冰结构蛋白对长期冻藏冷冻面团抗冻发酵特性与超微结构的影响

本实验采用质构分析仪、扫描电镜以及冷冻面团烘焙发酵试验法研究了冰结构蛋白（ISP）对长期冻藏冷冻面团抗冻发酵特性与超微结构的影响。结果发现：将面团在-18℃冻藏0、35、70、105d后,随冻藏时间延长,面团醒发时间延长,面包比容减小。添加0．5％ISP的面凼,经105d冻藏后,醒发时间由153min缩短到130min,缩短了15．0％;面包比容由4．05ml／g上升到4．71ml／g,上升了16.3％,并且ISP使面包硬度有所减小。扫描电镜实验表明：强化0．5％ISP的冷冻面团,经过105d的冻藏后,仍然可以观察到明显的面筋网络结构,这说明ISP可以显著保护冷冻面凼超微结构。     

海藻酸钠对冷冻面团面包烘焙特性的影响

研究添加不同比例(0.1%、0.3%、0.5%和0.7%)海藻酸钠对冷冻面团面包烘焙特性的影响。结果表明,添加海藻酸钠能提高冷冻面团的持水率,减少冷冻面团醒发时间;增大面包的比容,降低面包的硬度和咀嚼性,提高弹性,改善冷冻面团面包的品质。感官评定显示,冻藏不同天数后,添加0.3%的海藻酸钠面包感官评分值最高。     

海藻酸丙二醇酯对全麦冷冻面团冻藏稳定性和烘焙特性的影响

本文研究了海藻酸丙二醇酯（Propylene glycol alginate,PGA）对全麦冷冻面团冻藏期间稳定性的影响,并探究了冷冻面团烘焙面包品质的变化。将0.3%的PGA加入全麦面团,通过测定冷冻面团冻藏1、2、3、4和5周后发酵特性、流变特性、蛋白质二级结构、微观结构以及面包的比容、质构特性、内部纹理结构和老化程度等,研究冷冻面团冻藏期间的稳定性。结果表明,随着冻藏时间的延长,添加PGA的冷冻面团在冻藏5周后具有较好的保水性,其发酵特性及流变特性相对于对照组均有所改善。冻藏5周后,对照组与PGA组其面包比容分别下降了19.872%和14.153%;面包硬度分别升高了64.186%和36.386%;气孔表面积分率分别下降了3.497%和2.300%;老化焓值分别上升了65.142%和42.416%。添加PGA能延缓冷冻面团冻藏期间β-折叠含量的上升和β-转角相对含量的下降。电镜扫描图（SEM）显示,随着冻藏时间的延长,PGA组的冷冻面团孔洞数目相比对照组明显减少且大小均匀,面筋网络结构完整性和连续性提高。研究结果表明PGA可以有效地延缓冷冻面团在冻藏期间的品质劣变,维持冷冻面团的稳定性并提高面包的烘焙特性。     

不同分子结构的黄原胶对冷冻面团及面包特性的影响

为研究不同分子结构的黄原胶对冷冻面团品质和面包烘焙特性的影响,该研究将3种不同分子结构的黄原胶分别添加至面粉中制作面团,经冷冻贮藏后进行面包焙烤,测定面团发酵速率、流变学特性、热稳定性及面包比容、硬度、弹性等。结果显示：随着冻藏时间的延长,面团品质及面包烘焙特性均受到影响,添加黄原胶显著降低面团劣变程度、改善面包品质。流变学结果表明,添加黄原胶增加面团黏弹性,抑制淀粉糊化;质构结果表明,黄原胶的添加显著增加面包的弹性,降低面包硬度（P<0.05）;比容结果显示,黄原胶的添加可以显著增加冷冻面团面包的比容（P<0.05）;低分子量黄原胶对面包品质改善效果较好。综上,在冷冻面团中添加黄原胶,可以得到品质较好的冷冻面团面包,且较低分子量黄原胶（1 400 kDa）不仅能改善面包焙烤特性,还可以降低实际生产应用过程中的时间成本。     

冷冻速率对面团发酵和烘焙性质的影响

研究了冷冻速率对冷冻面团体系中酵母发酵(包括酵母产气力、酵母存活率)和面团微结构的影响;以及对冷冻面团烘焙性质的影响(包括面包比容,面包评分和面包保质期).结果显示冷冻速率同时影响酵母活力和面团的超微结构,进而影响面包的品质和体积,综合考虑,确定面团在-32℃下快速冷冻至-18℃(冷冻速率约-5℃/min),并在-18℃下冻藏,较适合冷冻面团的生产.     

