Effects of Alternating Electric Field Assisted Freezing-Thawing-Aging Sequence on Data-Independent Acquisition Quantitative Proteomics of Longissimus dorsi Muscle

Solubilization of fish myofibrillar proteins in NaCl and KCl solutions: A DIA-based proteomics analysis

Understanding the basic solubilization of fish myofibrillar proteins (MPs) in common monovalent chloride solutions is crucial for muscle food processing. In this study, the differential proteomic profiles of MPs during extraction and solubilization in NaCl and KCl solutions were investigated by using advanced four-dimensional data-independent acquisition (4D DIA) quantitative proteomics for the first time. Compared to routine biochemical analysis, this could provide insights into the solubilization of muscle proteins. We ensure the consistency of the effective ionic strength of NaCl and KCl buffers by adjusting the conductivity. The results showed that NaCl extractor mainly facilitated the solubilization of cytoskeletal proteins, biochemical enzymes, and stromal proteins compared to KCl, such as tubulin, myosin-9, collagen, plectin, protein phosphatase, and cathepsin D. However, no significant difference was observed in the extraction of major sarcomeric proteins, including myosin, actin, troponin C, myosin-binding protein C, M-Protein, α-actinin-3, and tropomyosin.

To What Extent Do Low-Voltage Electrostatic Fields Play a Role in the Physicochemical Properties of Pork during Freezing and Storage?

Low-voltage electrostatic fields (LVEF) are recognized as a new technology that can improve the quality of frozen meat. To determine the extent to which LVEF assistance affects the quality of frozen pork for long-term storage, pork was frozen and stored at -18 and -38 °C for up to 5 months. Water-holding capacity, muscle microstructure, and protein properties were investigated after up to 5 months of frozen storage with and without LVEF assistance. In comparison to traditional -18 and -38 °C frozen storage, LVEF treatment inhibited water migration during frozen storage and thawing. As a result, thawing losses were reduced by 15.97% (-18 °C) and 3.38% (-38 °C) in LVEF-assisted compared to conventional freezing methods. LVEF helped to maintain the muscle fiber microstructure and reduce muscle protein denaturation by miniaturizing ice crystal formation by freezing. As a result of this study, LVEF is more suitable for freezing or short-term frozen storage, while a lower temperature plays a more significant role in long-term frozen storage.

Postmortem Muscle Proteome Characteristics of Silver Carp (Hypophthalmichthys molitrix): Insights from Full-Length Transcriptome and Deep 4D Label-Free Proteomic

The coverage of the protein database directly determines the results of shotgun proteomics. In this study, PacBio single-molecule real-time sequencing technology was performed on postmortem silver carp muscle transcripts. A total of 42.43 Gb clean data, 35,834 nonredundant transcripts, and 15,413 unigenes were obtained. In total, 99.32% of the unigenes were successfully annotated and assigned specific functions. PacBio long-read isoform sequencing (Iso-Seq) analysis can provide more accurate protein information with a higher proportion of complete coding sequences and longer lengths. Subsequently, 2671 proteins were identified in deep 4D proteomics informed by a full-length transcriptomics technique, which has been shown to improve the identification of low-abundance muscle proteins and potential protein isoforms. The feature of the sarcomeric protein profile and information on more than 30 major proteins in the white dorsal muscle of silver carp were reported here for the first time. Overall, this study provides valuable transcriptome data resources and the comprehensive muscle protein information detected to date for further study into the processing characteristic of early postmortem fish muscle, as well as a spectral library for data-independent acquisition and data processing. This batch of muscle-specific dependent acquisition data is available via PRIDE with identifier PXD043702.

Proteomic Comparisons of Caprine Milk Whole Cream Buttermilk Whey and Cheese Whey Cream Buttermilk

Buttermilk, a potential material used to produce milk fat globule membrane (MFGM), is obtained as a byproduct of butter making from milk whole cream and cheese whey cream. This study investigated the effects of rennet and acid coagulation on the protein profiles of buttermilk rennet-coagulated whey (BRW) and buttermilk acid-coagulated whey (BAW). They were compared to those of whey cream buttermilk (WCB). Rennet coagulation was more efficient in removing casein, while retaining more IgG and lactoferrin than acid coagulation. BRW had more MFGM than BAW. Butyrophilin, xanthine dehydrogenase, and mucin1 were significantly higher (P < 0.05) in BRW, while fatty acid-binding protein 3 was enriched in BAW. KEGG analysis showed that complement and coagulation cascades had the greatest differences, and the abundance of proteins involved in this signaling pathway in BRW and BAW was higher, suggesting their potential anticoagulant and anti-inflammatory activity. BAW had higher apolipoprotein A4 and transcobalamin 2, which are essential carriers for transporting long-chain fatty acids and vitamin B12 from the intestine to the blood. Therefore, BAW intake might improve lipids and vitamin B12 absorption. This study can help deepen the understanding of protein composition of MFGM-enriched whey and facilitate the production of MFGM proteins for infants and old-aged populations.

Effects of alternating electric field assisted freezing-thawing-aging sequence on longissimus dorsi muscle microstructure and protein characteristics

The current study investigates the influence of alternating electric field (AEF)-assisted freezing-thawing-aging sequence on the muscle microstructure and myofibrillar protein characteristics. Three treatments were used for longissimus dorsi (LD) muscle: only aging (OA), freezing-thawing-aging sequence (FA) and AEF-assisted freezing-thawing-aging sequence (EA). Compared with the FA and EA groups, the OA group showed considerably fewer cracks between muscle fibers and maintained the integrity of the Z-line as observed using scanning and transmission electron microscopy, respectively. Furthermore, the EA treatment effectively decreased myofibrillar fragmentation, myofibrillar protein aggregation, and protein oxidation, as shown by the myofibrillar fragmentation index, turbidity, and total sulfhydryl concentration. Analysis of surface hydrophobicity and the Fourier transform infrared, UV absorption, and fluorescence spectrums indicated that AEF minimized the alterations of protein secondary and tertiary structure alterations during aging after freezing.

Effects of alternating electric field during freezing and thawing on beef quality

Alternating electric field (AEF) technology was used during freezing-thawing-aging (FA) of beef aged for 0, 1, 3, 5 and 7 days. Color, lipid oxidation, purge loss, cooking loss, tenderness, and T₂ relaxation time were determined for frozen-thawed-aged beef with AEF (AEF + FA) or without AEF (FA) and compared to aged only (OA) controls. FA increased purge loss, cooking loss, shear force values and lipid oxidation (P < 0.05) but decreased a* values compared with AEF + FA treatment. It also exacerbated the spaces between muscle fibers and contributed to the transformation of immobile water to free water. AEF served to maintain meat quality by reducing purge loss, cooking loss and increasing meat tenderness and maintaining color and lipid oxidation only in steak that was frozen before aging. This most likely occurred due to AEF increasing the speed of freezing and thawing and by reducing the space between muscle fibers compared to FA alone.