compounds in the surimi were hexanal, (Z)-4-heptenal, (Z)-4-decenal, (E,Z)-2,6-nonadienal, (E,E)-2,4-nonadienal, (E,Z)-2,4-decadienal, (E,E)-2,4-decadienal, (E,E,Z)-2,4,6-nonatrienal, (E,Z,Z)-2,4,7-tridecatrienal, and (E)-4,5-epoxy-(E)-2-decenal, contributing fishy, green, oily, or metallic odors. The other aroma contributors in surimi were 1-octen-3-one, 1-octen-3-ol, dimethyl disulfide, dimethyl trisulfide, and methional. 2-Acetyl-1-pyrroline, giving a typical popcorn note, could also be an important aroma contributor as a result of the high flavor dilution factor. Pacific whiting and Alaska pollock surimi samples both had higher levels of dimethyl trisulfide and methional, whereas the silver carp surimi sample had more (E,Z)-2,4-decadienal. In general, the silver carp surimi sample had more aldehydes contributing stronger "river water, fishy" and "grassy, green" aromas. In contrast, saltwater surimi showed stronger "sea breeze-like" and "sulfur-like" odors.

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Qingke liquor is a very famous Tibetan alcoholic beverage made from "Qingke", hull-less highland barley, which is exclusively grown in Qinghai-Tibetan Plateau with an average altitude of 4000 m. Qingke liquor made in such an area whose quality or characteristics is a result of its geographic environment, including natural and human culture. In this study, the aroma compounds in two Qingke liquors made from highland barley grown at different elevations (QKH, high elevation, and QKL, low elevation) were compared by aroma extract dilution analysis (AEDA), aroma intensity (Osme), odor activity values (OAVs, ratio of concentration to odor threshold), and aroma recombination. Results revealed ethyl acetate, ethyl 2-methyl propanoate, ethyl butanoate, ethyl 3-methyl butanoate, ethyl pentanoate, ethyl hexanoate, ethyl octanoate, 3-methylbutanal, 3-methyl-1-butanol, 1-octen-3-ol, ß-damascenone, 2,3-butanedione (diacetyl), acetoin, and 2-methoxyphenol (OAV ≥ 10) as important aroma active compounds to Qingke liquors. However, QKH had higher OAVs for most of the compounds than that of QKL. An aroma recombination study confirmed the analysis of aroma-active compounds in Qingke liquor, whereas the aroma emission test demonstrated 3-methylbutanal as the key aroma compound for both Qingke liquors.

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BACKGROUND: Ultrasound and Ca2+ have been used separately to increase myosin properties in fish processing. However, little is know about how myosin changes are affected by Ca2+ and ultrasound in combination. The present study aimed to investigate the effects of the ultrasound-calcium combination system on aggregation and conformational changes of silver carp myosin. RESULTS: Ultrasound facilitated a Ca2+ -induced increase in turbidity. As the Ca2+ concentration increased from 0 to 100 mmol L-1 , there was an obvious increase in the turbidity, solubility and mean hydrated particle size of myosin after ultrasound treatment compared to without treatment. Moreover, changes of total and reactive SH contents depended on the ultrasound-calcium combination conditions. Under this combination system, myosin surface hydrophobicity significantly increased for the synergistic effect of ultrasound and Ca2+ . Furthermore, the ultrasound-calcium combination conditions could affect myosin gelation, with better gelation properties being observed for myosin treated with a combination of 60 mmol L-1 Ca2+ and 9 min of ultrasound. CONCLUSION: The combination system reported in the present study was beneficial for myosin unfolding, facilitating intermolecular interactions between Ca2+ and myosin. Ultrasound treatment promoted myosin aggregation via the induction of Ca2+ and reduced the critical concentration of Ca2+ required to aggregate myosin. In the fish processing industry, this combination system can enhance the gelation properties of surimi-based products. © 2018 Society of Chemical Industry.

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To enhance the application of transglutaminase (TGase) in processing and preserving of frozen surimi, the mechanism that enhances surimi gelation induced by TGase after short-term freezing was investigated. Gel properties and cross-linking extent of surimi gels increased when surimi was frozen at -18 °C for 5-7 days. However when storage time exceeded 10 days, textural properties and water-holding capacity decreased significantly. Moreover, the difference of breaking force and hardness between surimi gels with and without TGase reached the maximum after 3-5 days of frozen storage. Free amino content of myosin increased during the first 7 days, and TGase activity increased significantly during the first 3 days. Short-term frozen storage unfolded myosin structure, decreased α-helix content, and exposed hydrophobic patches, which promoted cross-linking reactions and intermolecular hydrophobic interactions. This study provides some new ideas for the processing, storage and transport of frozen surimi and manufacture of frozen surimi-based products.

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