海藻糖和卡拉胶寡糖对冷冻面团冻藏稳定性和烘焙特性的影响

为了提高冷冻面团和面包的产品品质，将不同比例的海藻糖(1%、1.5%、2%,质量分数)和卡拉胶寡糖(0.3%、0.5%、0.8%,质量分数)加入面团，通过测定冻藏0、2、4周后冷冻面团的发酵特性、流变特性、水分分布、蛋白质二级结构、微观结构以及面包的比容、质构和内部纹理结构特性，研究冷冻面团冻藏期间的稳定性及面包烘焙特性。结果表明，随着冻藏时间的延长，添加海藻糖和卡拉胶寡糖的冷冻面团在冻藏4周后，其发酵特性及流变特性相对于对照组均有所改善。冻藏4周后，对照组、海藻糖-1.5%组、卡拉胶寡糖-0.5%组α-螺旋相对含量分别下降了45.73%、27.13%、15.71%;β-折叠相对含量升高了31.32%、15.51%、13.79%。电镜扫描图显示，随着冻藏时间的延长，海藻糖和卡拉胶寡糖组的冷冻面团相比对照组具有更致密的网络结构。对照组、海藻糖-1.5%组、卡拉胶寡糖-0.5%组在冻藏1个月后其面包比容分别下降了30.86%、21.48%、15.80%。综上，卡拉胶寡糖相对于海藻糖对冷冻面团冻藏稳定性及烘焙特性具有更好的保护效果，可作为一种新型抗冻剂用于冷冻面团生产中。     

解决冷冻面团技术难题的新原料——海藻酸钠

随着连锁经营概念普及,冷冻面团技术在全世界得到迅速的发展。冷冻面团的出现不仅可以降低生产成本、使产品质量更易标准化,工业产权更易受保护,而且可使产品更新鲜、稳定、安全性更高,同时还能有效解决面包老化等问题,这给面包乃至整个烘焙食品行业的发展注入了新希望、新生机。冷冻面团技术在带来诸多优点的同时,也带来了新的技术难题。在长期冻藏过程中,冰晶破坏面筋网络结构,面团持气能力下降,酵母活力下降,产气能力降低,导致冻藏后面包的比容减小、面包质地变差等,使冷冻烘焙产品品质降低。海藻酸钠的加入可以很好的解决这一技术问题。     

γ-聚谷氨酸提高冷冻甜面团面包质构和感官特性研究

研究了一种通过生物发酵制得的多聚氨基酸——γ-聚谷氨酸(γ-PGA)对冷冻甜面团抗冻活性和冷冻甜面团面包质量的影响。主要采用差示扫描量热仪(DSC)、质构仪和感官评定等方法研究了γ-PGA的抗冻活性、γ-PGA添加量和冻藏条件(恒温冻藏和冻融循环)对冷冻甜面团中可冻结水含量、面包比容、质构和感官品质的影响。结果表明,γ-PGA的抗冻活性值为8.027g不可冻结水/g,说明其具有非常好的抗冻活性;恒温冻藏和冻融循环后,冷冻甜面团中可冻结水含量明显增多,面包比容显著减小,质构变差,感官品质下降,尤其是冻融循环后,这种变化趋势更为明显;在相同冻藏条件下,添加0.5%和1%γ-PGA后,冷冻甜面团中可冻结水含量显著减少、冷冻甜面团面包比容显著增大、面包质构明显改善、面包感官评分明显提高,其中以1%γ-PGA的作用效果最好。     

冷冻面团发酵技术在中式食品中的应用II．冰结构蛋白对鲜酵母及包子类冷冻面团流变发酵特性的影响

应用F3 流变发酵仪和动态流变仪研究冰结构蛋白(ISP)对冻藏0、1、2、3、4 周鲜酵母发酵特性和冷冻面团动态流变学特性的影响。结果表明：随着冻藏时间延长,所有酵母样品发酵过程中气体释放曲线最大高度H′m、产生CO2 气体总体积V总及面团最大膨胀高度Hm 均逐渐降低,冷冻面团的弹性模量(G′)和黏性模量(G 〞)逐渐下降,冷冻面团包子比容显著减小。引入冰结构蛋白(ISP)后,冻藏时间相同时,酵母发酵过程中的H′m、V 总及Hm 均有所增大,G′和G 〞下降趋势减缓,冷冻面团包子比容明显大于空白组,说明ISP 能够抑制冻藏过程中冰晶的形成和重结晶,减弱冰晶对酵母及面筋蛋白质网络结构的破坏,同时也说明ISP 能够增强面筋蛋白质网络结构的强度,提高面筋蛋白质对冰晶破坏的抵抗力。     

