Dry-cured meat products are considerably popular around the world due to unique flavor. Proteolysis is one of the enzymatic reactions from which flavor substances are derived, which is affected by endogenous proteases. The purpose aimed to reveal the potential relationship between endogenous proteases and key flavor substances in dry-cured pork coppa in this paper. The dynamic changes of endogenous proteases activity, free amino acids, and volatiles during dry-cured pork coppa processing were characterized. The results showed that 5 kinds of free amino acids, Glu, Lys, Val, Ala, and Leu, were identified as significant contributors to taste. Meanwhile, key volatiles, such as hexanal, nonanal, octanal, benzaldehyde, 3-methyl butanoic acid, 2-methyl propanoic acid, and ethyl octanoate, greatly contributed to the flavor characteristics of dry-cured pork coppa. Further partial correlation analysis was performed to better elucidate the relationship among parameters. The results revealed that close relationship between endogenous proteases and key substances. RAP not only significantly affected the accumulation of key active-amino acids, but also affected the accumulation of ethyl octanoate, 2,3-pentanedione, and 2,3-octanedione by regulating the accumulation of octanoic acid and Leu. In addition, cathepsin B and D, DPP Ⅱ, DPP Ⅳ and RAP notably affected accumulation of hexanal.

Dry-fermented sausages are a good source of bioactive peptides, whose stability against gastrointestinal (GI) digestion determines their bioaccessibility. This study focused on evaluating the effect of peptide extracts from sausages fermented with Staphylococcus simulans QB7 during in vitro simulated GI digestion, including peptide profiles and antioxidant and anti-inflammatory activities. Peptides present in sausages were degraded during digestion, with molecular weight reduced from > 12 kDa to < 1.5 kDa. Besides, the content of amino acids increased from 381.15 to 527.07 mg/g, especially tyrosine being found only after GI digestion. The anti-inflammatory activities were increased after GI digestion, however, the changes in antioxidant activities were the opposite. A total number of 255, 252 and 386 peptide sequences were identified in undigested, peptic-digested and GI-digested samples, respectively. PeptideRanker, BIOPEP-UWM and admetSAR were used to further predict the functional properties and intestinal absorption of the identified peptide sequences from GI digestion. Finally, 18 peptides were discovered to possess either antioxidant or anti-inflammatory capacities.

Staphylococcus simulans ZF4 and Lactobacillus plantarum SJ4 were screened from locally obtained food in Guizhou and then used to fermented pork loins. The effects of the starters on the quality of the fermented pork loins were explored through physicochemical analysis as well as E-nose and E-tongue assessments. High-throughput sequencing technology was used to reflect the distribution and function of the starters culture flora during the fermentation processes. The results showed that the starters conferred more well-rounded sensory qualities to the fermented pork loins, including improvements in their color, aroma, and other qualities. In addition, Corynebacterium variabile, Pediococcus pentosaceus, Lactococcus garvieae, Staphylococcus vitulinus, Bacillus velezensis, and Leuconostoc mesenteroides can be found to be inhibited by the starters (Staphylococcus simulans ZF4 and Lactobacillus plantarum SJ4), thereby improving safety of fermented pork loins. Moreover, throughout the fermentation process, Staphylococcus simulans ZF4 appeared to provide a stronger umami taste to the fermented pork loin, and the Lactobacillus plantarum SJ4 was better at producing flavor substances.

Freeze-drying technology is widely used in strain preservation. To further improve the survival rate of Lactobacillus plantarum SJ-4 after freeze-drying, an experimental design based on the Plackett-Burman method, steepest ascent hill climbing, and the Box-Behnken response surface methodology (RSM) was used to obtain the freeze-dried powder with a viable bacteria count of 10¹⁰ CFU/g. The lyophilized powder of L. plantarum SJ-4 prepared was applied to fermented tenderloin ham. High-throughput sequencing was used to analyze the structural changes and succession patterns of bacterial communities and discuss the effects of inoculation on the bacterial phase in tenderloin ham. The results showed that this direct-vat-set starter can improve the fermented meat flora and promote the production of beneficial bacteria, providing a theoretical basis for the in-depth development of the functional properties of the strains and the deep processing of meat products in the future.

Yeasts play a critical role in the flavor formation of dry-cured ham. In this study, 41 yeast isolates from the dry-cured ham at different processing stages were evaluated for their technological properties. Debaryomyces hansenii was the most dominant yeast and has been detected at each phase of dry-cured ham, followed by Candida zeylanoides which was mainly detected in salting phase. Yarrowia bubula and Yarrowia alimentaria were found at the first two-phase of dry-cured ham. All isolates of yeast showed enzymatic activities against milk protein and tributyrin, while only 4 strains displayed proteolytic activity on meat protein. Yeast strains were grown in a meat model medium and volatile compounds were identified. The result showed that inoculated yeast strains could promote the production of volatiles and there were significant differences among strains. D. hansenii S25 showed the highest production of volatile compounds, followed by the strain C. zeylanoides C4. D. hansenii S25 was the highest producer of alcohols showing the highest production of benzeneethanol and 3-(methylthio)-1-propanol. Based on OAV and PLS analysis, D. hansenii S25 was strongly correlated with overall flavor and key volatile compounds of dry-cured ham, which could be selected as potential starter cultures.

The hazardous substance Neu5Gc (N-glycolylneuraminic acid), which is rich in red meat, is related to chronic inflammation but is hard to eliminate. Here, electrical stimulation, as a food-friendly nonthermal processing technology, was applied to red meat samples to reduce the Neu5Gc content. To explore the Neu5Gc structure changes during this process, electronic structure parameters were evaluated, and AIM (atom in molecules) theory and DFT (density function theory) calculations were further used. The results showed that the content of Nue5Gc in red meat can be reduced by (74.24 ± 0.69)% at 120 V for 50 s, with little impact on the meat texture and color. Theoretical calculations indicated that the Neu5Gc molecule becomes very unstable under electrical stimulation by increasing the OH bond length, reactive activity, strength of intermolecular dipole forces and total energy through reducing the values of bond dissociation energy and strength of intramolecular hydrogen bonds. Overall, this research provides an economical method to effectively control red meat safety.