| Delicious and nutritious chicken soup has many physiological functions,which is a necessary supplementary food and base material in the catering industry,home cooking,medical care and other fields.As the pace of life is speeding up,while traditional cooking chicken soup is long,which limit the consumption of chicken soup.Therefore,the market prospect of delicious,nutritious and convenient instant frozen chicken soup is becoming more and more promising.At present,there are few studies on the effects of different thawing methods on chicken soup.Based on the above,this paper analyzed the effects of microwave thawing,high temperature water bath thawing(70 ?)and room temperature air thawing(25 ?)on the quality of chicken soup,and got the following results:(1)The-20 ?'s and-40 ?'s freezing rate curve of chicken soup accorded with the regular food freezing curve.The-20 ?'s freezing rate was 0.9375 cm/h,belonged to the slow freezing.The-40 ?'s freezing rate was 1.33 cm/h,belonged to the fast freezing.There was no significant difference in thawing time between the two frozen chicken soup in the same thawing mode,but there was significant difference in thawing time between different ways of thawing,which microwave thawing was the fastest,followed by high temperature water bath thawing,and room temperature air thawing was the longest.Mainly because thawing principle and thawing temperature was different.(2)The content of soluble protein,collagen and reducing sugar was the highest both in the two kinds of frozen chicken soup with the room temperature air thawing,but which was the lowest under the condition of thawing at high temperature water bath thawing.The high temperature water bath thawing group had the highest concentrations of oligopeptides and nucleotides,obviously differences with other thawing groups(P<0.05).The main reason was that the temperature of the thawing system at room temperature was slow,and the protein change in high temperature water bath was beneficial to the maillard reaction between the reducing sugars.The crude fat content of microwave thawing was higher than that of other two thawing processes,significant difference(P<0.05).The main reason was that the structure and force of the intermolecular structure were very huge,which led the material structure to become loose,and was beneficial to the melting of the fat.After thawing at room temperature,the content of soluble protein,collagen protein,reducing sugar and nucleotide group in the-40 ? freezing group were significantly greater than-20 ? freezing group.the faster freezing rate,the less chicken soup material lost.The faster the freezing rate,the less material lost.(3)After microwave and high temperature thawing,two kinds of frozen chicken soup both had a higher pH(P<0.05),but was the lowest after room temperature thawing.Due to the dissolution of free fat,frozen chicken soup had the largest b* value in the microwave thawing,and-20 ? slow freezing group was greater than the-40 ? frozen.After thawing of microwave and high temperature water bath,the content of electric conductivity and TBARS was highest,which was significantly greater than thawing at room temperature.After the high temperature and room temperature's thawing,the TBARS value in-20 ? freezing group was significantly greater than-40 ? freezing group(P<0.05),because rapid freezing can reduce the fat oxidation rate of chicken soup.Under the same shear rate,the chicken broth viscosity,shear stress of the-20 ? freezing group was greater than the-40 ? freezing group,and which was significantly higher than other thawing method.The viscosity trend line of two kinds of frozen chicken soup was almost completely overlaps in the microwave and high temperature water bath thawing.The shear stress of freezing chicken soup thawed both in the microwave and high temperature was no different within 300 r/s,while room temperature > high temperature water bath > microwave over 300 r/s.Chicken soup was a multivariate mixture,and rheological properties were affected by many factors.(4)The two kinds of frozen chicken soup had the highest levels of sulfhydryl group and the lowest carbonyl content at room temperature,which was significantly different from the other two thawing methods(P<0.05).It indicated that the low thawing temperature can reduce the degree of protein oxidation.The surface hydrophobicity and emulsification activity of the chicken soup were the lowest at the high temperature water bath thawing.The main reason was that the viscosity of the emulsion system decreased and the diffusion coefficient of the small droplets increased when the thawing temperature was high.The emulsification stability of room temperature thawing group was the highest.Under the same defrost mode,the carbonyl's content in the-20 ? freezing group was higher than-40 ? freezing group,and the surface hydrophobicity in the-20 ? freezing group was significantly lower than-40 ? freezing group(P<0.05).A total of 17 kind of amino acids were detected in frozen chicken broth,and the content of lysine,glutamate and serine were high.A heated thawing will help increase the essential amino acid content of chicken soup.The total free amino acids in all the experimental groups were over 50 %.Under high temperature water bath thawing,the content of sweet flavor amino acid content and bitter amino acid were both big,which indicated that the physical and chemical reactions of the high temperature thawing can promote the release of total free amino acids.The bitter taste of the proportion of amino acids thawed of-20 ? frozen chicken soup were greater than-40 ? frozen chicken soup(P<0.05).The percentage of hydrophobic amino acids in total free amino acids was about 9.05~9.94 %,and the percentage of hydrophilic amino acids was 63.98~70.37 %.The content of hydrophobic acid and hydrophilic amino acid of the frozen chicken soup were the highest with the high temperature water bath(P<0.05),and the least with the room temperature(P<0.05).(5)There were 12 main fatty acids in frozen chicken soup,and unsaturated fatty acids accounted for 50.97~62.12 % in them,especially the content of MUFA was the most.The content of MUFA and PUFA in the two groups of frozen chicken soup were the highest at room temperature(P(27)0.05),mainly because microwave and high temperature water bath thawing can cause unsaturated fat loss,while thawing at room temperature was beneficial to the maintenance of unsaturated fatty acid content.Besides three defrost mode: the content of PUFA of-20 ? freezing group were significantly lower than-40 ? freezing group(P<0.05),the main reason was that the content of linoleic acid of the-20 ? freezing group was significantly less than freezing group(P<0.05).The content of linoleic acid was the absolute advantage of polyunsaturated fatty acids in chicken soup,accounting for more than 94 %.Rapid freezing can significantly inhibit the oxidation of polyunsaturated fatty acids,especially linoleic acid.The thaw chicken soup were detected 94 kinds of volatile substances,and 47 kinds of them were found in all groups.The proportion of aldehydes was the highest,accounting for 60~82 %,followed by hydrocarbons.The total variation range of volatile compounds was 502.33 ~ 685.33 ug/100 mL.The content of aldehydes in the microwave thawing group was the highest,and the contents of hydrocarbons,acids,alcohols and esters were higher.Each group detected a significant contribution of 2-pentyl furan in the flavor of chicken broth,and the content was relatively high.The differences of flavor substances after thawing were mainly related to the freezing rate and thawing mechanism.Due to the difference of the thawing conditions,such as temperature and heat transfer,the damage degree of the flavor precursor was different,which resulted in the change of flavor composition.Under the condition of natural thawing at room temperature,the fast freezing method was more conducive to the maintenance of volatile flavor compounds.On the whole,the three kinds of thawing methods had different influence on each quality due to different conditions such as thawing principle and thawing temperature.Room temperature air thawing was more beneficial to reduce the loss of some nutrients and reduce the degree of protein oxidation.However,chicken soup was a multivariate mixture,so thawing mode had no significant effect on the physical and chemical effects of frozen chicken soup.High temperature water bath thawing group had the highest flavor amino acid content,sweet and delicious amino acid.The content of aldehydes in microwave thawing group was the highest,and its flavor was rich.Therefore,the future industrial production can can be personalized and targeted to choose thawing mode and thawing conditions to meet the market demand according to the different standards and requirements. |
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