三种甘油酯对冷冻面团及其面包品质的对比分析

本文通过核磁共振测定冷冻面团及其面包的水分迁移情况,流变仪测定冻藏过程中冷冻面团的流变学特性,质构仪和扫描仪分析面包的品质,研究三种甘油酯:乙酰化单、双甘油脂肪酸酯(ACETEM),双乙酰酒石酸单双甘油酯(DATEM)和六聚甘油单油酸酯,对冷冻面团及其面包品质的影响。结果表明:在冻藏过程中,三种甘油酯对冷冻面团及其面包的品质均有改善。与对照组相比,冻藏前三种甘油酯增加了面团及其面包的结合水比例,分别是面团增加了4.21%、7.02%、11.23%和面包增加了0.27%、4.67%、16.00%。而冻藏后,三种甘油酯降低了冷冻面团及其面包的水分迁移。在冻藏期间,冷冻面团的粘弹性降低,它们的损耗角正切值(tanδ)增加,发酵后对照组面团的tanδ增加了11.90%,添加了0.5%ACETEM面团的tanδ仅增加了4.76%。冻藏60d后,含0.5%ACETEM的面包比容为3.29m L/g,比对照组增大了23.50%;面包硬度为2298.92g,比对照组柔软19.18%。因此,添加了0.5%ACETEM的改善效果最好。     

寒地冬小麦冰结构蛋白的提取及抗冻活性的检测

以东农冬麦1号寒地冬小麦面粉为原料,利用磷酸盐缓冲溶液结合冰提法提取寒地冬小麦冰结构蛋白,通过单因素和响应曲面实验,得到提取寒地冬小麦冰结构蛋白的最佳工艺为:料液比1∶15,磷酸盐缓冲溶液浓度为10 mol/m L,p H7.8,搅拌时间2 h,冰球用量10个,冰提时间2 min,冰提温度-10℃,在此条件下对寒地冬小麦冰结构蛋白溶液进行复提,复提三次得到寒地冬小麦冰结构蛋白,提取率为18.2%。将寒地冬小麦冰结构蛋白进行浓缩,制成冻干粉,复溶至5%,对其进行冰晶观察,检测寒地冬小麦冰结构蛋白的抗冻活性,结果显示,寒地冬小麦冰结构蛋白复溶液冰晶排列整齐,形态各异,具有很好的抗冻活性。将其应用到冷冻面团中,面团品质得到了较好的改善。      

Freezing and Ice Recrystallization Properties of Sucrose Solutions Containing Ice Structuring Proteins from Cold-Acclimated Winter Wheat Grass Extract

ABSTRACT: The freezing properties of sucrose solutions containing ice structuring proteins (ISPs) from cold-acclimated winter wheat grass extract (AWWE) were evaluated. Neither significant ice nucleation nor thermal hysteresis activity in unpurified AWWE were detected ( P > 0.05). Ice recrystallization in sucrose solutions was assessed by bright field microscopy. Ice crystal growth was significantly reduced with the addition of more than 0.05% total protein from AWWE in 23% sucrose solutions frozen under static conditions and temperature cycled under long periods of time (60 min). Ice recrystallization inhibition was not evident when the samples were temperature cycled for shorter periods of time (10 min), indicating that an adsorption time may be required for the ISPs to be significantly active. The ice recrystallization was reduced with the increased on ISP concentration until reaching a plateau after adding 0.13% total protein from AWWE, representing a surface coverage of 9 mg protein/m² ice (assuming 100% adsorption). The reduction of ice crystal growth was as high as 74% compared with the control. This ice recrystallization inhibition offers significant opportunity for the use of ISPs from AWWE in frozen foods.     

结晶原理和冰淇淋中的结晶现象

阐述了结晶原理在冰淇淋凝冻中的应用,详细叙述了结晶的目的和方法,晶核的形成原理,结晶体的成长,多晶现象,以及冰淇淋中的结晶现象.     

