乳粉中的玻璃化相变及对乳粉品质的影响

在无定形聚合物玻璃化相变理论的基础上,介绍了乳粉中乳糖的玻璃相变及测定方法,讨论了玻璃化相变的影响因素以及对乳粉品质的影响。     

牛奶保鲜剂对牛乳成分及乳粉品质影响的研究

根据国外资料报道和我们试验结果证明,活化乳中过氧化物酶体系,可以抑制和拮抗细菌生长和繁殖,从而延长鲜牛奶的保鲜期。该法对发展中国家及缺少生奶冷却设备的偏僻地区,具有重要的意义。鲜奶之所以在最初挤出的几小时内不变质,是因为鲜奶本身含有乳过氧化物酶抗菌体系,简称 LP 体系。该体系由乳过氧化物酶(LP),硫氰酸盐(SCN~-),过氧化氢(H_2O_2)     

淀粉的玻璃化转变及其对食品品质的影响

本文在有关玻璃态和玻璃化转变理论的基础上,综述了淀粉玻璃化转变的分析方法、性质以及对食品品质的影响,并对今后的研究方向作了展望。     

玻璃化转变与重结晶对冰淇淋品质的影响

本文应用玻璃化理论解释了影响冰淇淋中晶体大小的因素及防止冰淇淋重结晶的措施     

玻璃化转化对食品加工和品质的影响

在有关玻璃态和玻璃化转变理论的基础上,综述了玻璃化转变对干燥、冷冻、焙烧、糖果及挤压等食品的加工与品质的影响。     

淀粉玻璃化转变及其对食品品质影响

淀粉是以谷物为原料的食品主要成分,而淀粉玻璃化转变对食品品质,特别对质构具有显著影响。该文在有关玻璃态和玻璃化转变理论基础上,综述淀粉玻璃化转变分析方法、影响因素及其对食品品质影响,并对今后研究方向进行展望。     

玻璃化转变对食品加工和品质的影响

在有关玻璃态和玻璃化转变理论的基础上 ,综述了玻璃化转变对干燥、冷冻、焙烤、糖果及挤压等食品的加工与品质的影响     

颗粒度对乳粉品质稳定性的影响

目的通过建立乳粉感官评价体系和理化指标评价体系两个评价方法来反映乳粉的品质稳定性,从而综合评定乳粉颗粒度对乳粉品质稳定性的影响。方法乳粉的感官主要从乳粉的气味、冲调液的滋味和气味方面进行感官评定。乳粉的理化评价体系主要考察乳粉的表面油含量、酸值及过氧化值。结合感官评价体系和理化评价体系的结果,调整乳粉生产工艺,选择最佳的乳粉颗粒度。结果乳粉的颗粒大小、脂肪的存在形态影响乳粉的品质稳定性。结果表明乳粉颗粒越大,其品质稳定性相对越高。结论综合感官及理化指标,颗粒度与乳粉的感官及品质稳定性呈正相关:乳粉的颗粒越大,感官得分越高,理化指标(表面油含量、酸值及过氧化值)越低,乳粉的品质稳定性越好。     

脱脂乳粉非酶褐变影响因素的实验研究

在食品、饮料、营养品、医药等行业广泛涉及非晶态粉体产品,这些粉体产品的非酶褐变,会严重影响产品质量。本文对脱脂乳粉的非酶褐变特性进行了实验研究;考查了水分活度、贮藏温度、储藏时间和玻璃化转变温度等参数对脱脂乳粉非酶褐变的影响。结果表明:随着水分活度、贮藏温度、贮藏时间以及贮藏温度T与脱脂乳粉的玻璃化转变温度Tg间的差值(T-Tg)的增加,脱脂乳粉非酶褐变指数显著增大;脱脂乳粉应在较低水分活度(例如0.3以下)和较低温度(例如40℃以下)下贮藏,以延长其货架寿命。     

冷冻贮藏对喷雾干燥羊乳粉品质特性的影响

本研究中对新鲜羊乳、低温冷冻（-16~-18 ℃）和超低温冷冻（-76~-80 ℃）贮藏3个月的常温解冻（20~25 ℃）羊乳进行喷雾干燥,制备了鲜羊乳粉、低温冷冻常温解冻（CFHT）羊乳粉和超低温冷冻常温解冻（UFHT）羊乳粉,对其品质进行比较分析。结果表明：喷雾干燥羊乳粉的水分质量分数符合国家标准,水分活度（A_w）均小于0.2,总色差（ΔE）均小于0.3,具有良好的贮藏特性;3组羊乳粉复水后多分散性指数（PDI）均小于0.3;激光共聚焦显微镜（CLMS）图像显示3组羊乳粉复水后组间脂肪球与蛋白质颗粒无明显差异。相比于鲜羊乳粉,CFHT和UFHT羊乳粉的脂肪损失较严重（P<0.05）,蛋白质和乳糖质量分数损失10%~19%（P<0.05）;而UFHT羊乳粉的蛋白质和乳糖高于CFHT羊乳粉,水分质量分数和A_w低于CFHT羊乳粉。因此,冷冻贮藏可用于喷雾干燥羊乳粉的制备,且UFHT羊乳粉的品质优于CFHT羊乳粉。     

Water sorption and glass transition properties of spray dried lactose hydrolysed skim milk powder

The moisture sorption behaviour and glass transition temperature of spray dried skim milk powder with hydrolysed lactose (SMPHL) were determined. Spray drying of skim milk with hydrolysed lactose resulted in very low cyclone recovery of 25% and a large amount of powder remained stuck inside the spray dryer. The equilibrium moisture content of SMPHL was lower than that of lactose for each range of water activity when humidified for 21 days at 23 °C using saturated salt solutions. Unlike lactose, SMPHL did not lose water when the water activity exceeded 0.432 and no crystallization was noticed at water activity ?0.753. The sorption isotherm data for SMPHL fitted well with the BET and GAB models with monolayer moisture contents of 7.55 and 8.27 g/100 g, respectively. The glass transition temperature of anhydrous SMPHL was 49 °C. The critical water activity and moisture content for SMPHL were 0.15 and 2.4 g/100 g dry solid, respectively. The low critical values indicated hydrolysis of lactose necessities maintenance of very low moisture of powder for its long-term stability.     

