Orthogonality of non-coaxial Laguerre-Gaussian beams.

The conventional orthogonality of Laguerre-Gaussian (LG) beams is widely recognized and serves as the fundamental basis for mode division multiplexing utilizing LG beams as channels. However, this conventional orthogonality holds true only when two LG beams share the same axis. Whether non-coaxial LG beams, with parallel axes separated by a distance, are orthogonal to each other remains an open question. To address this issue and reveal the orthogonality of non-coaxial LG beams, we analytically derive the projection of one LG beam onto another. This projection exhibits a helical phase and a rotationally symmetric amplitude with dark rings present. These dark rings indicate that two non-coaxial LG beams are indeed orthogonal to each other when their axes are appropriately separated. Furthermore, any pair of non-coaxial LG beams within a set also exhibit orthogonality when their axes are fixed at a certain separation distance. This novel form of orthogonality predicts an innovative compound multiplexing technique that simultaneously combines mode and space, enabling more efficient packing of multiple LG beams within a single transmission aperture while maintaining parallel and closely spaced beam axes.

Characterization of the effect of different cooking methods on volatile compounds in fish cakes using a combination of GC-MS and GC-IMS.

In this study, gas chromatography-mass spectrometry (GC-MS) and gas chromatography-ion mobility spectrometry (GC-IMS) were used to analyze the volatiles of fish cakes obtained using five cooking methods, namely, steaming, baking, air frying, pan frying and deep frying. The odor activity value (OAV) and relative odor activity value (ROAV) were used to screen for the major aroma compounds. Orthogonal partial least squares discriminant analysis (OPLS-DA) and the variable influence on projection (VIP) were used to determine the characteristic flavor compounds in the fish cakes. A total of 72 volatile compounds were identified by GC-MS, and 41 volatile compounds were detected by GC-IMS. 3-ethyl-2,5-dimethylpyrazine and 2,5-dimethylpyrazine were not detected in either CK or SS. The OPLS-DA models for GC-MS and GC-IMS analyses were constructed based on VIP values, and 8 and 7 compounds, respectively, were screened as characteristic aroma compounds. The results of this study provide new insights into the dynamics of flavor formation in reheated fish cakes and provide a theoretical basis for the optimization of the production process of this food product.

GC-MS, GC-IMS, and E-Nose Analysis of Volatile Aroma Compounds in Wet-Marinated Fermented Golden Pomfret Prepared Using Different Cooking Methods.

The cooking method is extremely important for the production of low-salt, wet-marinated, fermented golden pomfret because it strongly influences its flavor components and organoleptic quality. There are also significant differences in flavor preferences in different populations. The present study analyzed differences in the aroma characteristics of wet-marinated fermented golden pomfret after boiling, steaming, microwaving, air-frying, and baking using a combination of an electronic nose, GC-IMS, and SPME-GC-MS. Electronic nose PCA showed that the flavors of the boiled (A), steamed (B), and microwaved (C) treatment groups were similar, and the flavors of the baking (D) and air-frying (E) groups were similar. A total of 72 flavor compounds were detected in the GC-IMS analysis, and the comparative analysis of the cooked wet-marinated and fermented golden pomfret yielded a greater abundance of flavor compounds. SPME-GC-MS analysis detected 108 flavor compounds, and the results were similar for baking and air-frying. Twelve key flavor substances, including hexanal, isovaleraldehyde, and (E)-2-dodecenal, were identified by orthogonal partial least-squares discriminant analysis (OPLS-DA) and VIP analysis. These results showed that the cooking method could be a key factor in the flavor distribution of wet-marinated fermented golden pomfret, and consumers can choose the appropriate cooking method accordingly. The results can provide theoretical guidance for the more effective processing of fish products and the development of subsequent food products.

The Cryoprotective Effect of an Antifreeze Collagen Peptide Complex Obtained by Enzymatic Glycosylation on Tilapia.

Antifreeze peptides have become effective antifreeze agents for frozen products, but their low quantity of active ingredients and high cost limit large-scale application. This study used the glycosylation of fish collagen peptides with glucosamine hydrochloride catalyzed by transglutaminase to obtain a transglutaminase-catalyzed glycosylation product (TGP) and investigate its antifreeze effect on tilapia. Compared with the blank group, the freshness (pH value of 6.31, TVB-N value of 21.7 mg/100 g, whiteness of 46.28), textural properties (especially hardness and elasticity), and rheological properties of the TGP groups were significantly improved. In addition, the protein structures of the samples were investigated using UV absorption and fluorescence spectroscopy. The results showed that the tertiary structure of the TGP groups changed to form a dense polymer. Therefore, this approach can reduce the denaturation and decomposition of muscle fibers and proteins in fish meat more effectively and has a better protective effect on muscle structure and protein aggregation, improving the stability of fish meat. This study reveals an innovative method for generating antifreeze peptides by enzymatic glycosylation, and glycosylated fish collagen peptide products can be used as new and effective green antifreeze agents in frozen foods.

Changes in protein and volatile flavor compounds of low-salt wet-marinated fermented Golden Pomfret during processing.

In this experiment, the changes in protein hydrolysis, protein oxidation, and flavor of low-salt wet-marinated fermented golden pomfret were studied during processing. During processing, a decrease in sulfhydryl content (P < 0.05), a significant increase in protein surface hydrophobicity (P < 0.05), a significant increase in carbonyl content and TCA-soluble peptide (P < 0.05), an increase in TVB-N and amino acid nitrogen (P < 0.05), and a significant increase in the content of free amino acids (P < 0.05), indicating that proteins were gradually oxidized and degraded to small molecules and flavor precursors under the action of bacterial reduction pretreatment, deodorization, marination and fermentation processes, small molecules and aroma precursors was generated by gradual oxidative decomposition. In the course of processing, a total of 113 volatile flavor compounds were identified using GC-MS analysis, while OPLS-DA analysis and VIP value determination led to the identification of 10 characteristic flavor compounds. The results showed that an abundance of flavor compounds was generated during the processing, thereby imparting a more pronounced taste profile to the low-salt wet-marinated fermented golden carp. The results showed that a large number of flavor substances were generated during the processing to give a richer flavor to low-salt wet-marinated fermented golden pomfret that could provide data and theoretical support for the subsequent processing industry of golden pomfret.