The effect and mechanism of four drying methods on the quality of tilapia fillet products

Effect of non-enzymatic browning on oysters during hot air drying process: Color and chemical changes and insights into mechanisms

Hot air drying (HAD) is an extensive method used on oysters and it causes the most intuitive change, a color change. However, the mechanism of color change remains unclear. This study showed that oysters underwent browning during the HAD process. The colorimetric parameter L* decreased while a* and b* increased, all of which were well described by the first-order color kinetic model. Mechanistically, the HDA process induced the oxidative browning of phenols and the generation of Maillard reaction products (5-hydroxymethylfurfural and hydrophilic pyrrole). Meanwhile, the HAD process caused lipid oxidation, leading to the reduction of phosphatidylethanolamine and the generation of reactive carbonyl compounds (aldehydes and α-dicarbonyl compounds). Moreover, the accumulation of hydrophobic pyrroles, a lipid-induced Maillard-like reaction product, was observed. These results suggest that, in addition to phenolic oxidation, sugar- and amino acid-mediated non-enzymatic browning reactions, lipid-mediated Maillard-like reactions play important roles in oyster darkening during the HAD process.

Investigation on 3D printing of shrimp surimi under different printing parameters and thermal processing conditions

Improving the printing accuracy and stability of shrimp surimi and finding appropriate printing parameters and suitable thermal processing method can help to develop high value-added 3D printing products of shrimp surimi. It was found that in order to make the 3D printing products of shrimp surimi have higher printing adaptability (printing accuracy and printing stability reach more than 97%), by choosing nozzle diameter of 1.20 mm and setting the printing height of the nozzle to 2.00 mm, the layers of the printed products were better fused with each other, and the printing accuracy of the products could be greatly improved; there was no uneven discharge and filament breakage when the nozzle moved at the speed of 30 mm/s; and the products were internally compact and had good stability when the printing filling rate was 80%. In addition, the deformation rates of steamed, boiled and deep-fried shrimp surimi products were significantly higher than those of oven-baked and microwaved shrimp surimi products (P < 0.05). Microwave heating had a greater effect on the deformation and color of shrimp surimi products, and was not favored by the evaluators. In terms of deformation rate, sensory score, and textural characteristic, the oven-baked thermal processing method was selected to obtain higher sensory evaluation scores and lower deformation rates of shrimp surimi 3D printed products. In the future, DIY design can be carried out in 3D printing products of shrimp surimi to meet the needs of different groups of people for modern food.

Effects of thermal and salt water soaking pre-treatment on the physicochemical and nutritional properties of sundried tilapia fish (Oreocromis niloticus) products

The effects of saltwater soaking (10-30 %, w/v) and thermal (60°C-90 °C) pre-treatment on the physicochemical and nutritional quality of sundried tilapia fish (Oreocromis niloticus) products were assessed. The wet reduction was 14.47 % in the sample treated with a 30 % salt solution at 90 °C, whereas the wet reduction of 21.23 % was observed in the sample without treatment (control). Protein, lipid, and ash content were increased significantly (P < 0.05) with higher pre-treatment salt concentration and temperature, while the moisture content showed the opposite trend. The content of essential and non-essential amino acids in the treated samples ranged from 7149.97 mg/100 g to 8063.42 mg/100 g and 10530.66 mg/100 g to 11365.59 mg/100 g, respectively, whereas the values were 7018.55 mg/100 g and 10400.84 mg/100 g, respectively in the control. The fatty acids composition, particularly ω-3 polyunsaturated fatty acids, was higher in pretreated samples (6.14-7.08 %) compared to the control. Mineral content was found to improve with saltwater and thermal pre-treatment, and the levels of heavy metals, including Ni and Cu, were significantly lower in the sundried tilapia fish. The sample pretreated with 10 % salt solution and 75 °C showed the highest rehydration capacity of 66.63 %. These findings suggest that saltwater and thermal pre-treatment can effectively enhance the physicochemical and nutritional properties of sundried tilapia fish products.

Quality improvement of tilapia fillets by light salting during repeated freezing-thawing: Contribution of structural rearrangement and molecular interactions

The present study evaluated the effects and underlying mechanisms of light salting on quality properties of tilapia fillets during repeated freezing-thawing. Light salting was found to improve water-holding capacity and decelerated texture softening in tilapia fillets during repeated freezing-thawing. Instead of tissue distortion and heterogeneous aggregates in control groups, light salting promoted myofibril disassembly and formation of an ordered protein network with the solubilized myofibrillar proteins. The myofibrils presented an overall amorphous appearance with the loss of M-lines, removing the restraints to myofibril swelling and solubilization from A-binds in salted groups during repeated freezing-thawing. The structural rearrangement caused by light salting facilitated the enlargement of water-holding space, transformation of tissue water, and tissue recoverability, improving water-holding capacity and texture properties of tilapia fillets during freezing-thawing. The finding provided novel insight into the improvement of quality properties of tilapia fillets by light salting when subjected to drastic temperature fluctuations.

Investigation of the mechanism of different 3D printing performance of starch and whole flour gels from tuber crops

This study aims to reveal the variation in 3D printing performance of whole flour and starch gels as derived from different varieties of tuber crops including cassava, potato, and yam, along with its mechanism. The whole flour of the same tuber crops showed a higher branching degree, average molecular weight (R¯_h), and the proportion of AM chains for 100 < X ≤ 1000 than its starch. Due to the higher degree of branching, the crystallinity of whole flour reached a higher level. In this circumstance, G2' of the dispersion system decreased, which facilitated smooth extrusion of ink from the nozzle, thus improving the precision of printing for the final product. Besides, a higher R¯_h and the percentage of AM chains for 100 < X ≤ 1000 made it easier for the material to extrude, thus enhancing the printing accuracy of the product. The higher short-range ordered structure of whole flour also enhanced the printing performance of 3D printed products. This research contributes an effective solution to the selection of starch and whole flour for food 3D printing.

Mesona chinensis polysaccharide accelerates the short-term retrogradation of debranched waxy corn starch

The effect of non-starch polysaccharides on the structural and functional properties of native starch have been extensively studied. However, the effect of non-starch polysaccharides on the structural characteristics of debranched starch, a kind of enzymatic modified starch, remains unclear. The aim of this study is to investigate the effects of Mesona chinensis polysaccharide (MP) on starch retrogradation and structural properties of debranched waxy corn starch (DWS). The results showed that only appropriate addition of MP (0.5 or 1%) can effectively promote the short-term retrogradation of DWS, while excessive MP (3 or 5%) had a negative effect. Gel hardness results revealed that the short-term retrogradation (24 h) of DWS could be divided into two phases. The retrogradation of DWS-MP gels mainly occurred at first stage (0–4 h), which was demonstrated by the rapid increase of gel hardness and relative crystallinity in this stage. In the second stage (4–24 h), DWS-MP gels were more likely to undergo the aggregation of starch granules as proved by SEM and particle size results. The degree of short-range ordered decreased during the total retrogradation stage. Overall, this work aims to provide an insight into the effect of non-starch polysaccharides on the short-term retrogradation of DWS.

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Only the appropriate addition of MP could accelerate the retrogradation of DWS.

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The short-term retrogradation of DWS could be divided into two stages.

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Gel hardness and relative crystallinity increased significantly in the first stage.

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The degree of short-range ordered reduced monotonically with retrogradation time.

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Starch particles mainly underwent aggregation in the second stage.