Effect of storage temperature on quality of light and full-fat ice cream

Ice cream quality is dependent on many factors including storage temperature. Currently, the industry standard for ice cream storage is −28.9°C. Ice cream production costs may be decreased by increasing the temperature of the storage freezer, thus lowering energy costs. The first objective of this research was to evaluate the effect of 4 storage temperatures on the quality of commercial vanilla-flavored light and full-fat ice cream. Storage temperatures used were −45.6, −26.1, and −23.3°C for the 3 treatments and −28.9°C as the control or industry standard. Ice crystal sizes were analyzed by a cold-stage microscope and image analysis at 1, 19.5, and 39 wk of storage. Ice crystal size did not differ among the storage temperatures of light and full-fat ice creams at 19.5 or 39 wk. An increase in ice crystal size was observed between 19.5 and 39 wk for all storage temperatures except −45.6°C. Coldness intensity, iciness, creaminess, and storage/stale off-flavor of the light and full-fat ice creams were evaluated at 39 wk of storage. Sensory evaluation indicated no difference among the different storage temperatures for light and full-fat ice creams. In a second study, light and full-fat ice creams were heat shocked by storing at −28.9°C for 35 wk and then alternating between −23.3 and −12.2°C every 24 h for 4 wk. Heat-shocked ice creams were analyzed at 2 and 4 wk of storage for ice crystal size and were evaluated by the sensory panel. A difference in ice crystal size was observed for light and full-fat ice creams during heat-shock storage; however, sensory results indicated no differences. In summary, storage of light or full-fat vanilla-flavored ice creams at the temperatures used within this research did not affect quality of the ice creams. Therefore, ice cream manufacturers could conserve energy by increasing the temperature of freezers from −28.9 to −26.1°C. Because freezers will typically fluctuate from the set temperature, usage of −26.1°C allows for a safety factor, even though storage at −23.3°C did not affect ice cream quality.     

Effect of biopolymers on structure and ice recrystallization in dynamically frozen ice cream model systems

Ice crystal growth and microstructure of sugarsolutions prepared with stabilizers (carboxymethyl cellulose [CMC], xanthan gum, locust bean gum [LBG], and gelatin) with or without milk solids-nonfat (MSNF) after freezing in a scraped surface heat exchanger and temperature cycling (5 cycles from -6 degrees C to -20 degrees C) were studied. Ice crystal growth was calculated from brightfield microscopic images acquired from samples before and after cycling. Freeze-substitution and low-temperature embedding (LR-Gold resin) were sample preparation techniques utilized for structure analyses by light microscopy and transmission electron microscopy. Differential staining for carbohydrates and proteins allowed the identification of stabilizer gel-like structures in LBG, gelatin, and gelatin/MSNF solutions. In the absence of milk proteins, xanthan and LBG were the most effective at retarding recrystallization, while in their presence, only xanthan had an effect. Cryo-gelation of the LBG was observed but is not the only mechanism of stabilizer action. Thermodynamic incompatibility between biopolymers was observed to promote localized high concentrations of milk proteins located at the ice crystal interface, probably exerting a water-holding action that significantly enhanced the stabilizer effect. Qualitatively, solution heterogeneity (phase separation) was directly proportional to ice crystal growth inhibition. It is suggested that water-holding by stabilizer and proteins, and in some cases steric hindrance induced by a stabilizer gel-like network, caused a reduction in the kinetics of the ice recrystallization phenomena and promoted mechanisms of melt-regrow instead of melt-diffuse-grow recrystallization, thus resulting in the preservation of the ice crystal size and in a small span of the ice crystal size distribution.     

臭氧冰与电解水冰处理延长鲳鱼的冷藏货架期

为了研究臭氧冰与电解水冰对东海白鲳的保鲜效果,本文采用浓度为0.89mg/kg的臭氧冰与电解水冰（p H:2.49±0.01、ORP=（1115.0±0.5）mv、ACC=（28±1）mg/kg）处理鲳鱼后贮藏于1℃环境中,以普通冰处理作为对照。通过感官评定、菌落总数（APC）、挥发性盐基氮（TVB-N）值、p H、三甲胺氮（TMA-N）值、硫代巴比妥酸（TBA）、K值等指标对鲳鱼进行品质评价。实验结果表明:在贮藏前6d,臭氧冰和电解水冰对TMA-N影响并不显著（p>0.05）;贮藏后期,普通冰组、臭氧冰组的TVB-N值、p H、TMA-N值急剧上升,感官质量显著下降（p<0.05）。综合菌落总数、K值、感官指标、TVB-N、TMA-N等指标得出普通冰对鲳鱼的保鲜期为10d,相比于普通冰,浓度为0.89mg/kg的臭氧冰能够延长东海白鲳货架期1²d,而电解水冰能够延长东海白鲳货架期至19d。且电解水冰能够显著抑制菌落总数、延缓TVB-N值、K值等的增长,但对脂肪氧化有不利影响。臭氧冰和电解水冰能够有效抑制微生物的生长繁殖,显著保持鲳鱼品质,延长鲳鱼货架期。研究结果为鲳鱼品质保鲜提供理论参考。      

