The Effect Of Freezing Storage Temperature And Freeze-thaw Cycles On The Storage Quality Of Pig Trotter

Pig trotter,which is nutritious and rich in collagen,has edible value and diet cure effect.It is popular food and freeze-preservation has been regarded as one of the best way to preserve pig trotter,so frozen pig trotter naturally has a broad market.In order to provide theoretical foundation for quality control of pig trotter during the freezing storage,the quality changes of pig trotter under different freezing temperature and the effect of freeze-thaw cycles(due to temperature fluctuations)on the quality were studied.The results are showed as follows:1.The effect of freezing temperature on the quality of pig trotter:TVB-N value,TBARS value,collagen content,pH value,moisture content,thawing loss rate,protein content,and sensory score of pig trotter stored at four different freezing temperature(-5?±1?,-10?±1?,-15?±1?,-20?±1?)were measured.The results showed that the quality of pig trotters at four temperature generally declined when the storage period exceeded 150d.There were significant differences(p<0.05)of various indicators of the pig trotters stored at different freezing temperature.The results showed a significant correlation between trotter quality changes and,time and temperature of freezing storage.The lower of the frozen storage temperature,and the shorter of the time,the smaller trotter quality changed.When the trotter was stored at-20?,the decline of sensory score,moisture content,protein content and collagen content were all small,pH value,TVB-N and TBARS value increased slightly,and thawing loss rate was low.In such case,the nutritious and edible value were well maintained.Thus,-20?±1? was considered to be the optimal freezing storage temperature for pig trotter.2.The effect of freeze-thaw cycles on the quality of pig trotter.TVB-N value,TBARS value,collagen content,protein content,pH value,moisture content,thawing loss rate,and sensory score were measured when pig trotter went through different freeze-thaw cycles(1 time to 6 times)during the storage at-20?±1?.The results showed that there were significant differences(p<0.05)of various indicators after the pig trotters being exposed to freeze-thaw cycle.As the number of freeze-thaw cycle increased,TVB-N value,TBARS value,thawing loss rate and pH value increased,protein content,collagen content and moisture content declined,and sensory score also went down.Therefore freezing and thawing cycle had large effects on the sensory score,edible value and nutritious value of pig trotters,resulting in the decline of the quality.The quality of pig trotters significantly declined after 3 times of freezing and thawing cycle.And the seriously deteriorated after six times freeze-thaw cycle,losing the value of goods.Thus,3 times of freeze-thaw cycle was quality turning point.During freezing storage,it is necessary to reduce the number of freezing and thawing cycle resulting from temperature fluctuations,and keeping the storage temperature stable could maintain the origin quality of pig trotters at maximum degree.Also,it is essential to decrease the number of freezing and thawing cycle caused by temperature fluctuations during the entire food cold chain including slaughtering,freezing storage,transportation and sales.Only keeping the circulation of the products under low temperature,the nutritious and edible value of pig trotters could be well maintained.Furthermore,the freeze-thaw cycles should be no more than 3 times,which can better keep the quality of pig trotters.