冻结方式对冷冻生坯包子品质的影响

    Effect of freezing methods on quality of frozen raw baozi

    • 摘要: 为探究生坯包子的最佳冻结方式,测定普通冰箱(RF-18 ℃)、传统速冻柜(TF-40 ℃)、液氮速冻柜(LNF-30~-90 ℃)、液氮浸渍冻结(IF-196 ℃)等方式的冻结速率及其对生坯面团流变学特性、游离巯基含量、可冻结水含量及微观结构的影响,测定生坯包子比容、质构特性并进行感官评价,分析冻结方式对生坯包子皮品质的影响。结果表明:冻结速率依次为IF-196 ℃(50.38 ℃/min)>LNF-90 ℃(7.01 ℃/min)>LNF-60 ℃(4.48 ℃/min)>LNF-50 ℃(3.66 ℃/min)>LNF-40 ℃(2.69 ℃/min)>LNF-30 ℃(1.49 ℃/min)>TF-40 ℃(1.30 ℃/min)>RF-18 ℃(0.38 ℃/min),冻结速率越快,生坯面团的可冻结水含量、水分分布状态及动态流变学特性越接近新鲜生坯面团;在IF-196 ℃、LNF-90 ℃、LNF-60 ℃、LNF-50 ℃条件下冻结的生坯面团发酵流变学特性、微生物活菌数以及蒸制后包子的比容、质构特性和感官品质发生劣变,而在LNF-40 ℃条件下冻结的生坯包子品质更接近新鲜包子。LNF-40 ℃冻结条件适合冷冻生坯包子的加工。

       

      Abstract: The freezing treatments had adversely affected the viable cell counts and the structure of the gluten network in the baozi dough, thereby deteriorating the baozi quality. To investigate the optimal freezing method for raw dough baozi, the freezing rates of various methods including conventional refrigerator freezing (RF-18 ℃), traditional quick-freezing cabinet (TF-40 ℃), liquid nitrogen quick-freezing (LNF-30 ℃, LNF-40 ℃, LNF-50 ℃, LNF-60 ℃, LNF-90 ℃), and liquid nitrogen immersion freezing (IF-196 ℃) were determined. The effects of these freezing methods on the rheological properties, moisture distribution, the content of free sulfhydryl groups and freezable water, and microstructure of the frozen dough were also assessed. Additionally, the freezing rates, specific volume, texture properties, and sensory evaluation of the frozen raw baozi were determined to analyze the impact of freezing methods on the quality of the bao wrapper. The results showed that the freezing rates were in the order of IF-196 ℃ (50.38 ℃/min)>LNF-90 ℃ (7.01 ℃/min)>LNF-60 ℃ (4.48 ℃/min)>LNF-50 ℃ (3.66 ℃/min)>LNF-40 ℃ (2.69 ℃/min)>LNF-30 ℃ (1.49 ℃/min)>TF-40 ℃ (1.30 ℃/min)>RF-18 ℃ (0.38 ℃/min). Faster freezing rates resulted in the freezable water content, water distribution, and dynamic rheological properties of the raw dough more closely resembling those of fresh raw dough. However, the fermentation rheological properties, viable count of yeast, the maximum dough fermentation height, the maximum height of the gas emission curve, and the total gas volume were quite different from fresh dough. Raw baozi when frozen under IF-196 ℃、LNF-90 ℃、LNF-60 ℃, and LNF-50 ℃ were significantly higher, the elasticity was significantly lower than other freezing methods, and the quality deteriorated in terms of flavor and color. The viable count of yeast, the maximum dough fermentation height, the maximum height of the gas emission curve and the total gas volume of dough, the specific volume, the texture and the sensory scores of baozi through LNF-40 ℃ were significantly higher than other freezing methods. The quality of raw baozi through LNF-40 ℃ was closer to fresh baozi. Therefore, LNF-40 ℃ is a suitable freezing method for the processing of frozen raw baozi.

       

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