Effect of Okra Cell Wall and Polysaccharide on Physical Properties and Stability of Ice Cream

Stabilizers are used in ice cream to increase mix viscosity, promote smooth texture, and improve frozen stability. In this study, the effects of varying concentrations (0.00%, 0.15%, 0.30%, and 0.45%) of okra cell wall (OKW) and its corresponding water‐soluble polysaccharide (OKP) on the physical characteristics of ice cream were determined. Ice cream mix viscosity was measured as well as overrun, meltdown, and consumer acceptability. Ice recrystallization was determined after ice cream was subjected to temperature cycling in the range of ?10 to ?20 °C for 10 cycles. Mix viscosity increased significantly as the concentrations of OKW and OKP increased. The addition of either OKW or OKP at 0.15% to 0.45% significantly improved the melting resistance of ice cream. OKW and OKP at 0.15% did not affect sensory perception score for flavor, texture, and overall liking of the ice cream. OKW and OKP (0.15%) reduced ice crystal growth to 107% and 87%, respectively, as compared to 132% for the control (0.00%). Thus, our results suggested the potential use of OKW and OKP at 0.15% as a stabilizer to control ice cream quality and retard ice recrystallization. OKP, however, at 0.15% exhibited greater effect on viscosity increase and on ice recrystallization inhibition than OKW.     

Effect of calcium chloride addition on ice cream structure and quality

The influence of calcium fortification by the addition of calcium chloride on quality parameters of ice cream based on physical properties was investigated, as was the effect of κ-carrageenan at modifying the effects of this calcium fortification. Four ice cream mixes of conventional composition, with added κ-carrageenan (0 or 0.025%) and added calcium chloride (0 or 4.4 g L⁻¹ = 40 mM of added Ca²⁺), were prepared. Modulated temperature-differential scanning calorimetry was used to investigate the effect of calcium chloride on the nucleation temperature, enthalpy of melting, and freezing point depression. The protein composition of 15.4% (wt/wt) reconstituted skim milk powder solutions with or without 4.4 g L⁻¹ added CaCl₂ and in the supernatant after ultracentrifugation was determined. Fat particle size distributions in ice cream were characterized by light scattering. Ice crystal sizes before and after temperature cycling were determined by cold-stage light microscopy. The results demonstrated that the addition of calcium chloride led to a substantial increase in ice crystal sizes and in fat partial coalescence, which were exacerbated by the addition of κ-carrageenan. These results can be explained by the interaction between Ca²⁺ ions and casein micelles, rather than any effects on freezing point depression. The calcium ions led to a more compact micelle, less serum β-casein, and high fat destabilization, all of which would be expected to reduce macromolecular structure and volume occupancy in the unfrozen phase, which led to increased rates of ice recrystallization.     

Microbiological and biochemical quality of grouper (Epinephelus chlorostigma) stored in dry ice and water ice

The changes in the microbiological and biochemical quality of grouper (Epinephelus chlorostigma) stored in dry ice (solid carbon dioxide) were investigated. Fresh fish stored in dry ice at the ratio of 1:1 (wt/wt) were found to be organoleptically suitable for consumption when they were stored for 30 h without re‐icing. Fish stored in water ice (as control) at the ratio of 1:1 (wt/wt) and in a combination of dry ice and water ice at the ratio of 1:0.2:0.5 (wt/wt/wt) were acceptable up to 18 and 24 h, respectively. Total bacterial load ranged from 10⁵ to 10⁷ CFU g^?1, while total psychrophiles from 10³ to 10⁶ CFU g^?1. Total lactics were found in the levels of 10²–10⁴ CFU g^?1. Total volatile basic nitrogen contents were within the limit of acceptability in all the three treatments, whereas trimethylamine nitrogen content exceeded the limit (15 mg%) and hypoxanthine content was 11.11 mg (100 g)^?1 on the 30 h in grouper stored only in dry ice. Lowest temperature of ?5.8 °C was recorded in grouper stored only in dry ice. Hundred percent CO₂ environment within the package was found in grouper that were stored in dry ice and combination of dry ice and water ice.     

溶液相图在溶液浓缩及制冰方面的应用

阐述了溶液相图在稀溶液浓缩及制冰方面的应用，对冷冻浓缩和小冰晶的制取分别进行了详细论述。