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Huang Z.,Henan Agricultural University | Huang Z.,Henan Key Laboratory Cultivation Base of Quick Frozen Flour Rice Food and Prepared Food | Qi G.,Henan Agricultural University | Ai Z.,Henan Agricultural University | And 5 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2015

In order to improve the quality of dumplings and explore the role of liquid nitrogen on regulating food quality, an experiment was conducted with dumplings as the research object, which was made of dough, meat and stuffing water. However, there were some differences in the water content, enthalpy and freezing rate in each component, therefore, and the dumpling-cracking rate itself was a complex manifestation, which in the meantime could also be affected by the quality of flour, ratio of raw materials and specifications etc. This study was aimed at understanding how the amount of water when kneading dough, the incubation time of the finished dough, the dumpling wrapper and meat stuffing ratio and the immersion time of dumplings in liquid nitrogen pool affected the cracking rate of the dumplings, which took pork, mushrooms and soy protein as the main raw material of dumpling stuffing. The result showed that the water amount of the flour had great influence on the gluten network formation of dumpling wrapper and dough processing characteristics. The dumplings from the same batch in the process of quick freezing tunnel method had far lower cracking rate than the liquid nitrogen freezing technology. Compared with freeze tunnel, being frozen in liquid nitrogen would have shorter freezing time and faster shaping time. Regardless of the water amount in dough, according to the water distillation principle, outer layer of wrapper would appear to be white powder layer, and the dumpling wrapper whiteness improved significantly (P<0.05) when frozen in liquid nitrogen (fresh 83; frozen 85; liquid nitrogen 88). Liquid nitrogen freezing method for food preservation and quality improvement is better than quick freezing tunnel method. Through the construction of the relationship between dough sensory and texture characteristics, the dough elasticity in industrial production could be expressed by texture determination, rather than relying on the subjective factors from experienced workers. Also in order to reduce or eliminate the dumpling-cracking rate, it could not only control the selection of the flour, the water addition and the dumpling wrapper and meat-stuffing ratio etc., but also control the selection of additives (single and combined). Through market research, with the increase in air separation plants, liquid nitrogen production cost had been slashed, and the use of liquid nitrogen in the industrialized production of food would have good prospects. The result showed that there were some effects at different degree on dumpling cracking rate for the 4 factors above. The dumplings would have relatively low cracking rate (37%) and high quality (77.6) under mass ratio of water and flour was 56:100, less than 10 min incubation time of finished dough, 1:1.3 weight ratio of dumpling wrapper and meat stuffing and immersing in nitrogen pool for 40 s immediately after the dumplings were done. The study provides a theoretical reference for the application of liquid nitrogen on food process. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved. Source


Huang Z.,Henan Agricultural University | Huang Z.,Henan Engineering Laboratory of Quick Frozen Flour Rice Food and Prepared Food | Huang Z.,Henan Key Laboratory Cultivation Base of Quick Frozen Flour Rice Food and Prepared Food | Huang Z.,Quick frozen Food Research and Development Center | And 12 more authors.
Journal of Chinese Institute of Food Science and Technology | Year: 2014

In order to research the in vitro antibacterial activity of betaine on Staphylococcus aureus and its synergistic effect with storage temperature. The tube double dilution method was employed to determine the minimum bacteriostatic concentration (MIC) of betaine on S. aureus; and to compare the the growth curves at different concentrations of betaine. Finally, Gompertz model was used to calculate the growth characteristics of bacteria. Furthermore, the synergistic effects of variety of 37, 10, 42℃ and 45℃ along with betaine on the S. aureus growth curves were analysized in present study. The results indicated that the betaine had a significant inhibition towards S. aureus (P<0.05), and the MIC was 6.25 mg/mL. Higher concentration of betaine and lower treatment showed a better inhibition effect on growth of S. aureus. The growth dynamics models of S.aureus could be well described by a Gompertz type model, which showed an abvious influence of betaine concentration on μmax(maximum specific growth rate) and λ (lag phase). The fitted prediction models could provide a theoretical foundation for the development and utilization of betaine as a natural food preservative in future. ©, 2014, Chinese Institute of Food Science and Technology. All right reserved. Source


Suo B.,Henan Agricultural University | Suo B.,Henan Key Laboratory Cultivation Base of Quick Frozen Flour Rice Food and Prepared Food | Ju R.,Henan Agricultural University | Wang N.,Henan Agricultural University | And 4 more authors.
Journal of Chinese Institute of Food Science and Technology | Year: 2015

With the purpose of investigating the sublethal injury and stress resistance mechanisms of Stahpylococcus aureus during frozen storage, we determined the change rules in sublethal injury and physiological indicators were determined in present study, as well as the transcriptional expressions of clfA and msrR virulence genes by real-time PCR assay. As shown in the results, under the initial 0-90 d of -18℃ frozen storage, the total viable cell number of S. aureus gradually reduced along with an increase in sublethal rate. Meanwhile, the electric conductivity, leakage of protein, total sugar content and cell lysis rate all showed increasing trends. However, during the further 90-180 d of frozen storage, the total viable and non-injured viable cell counts of S. aureus were not decreased anymore. The electric conductivity, protein leakage and total sugar content kept constant level from 90-180 d of frozen storage. Real-time PCR results showed that, there were a significant increases in clfA and msrR gene transcription upon 90 d of frozen. During early cold stress, there happened a structural damage in membrane of S. aureus that lead to cell death. Where as cells under sustained low temperature stress can still maintain membrane integrity, a certain degree of biological activity and pathogenicity as well. © 2015, Chinese Institute of Food Science and Technology. All right reserved. Source

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