Effects of Inoculation with Koji and Strain Exiguobacterium profundum FELA1 on the Taste, Flavor, and Bacterial Community of Rapidly Fermented Shrimp Paste.

This study was conducted to investigate the effect of inoculation with Exiguobacterium profundum FELA1 isolated from traditional shrimp paste and koji on the taste, flavor characteristics, and bacterial community of rapidly fermented shrimp paste. E-nose and e-tongue results showed higher levels of alcohols, aldehydes, and ketones, enhanced umami and richness, and reduced bitterness and astringency in samples of shrimp paste inoculated with fermentation (p < 0.05). Eighty-two volatile compounds were determined using headspace solid-phase microextraction and gas chromatography-mass spectrometry (HS-SPEM-GC-MS). The contents of 3-methyl-1-butanol, phenylethanol, isovaleraldehyde, and 2-nonanone in the inoculated samples were significantly increased (p < 0.05), resulting in pleasant odors such as almond, floral, and fruity. High-throughput sequencing results showed that the addition of koji and FELA1 changed the composition and abundance of bacteria and reduced the abundance of harmful bacteria. Spearman's correlation coefficient indicated that the alcohols, aldehydes, and ketones of the inoculated fermented samples showed a strong correlation (|ρ| > 0.6) with Virgibacillus and Exiguobacterium, which contributed to the formation of good flavor in the fast fermented shrimp paste. This study may offer new insights into the production of rapidly fermented shrimp paste with better taste and flavor.

Insight into the correlations among rheological behaviour, protein molecular structure and 3D printability during the processing of surimi from golden pompano (Trachinotus ovatus).

To investigate the 3D printability of surimi from golden pompano, the rheological properties, protein molecular structure, and 3D printability of food inks from every step of surimi processing were measured, and their correlations were analysed. The results showed that surimi from chopping (surimi-C), chopping with salt (surimi-CS) and setting (surimi-S) were suitable for 3D printing, among which surimi-CS had the best shape fidelity. The clustering analysis of variables revealed that the yield stress and AF could be used as indexes to characterize extrusion and deposition behaviour of surimi, respectively. The accuracy of 3D printing was affected by the extrusion property of the food ink, which was controlled by the ionic bond content. The stability of 3D printing was affected by the self-supporting capacity of the food ink, which was controlled by the hydrogen bond and hydrophobic interaction contents. The results provided theoretical guidance for developing 3D printing of surimi ingredients.

LF-NMR as a tool for predicting the 3D printability of surimi-starch systems.

In this study, surimi from golden pompanos was mixed with starch to form a surimi-starch system. The water properties, rheological properties, and three-dimensional (3D) printability of the surimi-starch were measured. Cluster analysis results showed that the 3D printability was closely related to the type and addition content of starch, and the water and rheological properties. The low-field nuclear magnetic resonance (LF-NMR) parameters were used to predict 3D printability using polynomial regression models. The correlation coefficients (R2) for 3D printing accuracy and stability were 0.88 and 0.93, and the root mean square error (RMSE) values were 0.20% and 4.59%, respectively. In the verification test, the R2 for the two models were 0.85 and 0.89, and the RMSE values were 0.20% and 1.06%, respectively. The nonlinear surface regression fitting exhibited superior predictive performance. Therefore, LF-NMR is a good non-destructive tool for quickly and accurately predicting the 3D printability of the surimi-starch systems.

Insight into muscle quality of golden pompano (Trachinotus ovatus) frozen with liquid nitrogen at different temperatures.

The effects of different liquid nitrogen freezing (LNF) temperatures (-35, -55, -75, -95, and -115 °C) on the freezing rate, physicochemical properties, and microstructure of golden pompano (Trachinotus ovatus) were evaluated in the present study. The results showed that the total freezing time of golden pompano was significantly shortened using LNF (P < 0.05). Compared with other freezing methods, the cooking loss and L* values (lightness) of -95 °C LNF golden pompano were significantly lower, the false-colour image was much redder and brighter, the loss and mobility of water in fish muscle were inhibited, the water holding capacity and hardness were higher, and the muscle microstructure was comparatively intact. Therefore, -95 °C LNF effectively shortened the freezing time and improved the muscle qualities of frozen golden pompano.

