Quality changes and mechanism of frozen non-fermented dough upon consecutive freeze-thaw cycles

Abstract: In order to investigate the effect of consecutive freeze-thaw (FT) cycles on the qualities of frozen non-fermented dough during the process of the storage, transportation and sale, the low-field nuclear magnetic resonance (LF-NMR), a texture analyzer and a rheometer were used to observe changes of frozen non-fermented dough in quality during five consecutive freeze-thaw cycles. The water loss rate, water distribution and mobility, protein fraction content, textural and rheological properties of the dough samples were evaluated in our experiment. The results showed that: upon five consecutive FT cycles, the water loss rate significantly increased to 3.14% (P＜0.05), while the ratio of semi-bound water to the total water declined in general, indicating that the water losing was mainly resulted by the semi-bound water release. The gliadin content significantly decreased (P＜0.05) at the fifth FT cycles; the glutenin and glutenin macropolymer (GMP) content experienced an obvious drop after the forth FT cycles and down to 2.26% and 0.70%, respectively. For uncooked samples, firmness obviously increased and toughness was on the contrary; for cooked samples, hardness increased at first and then decreased, adhesiveness presented ascendant trend basically and springiness declined. The storage moduli and loss moduli (G' and G'') both showed a downward trend, and at the forth FT cycles, tan δ (tan δ = G' / G'') was up to the maximum, which indicated that G' showed a more dramatic drop than G''. From these results, it was thus clear that the consecutive FT cycles led to the decrease in the quality of frozen non-fermented dough. Overall, the consecutive freeze-thaw cycles had certain negative effect on the qualities of frozen non-fermented dough.