Effect of inoculating mixed starter cultures of Lactobacillus and Staphylococcus on bacterial communities and volatile flavor in fermented sausages

The objective of this study was to explore the effects of the inoculation of mixed starter cultures of Lactobacillus and Staphylococcus(labeled L-S)on microbial community and flavor in fermented sausages during the ripening process.Culture-dependent(colony count)and culture-independent(high-throughput sequencing)methods were employed to evaluate bacterial communities.Volatile compounds were identified by gas chromatography-mass spectrometry,and the results were analyzed by principal component analysis(PCA).The identified bacteria with high relative abundance included Lactobacillus and Pediococcus,and the relative abundances of Leuconostoc and Weissella in fermented sausages were remarkably decreased at the end of the ripening process.At the end of ripening,2-nonenal,tetradecanal,ethylstearate and terpinyl acetate played substantial roles in the flavor development of the L-S fermented sausages.Sensory evaluation showed a high score in the L-S fermented sausages.Sausages can be inoculated with L-S starter culture to improve the safety and flavor of meat products.

Performance of novel overhead crane fume-collecting hood for pollutant removal

In industrial buildings,the presence of overhead cranes severely affects roof exhaust ventilation systems when capturing and discharging fumes,resulting in severe deterioration of the indoor plant environment.In this study,an overhead crane-based ventilation auxiliary device,called overhead crane fume-collecting hood(CFCH),is proposed to guide pollutants blocked by the overhead crane back to the roof exhaust hood.The airflow characteristics and pollutant distribution under the three modes of no overhead crane,overhead crane,and overhead crane+CFCH were compared using numerical simulations.Subsequently,the effects of the CFCH length(a),width(b),and height(h)on the pollutant capture performance were determined through orthogonal experiments and computational fluid dynamics.Finally,the pollutant capture efficiency(PCE)of the optimal CFCH was investigated considering different exhaust airflow rates.The results showed that the pollutants captured by the CFCH can be classified into directly and secondary captured pollutants,with the directly captured pollutants dominating.In addition,with the introduction of different sizes of CFCH around the overhead crane girders,the PCE significantly improved by 49.9%–74.6%.The length,width,and height of the CFCH on the PCE were statistically significant,and the priority of the three factors was as follows:h>b>a.The PCE decreased with increasing a,initially increased and then decreased with increasing b,and increased with h.Subsequently,when the optimal CFCH was used,the excessive exhaust air rate had no evident PCE improvement.This provides a new concept for the control of pollutants in industrial buildings and provides a theoretical basis for the design of CFCHs.

Selection of nitrite-degrading and biogenic amine-degrading strains and its involved genes

Objectives:Accumulation of nitrite and biogenic amines(BAs)in fermented meat products is a matter of public health concern.The study aimed to screen nitrite-degrading and BA-degrading strains from sour porridges and sausages and bacon products in China.Materials and Methods:After screening out 12 strains,the degradation of nitrite,the degradation of BAs,the activities of nitrite-reducing enzymes,and the detection of genes involved in the BAs were assessed by spectrophotometry method with hydrochloric acid naphthalene ethylenediamine,high-performance liquid chromatography,GENMED kit,and polymerase chain reaction,respectively.Results:Pediococcus pentosaceus labelled M SZ12 and M GC 2,Lactobacillus plantarum labelled M SZ22,and Staphylococcus xylosus labelled Y CC 3 were selected.The activity of nitrite-reducing enzyme in M SZ22 was 2.663 units/mg.The degradation rate of total BAs of M SZ22 was 93.24%.The degradation rates of nitrite and BAs of M SZ12 were 86.49%and 37.87%,respectively.The activity of nitrite-reducing enzyme in M SZ12 was up to 1.962 units/mg.M GC 2 showed higher degradation rates of nitrite(89.19%)and Y CC 3 showed higher degradation rates of BAs(36.16%).The genes encoding the multicopper oxidases(suf I/D2EK17)were detected in the four strains,which also did not contain BAs(histidine decarboxylase(hdc),tyrosine decarboxylase(tdc),ornithine decarboxylase(odc),lysine decarboxylase(ldc))formation encoding genes.Conclusion:These four strains(M SZ12,M GC 2,M SZ22,and Y CC 3)are promising candidates to use as starter cultures for nitrite and BAs in fermented sausages.