The relationship between rheological and textural properties of shrimp surimi adding starch and 3D printability based on principal component analysis.

The three-dimensional (3D) printing properties of pure shrimp surimi are poor and require improvement via the addition of other materials. The effects of the different amounts of potato starch, corn starch, tapioca starch, and cross-linked starch (CLS) (0%, 3%, 6%, or 9%, respectively) on the 3D printing properties and material properties of white shrimp (Litopenaeus vannamei) surimi were evaluated in the present study. The results showed that the apparent viscosity, G', and G'' of the samples were increased by adding 6% CLS, making it easy to extrude the sample from the nozzle and resulting in an improvement in the printing accuracy. In addition, after adding 6% CLS, the hardness, adhesiveness, and springiness of the sample were increased, which assist with maintaining the shape of the printed material and improve the printing stability of the sample. Moreover, the water holding capacity of shrimp surimi increased as a result of the addition of 6% CLS. In summary, 6% CLS can improve the material properties of shrimp surimi and make it more suitable for 3D printing.

Investigation on the correlation between changes in water and texture properties during the processing of surimi from golden pompano (Trachinotus ovatus).

Water and texture properties are important indicators for evaluating surimi and surimi seafood quality. The present study assessed the impact of surimi processing on the water and texture properties and analyzed their correlations. The results showed that the moisture content exhibited significant positive correlations with T22 and A22 (P < 0.05). However, water-holding capacity (WHC) revealed significant negative correlation with T21 and A22 (P < 0.05). Moreover, correlations between water and texture properties were observed. Moisture content and A22 displayed significant negative correlation with hardness (P < 0.05). WHC exhibited significant positive correlations with cohesiveness, springiness, and chewiness (P < 0.05), whereas T21 exhibited significant negative correlation with those properties (P < 0.05). Springiness is an important indicator for texture properties of surimi gel. T21 and WHC exhibited significant correlations with springiness (P < 0.05). We used two equations to assess the relationship between springiness and T21 (y = 9.64 × x2 - 33.79 × x + 29.62, R2 = 0.995, P < 0.05) and between springiness and WHC (y = 0.57 + 9.05/{1+e[-29.29 × ( x - 83.90)] }0.01 , R2 = 0.999, P < 0.05), respectively. Verification experiments proved that these two regression equations could be used to predict the change law among feature indicators during the processing of surimi seafood. The present study finds an easy-to-control method to monitor the quality of surimi production and processing for all the stages, and provides ideas for quality design of surimi products. PRACTICAL APPLICATION: The quality of surimi seafood is affected by the process used for surimi production. Early detection of the material quality can efficiently prevent resource wastage. The feature indicators and their correlations help in easy-to-control of all surimi processing stages. Low-field nuclear magnetic resonance (LF-NMR) is a fast, nondestructive method for monitoring food real-time, but the instrument is expensive; whereas water-holding capacity and texture profile analysis (TPA) are traditional methods but time-consuming and material-consuming. Surimi enterprises or researchers choose the right methods based on their needs.

Characterization and comparison of collagen extracted from the skin of the Nile tilapia by fermentation and chemical pretreatment.

Chemical pretreatment of collagen raw materials is time-consuming and environmentally hazardous. Collagen extraction after fermentation pretreatment has not been reported. We extracted and characterized acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) from Nile tilapia (Oreochromis niloticus) skin following fermentation and chemical treatments and comparatively evaluated the feasibility of fermentation. Fermentation-ASC (FASC) and fermentation-PSC (FPSC) yields (4.76 and 8.14 wt%, respectively) were slightly but not significantly higher than chemical-ASC (CASC) and chemical-PSC (CPSC) yields (4.27 and 7.60 wt%, respectively). All extracts were identified as type I collagens by SDS-PAGE and retained their triple helical structure well, as confirmed through Fourier transform infrared spectroscopy. All collagen microstructures under scanning electron microscopy were multi-layered aggregates. These collagens also had similar biochemical properties (i.e. denatured between 36.5 and 37.1 °C, high soluble at pH 1-4 and at <3% [w/v] NaCl). Therefore, fermentation method is a viable alternative for pretreating collagen extraction materials.