Sodium plays an important role in improving the flavor and texture as well as prolonging the shelf life of meat products. It is one of the most widely used food additives in the processing of meat products. However, excess sodium intake can increase the incidence of many diseases such as stomach cancer, osteoporosis, nephropathy, diabetes and cardio-cerebrovascular diseases. Therefore, reasonable reduction of sodium use and the application of appropriate sodium reduction technologies are essential for the field of meat processing. In this paper, the effects of sodium on the quality of meat products are reviewed and the conventional sodium reduction methods (such as directly reducing the addition of sodium, changing the physical form of sodium, using sodium substitutes, and adding flavor enhancers or quality improvers) and the novel processing technologies (such as ultrasound, ultra-high pressure, pulsed electric field and micronization) for the production of low-sodium meat products are summarized. This review is expected to provide a theoretical reference for improving the quality and processing of low-sodium meat products.

Tyramine in meat and meat products is a biogenic amine produced by some bacteria (Enterococcus faecalis and Enterococcus faecium) under favorable condition (25 ℃, pH < 7). Excessive intake of tyramine in meat products can cause hypertension, migraine and other diseases and harm human health. Therefore, inhibiting or reducing the formation of tyramine in meat and meat products has become a new research hotspot. The currently available methods of inhibiting the formation of tyramine in meat and meat products include physical, chemical and biological ones. Plant active ingredients can inhibit the formation of tyramine effectively by virtue of their bacteriostatic (antioxidant) properties, thus reducing the accumulation of tyramine in meat products. In this paper, the formation pathway of tyramine in meat and meat products, the antibacterial and antioxidant properties and structures of plant extracts, and their inhibitory effect on the formation and accumulation of tyramine are reviewed, with an emphasis on the underlying mechanism. This review is expected to provide technical support for reducing the content of biogenic amines in meat products, thus improving the safety of meat and meat products, and increasing the application of plant-derived bioactive ingredients in foods.

The effects of different periods (0, 5, 15, 25 and 35 min) of ultrasound pretreatment at a power of 200 W on the structural characteristics of sea cucumber gonad protein hydrolysates prepared with neutral protease were investigated by ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy and fluorescence spectroscopy as well as determination of surface hydrophobicity and particle size distribution and microstructure observation. The results showed that the UV absorbance, β-sheet relative content, fluorescence intensity (FI), surface hydrophobicity and particle size of sea cucumber gonad protein hydrolysates initially increased and then decreased with ultrasound pretreatment time, while the opposite trend was observed for α-helix relative content. Ultrasound pretreatment for 15 min increased the UV absorbance, β-sheet relative content, FI and surface hydrophobicity of hydrolysates by 7.30%, 50.72%, 4.50% and 13.42%, respectively, and decreased the α-helix relative content by 9.98% (P < 0.05). Moreover, this treatment resulted in the smallest particle size and distribution range of hydrolysates as observed under scanning electron microscopy (SEM). Therefore, appropriate ultrasound pretreatment could promote the unfolding of sea cucumber gonad protein structure and reduce protein aggregation, and the effect of ultrasound pretreatment for 15 min was most pronounced.

Low-temperature freezing is the oldest, most extensively and most cost-effective method of preserving meat, During freezing, frozen storage and thawing, eighty percent of the water in meat undergoes two phase transitions from water to ice to water, and ice crystals are formed and then melted, which will cause damage to muscle cells, resulting in oxidization of muscle protein and fat, a decrease in water-holding capacity, color darkening, tissue collapse and a reduction or even loss of nutritional value. The current review summarizes the formation and growth (nucleation, growth and recrystallization) of ice crystals based on the dynamic transformation from water to ice to water, analyzes the morphological change in ice crystals induced by different temperatures and degrees of supersaturation and the dynamic transformation from water to ice to water during freezing-thawing. This review focuses on the mechanism by which the transformation from water to ice to water causes deterioration of the microstructure, water-holding capacity, oxidation stability (fat oxidation, protein oxidation and conformational change) and sensory quality (texture, color and flavor) of frozen meat. Finally, some emerging freezing technologies (ultrasound freezing, high-pressure freezing, electromagnetic freezing and adding cryoprotectant) used to improve the quality of frozen meat are briefly introduced. This review is expected to provide a scientific theoretical basis for improving the quality of frozen meat and its industrial production.