Study On Glass Transition Temperature And Quality Of Beef Frozen Storage

The vitrification of food has become a hot spot in the field of food processing,but most of the current limited to a single component and theoretical research.The study of the Tg of complex food systems and their impact on food quality and shelf life is not sufficient.The glass transition research at home and abroad rarely reported beacause of its complex ingredients and high levels of moisture.In order to improve the glass transition temperature and further verify the effect of vitrified state storage on the quality of complex food,we selected beef as the experimental object and analyzed the physical and chemical indexes and sensory quality change above and below the Tg in this paper.LF-NMR was used to analyze the change of water content and its migration in different states during the process of beef storage and the influence of different macromolecules(sucrose,inulin,D-sorbitol,D-trehalose)on Tg were studied in detail,At the same time,using the Arrhenius equation to predict the shelf life.The results are as follows:(1)Beef g was measured at-14 ? by DSC and stored at-10 ?(>Tg),-14 ?(=Tg),-18 ? and-22 ?(<Tg)for 7 Month,the effects of vitreous storage on the quality of beef were studied by measuring the color parameters,tenderness,total number of colonies and TVB-N in the process of beef storage.The results showed that:the L*value(-14 ?,-18 ?,-22 ?)was stable over the time,and the a*value decreased at the early stage of storage(the first month)and b*gradually increased.L*value(-10 ?)decreased significantly,a*value gradually decreased and was higher than that of the other three kinds temperature(P<0.01).The overall shear force increases first and then decreases,But at the later stage of storage,the shear force of beef at-10 ? and-14 ? decreased sharply,close to the initial value;The overall number of colonies is on the rise,and the number of colony at-10 ? in the first 5 months was significantly different from that of the other three kinds of temperature(P<0.05).TVB-N value gradually increased witin the storage time,Beef stored at-10 ? for 4 months from fresh meat to secondary freshness while stored at-14 ?,-18 ?,-22 ? for 6 months into secondary freshness.(2)Determination of transverse relaxation time T2 and peak area of beef based on LF-NMR technique.The results showed that:there were four different water groups in meat samples and the T2 content of beef was decreased obviously at-10 ?,explained that the free water content was significantly decreased while the relaxation time of beef was not changed obviously under Tg.At first,pT22 at a decline trend and latter become more stable,indicating that with the extension of storage time,not easy to flow water gradually transferred to free water.pT23 decreased first and then increased,finally decreased significantly(p<0.01).Through the analysis of the correlation between beef quality index and nuclear magnetic resonance parameter T2,It was found that the cooking loss was significantly correlated with T20,T22 and pT23(p<0.05),and the correlation coefficients were 0.777,0.745 and 0.783 respectively.Therefore,according to T22 and pT23 to represent water retention changes of beef in the process of storage.Through the nuclear magnetic imaging experiments found that beef storaged at-10 ? had a serious dry consumption and poor meat retention,This explained that-10 ? is not a good condition for long-term storage to beef.(3)The Tg value of beef was measured which were added different macromolecules by DSC,we also established dynamic model of beef quality(TVB-N)to predict the shelf life.The results showed that:Tg decreases first and then increases,finally become stable with the increase of water activity and moisture content;Inulin can effectively improve beef Tg value;the stability of beef stored at Tg or below Tg was better in the first 5 months.The proposed storage temperature is-14 ? hile beef storage period within 5 months,Storage temperature of-18 ? is ideal if the storage time more than 5 months while considering the beef quality and production cost.The food storage temperature T?Tg which will lead to the system in a glassy state and the strongest stability at this time was verified.Beef storaged at-18 ? and-22 ? was confirmed that there is no certain quality difference.