Effects of high-voltage electrostatic field (HVEF) on frozen shrimp (Solenocera melantho) based on UPLC-MS untargeted metabolism

Highlights

• HVEF treatment improved the quality of frozen shrimp meat.

• 367 metabolites were identified in HVEF group, and 108 metabolites had KEGG ID.

• Purine metabolism and pyrimidine metabolism were the most enriched pathways.

• PCs, HxR and l-valine were important metabolites of shrimp during storage.

Abstract

Shrimp meat is prone to autolysis and decay due to the abundance of endogenous enzymes and contamination from microorganisms. HVEF freezing can slow the spoilage of shrimp, producing small and uniform ice crystals, resulting in less damage to muscle tissue. In this study, HVEF technique was used to freeze the shrimp (Solenocera melantho), and the UPLC-MS metabolic technique was used to investigate the metabolites of frozen shrimp meat. Compared with the control group, 367 differential metabolites were identified in the HVEF group. Mapping them to the KEGG database, there were 108 with KEGG ID. Purine metabolism and pyrimidine metabolism were the most enriched pathways. In addition, phosphatidylcholines (PCs), inosine (HxR), and l-valine were identified as potential biomarkers associated with lipid, nucleotide, and organic acid metabolism, respectively. Overall, HVEF can improve freezing quality of shrimp meat by slowing down the metabolism of substances in the muscle of S. melantho.

Introduction

As an important economic species in China, Solenocera melantho is rich in nutrients, especially high-quality proteins (Carrion-Granda, Fernandez-Pan, Jaime, Rovira, & Mate, 2016). Due to abundant endogenous enzymes and microbial contamination, aquatic products are perishable after harvesting and undergo various changes such as rigor mortis, autolysis, and spoilage (Ghaly, 2010, Gram, 2009). In this process, various major components (e.g., proteins and lipids) break down to produce new substances, which leads to changes in texture, flavor, and nutrition. Hence, freezing immediately after harvest is commonly used to reduce the damage to shrimp quality (Fennema, Karel, & Lund, 1975), while important chemical or enzymatic autolysis reactions still occur (Boonsumrej et al., 2007, Okpala, 2016). The muscle fibers of shrimp meat are also destroyed during the freezing process, and the taste becomes unpleasant and nutrients are lost.

Electrostatic field technology has received extensive attention in the food industry, especially in food preservation and quality control of frozen products (Dalvi-Isfahan, Hamdami, Le-Bail, & Xanthakis, 2016). HVEF is used to thaw frozen meat products (such as pork, chicken, and fish), improving their protein content and texture (Jia et al., 2018, Mousakhani-Ganjeh et al., 2015, Rahbari et al., 2018). HVEF can produce small and uniform ice crystals, resulting in less damage to muscle tissue (Liu et al., 2022). The nutrition and flavor of meat are related to small molecular compounds, such as lipids, carbohydrates, amino acids, nucleotides, and organic acids. The electric field kills bacteria (Sale, 1967), and the metabolic reaction of microorganisms changes, which affects the nutrition and flavor of food (Johanningsmeier, Harris, & Klevorn, 2016). Metabolomics based on mass spectrometry (MS) has been gradually applied to food composition analysis and food control (Wishart, 2008). There have been several studies regarding the metabolomics of meat products. Still, few have paid attention to the differences in the frozen quality of meat using metabolomics technology after HVEF treatment. Metabolomics based on nuclear magnetic resonance (NMR), gas chromatography-mass spectroscopy (GC–MS), and liquid chromatography-mass spectroscopy (LC-MS) can all be used for metabolite detection. Among them, LC-MS has the advantages of high throughput, resolution, and sensitivity, and is ideal for analyzing metabolites that are difficult to volatilize or have low thermal stability. (Vinaixa, Schymanski, Neumann, Navarro, Salek, & Yanes, 2016). LC-MS can also identify organic acids, nucleotides, and other small molecule metabolites when compared to GC–MS.

In this study, HVEF with a strength of 15 kV/m was used to assist in freezing shrimp (S. melantho), and shrimp frozen without an electric field were set as a control group. UPLC-MS technology was utilized to analyze differential metabolites in the two groups of samples, and the effects of HVEF on shrimp nutrition and flavor were compared. This study provides a molecular understanding of the metabolic mechanisms involved in HVEF during shrimp freezing and provides a possibility for applying HVEF in freezing other aquatic products.