Influence of Frozen Storage Temperature on Quality and Microstructure of Frozen Pork Dumpling Filling
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Abstract:
The effect of different frozen storage temperatures on quality properties and microstructures of frozen pork dumpling fillings to reveal the mechanism underlying the changes in their quality was evaluated. Freshly prepared dumplings were frozen at -25 ℃ and then stored for 0 d, 30 d, 60 d, 90 d, or 180 d at -7 ℃, -18 ℃, and a temperature fluctuating between -7 ℃ and -18 ℃, respectively. The a*-value, b*-value, and the gel properties of myofibrillar protein were measured at an interval of 30 d, and the scanning electron microscopy (SEM) and paraffin sectioning of the dumpling filling were also performed. The results showed that with increasing frozen storage time, a*-value and b*-value of the dumpling filling was reduced significantly (p<0.05), the first peak storage modulus values (G′) of myofibrillar protein gel decreased, and Tanδ at the final heating stage increased. The SEM and paraffin section results indicated that the samples stored at -18 ℃ had a relatively fine and smooth texture, showing a lower degree of protein denaturation in the minced meat matrix. However, the texture of the samples stored at -7 ℃ and -7 ℃/-18 ℃ became coarse; the degree of protein denaturation and the emulsifying properties of the minced meat matrix increased and decreased, respectively; and there was a significant fat exudation. This finding indicated that a high (-7 ℃) storage temperature and a fluctuating storage temperature (-7 ℃/-18 ℃) caused deterioration of the dumpling quality. Therefore, a low-temperature and a short-term storage are necessary for the retail sales, transportation, and storage of frozen dumplings, in order to maintain a good quality.