Effect of protein concentration on the surface composition,water sorption and glass transition temperature of spray-dried skim milk powders

The effects of dilution of protein content in skim milk (34–8.5% protein content), by lactose addition, on the surface composition, water sorption property and glass transition temperatures of spray-dried powders were investigated. The X-ray photoelectron spectroscopy (XPS) study of spray-dried powders showed preferential migration of proteins toward the surface of the milk particles whereas the lactose remained in the bulk. Sorption studies showed that the lower protein concentration in milk powders is linked to an increased water adsorption property and lowering of water activity (a_w) for lactose crystallization. Analysis of glass transition temperature (T_g) of the powders sorbed at different humidities showed no distinct change in T_g values, indicating the dominant effect of lactose on the glass transition temperature of all the powders.     

奶粉流动性测试方法

目的测试粉体流动性,对比测试手段,分析各参数对安全生产和质量控制的实际指导意义。方法采用卡尔(Carr)指数法和Jenike法对市售奶粉进行粉体流动性测试。结果 Carr指数法从粉体的休止角(自然坡度角)、压缩度、板勺角(平板角)和凝集度对奶粉的流动性进行表征,Jenike法从粉体流动函数、壁面摩擦、松装密度、时间固结、拱架、鼠孔、料斗半角等方面对奶粉的流动性进行表征。结论 Carr指数法测试手段比较简单,但具有一定的经验性,只能用以表示和比较粉体物料的相对流动性,其数据的重复性和可靠性低于Jnike方法。Jenike法虽然涉及的参数多,计算量大,但其对安全生产和质量控制的实际指导意义优于Carr指数法。     

奶粉中DHA测定方法的探讨

介绍了DHA的生理功能及奶粉中DHA的测定方法。结合实际工作经验．探讨了影响DHA测定结果的因素，并对建立奶粉中DHA测定方法提出了建议。     

Storage stability of coconut milk powder

Spray-dried coconut milk powder prepared with additions of skim milk and dextrin was stored in packages for 6 months at room temperature (30°C and 80% RH). The packaging materials used were aluminum laminate (vacuum and air packed) and polypropylene. The sorption isotherm of the powder showed that the monolayer of water molecules was complete when the relative humidity was 27% which corresponded to a moisture content of 5%. Measurements of water activity, moisture content, peroxide value and solubility index indicated that lipid oxidation is the limiting factor in the stability of the powder. Its maximum shelf-life was 4 months when air or vacuum packaged in aluminum laminates and 1 1/2 months in polypropylene.     

乳粉中矿物质检测稳定性分析研究

目的对乳粉中矿物质元素检测的稳定性进行分析研究。方法依据国标方法对GB 10765-2010中必需要求的12种矿物质元素进行检测,在同一实验室对同一乳粉中的矿物质元素进行重复检测确定产品的稳定性;在不同实验室对同一乳粉中的矿物质元素进行检测,发现实验室检测稳定性的差异。结果发现同一实验室对同一批次乳粉中矿物质元素检测的稳定性较好,不同实验室间矿物质元素检测稳定性相对较差。结论统一实验室检测方法,提升实验室检测水平,是确保检测稳定性的前提,有利于为企业生产时提供准确的检测数据,对制定产品配方具有重要指导意义。     

乳粉中维生素检测稳定性分析研究

目的对乳粉中维生素检测的稳定性进行分析研究。方法依据国标方法对GB 10765-2010中必需要求的13种维生素进行检测,在同一实验室对同一乳粉中的维生素进行重复检测确定产品的合格性;在不同实验室对同一乳粉中的维生素进行检测,发现实验室检测稳定性的差异。结果同一实验室对同一批次乳粉中维生素检测的稳定性较好,不同实验室间维生素稳定性相对较差。结论统一实验室检测方法,提升实验室检测水平,尽可能开发仪器检测方法,是确保检测稳定性的前提,有利于为企业生产时提供准确的检测数据,对制定产品配方具有重要指导意义。     

Oxidation stability of the lipid fraction in milk powder formulas

The purpose of this study was to predict the shelf life of distinct milk powder formulas by measuring hydroperoxides, headspace volatile compounds (propanal, pentanal and hexanal), fatty acid content, and sensory quality. The oxidation stability of three formulas was followed over 15 months of storage at 25 and 37 °C. These formulas were a non-supplemented formula (NSF), and two formulas supplemented with n − 3 and n − 6 long-chain polyunsaturated fatty acids, a formula with 0.83 and 0.47% (SFA), and one with 27.8 and 3.51% of n − 3 and n − 6 long-chain polyunsaturated fatty acids (SFB), respectively. Relative stability decreased in the order NSF at 25 °C > SFA at 25 °C ? SFA at 37 °C ? SFB at 25 °C > SFB at 37 °C. Therefore, we conclude that the polyunsaturated fatty acid content, storage temperature and storage time are very important factors for determining the oxidation stability.