利用γ-谷维素与β-谷甾醇制备葵花油凝胶研究

以一级压榨葵花籽油为原料,添加一定浓度的γ–谷维素与β–谷甾醇混合物制备出葵花油凝胶,探究不同制备工艺条件对葵花油凝胶硬度及微观结构的影响。在单因素试验的基础上,通过正交试验确定了6%γ–谷维素与β–谷甾醇混合物添加量葵花油凝胶的最优制备条件。试验表明,影响葵花油凝胶硬度因素的主次顺序为:冷却温度>γ–谷维素:β–谷甾醇添加比例>加热时间>加热温度;6%γ–谷维素与β–谷甾混合物醇添加量葵花油凝胶的最优制备工艺为:加热温度140℃,加热时间50 min,冷却温度5℃,γ–谷维素∶β–谷甾醇添加质量比例60∶40。在最优工艺条件下,6%γ–谷维素与β–谷甾醇添加量葵花油凝胶硬度为479.61±9.18 g。     

Impact of shelf life on content of primary and secondary metabolites in apple (Malus domestica Borkh.)

In this study, we evaluated the changes in apple fruit quality during shelf life. After a month of cold storage, apples of cultivars "Jonagold" and "Golden Delicious" were exposed to ambient temperatures for 21 d, with subsequent sampling every 3 or 4 d. Fruit firmness, changes in amounts of sugars, malic acid, and phenolics were observed during shelf life. Chemical analyses were done with HPLC-PDA system. An interchange between various sugars was noticed, but in general, the sum of sugars remained at the same level. The content of malic acid remained stable or dropped, resulting in sweeter fruit. Levels of phenolics were more constant in the pulp of both cultivars analyzed, while in the peel, the changes were more pronounced. In the pulp, a peak in the content of hydroxycinnamic acids and flavanols was noticed on the 2nd or 3rd sampling and afterwards, the amounts remained constant. In the peel an initial decrease of all analyzed phenolic groups was observed in both cultivars, however it was more pronounced in "Jonagold." It can be concluded that changes in primary and secondary metabolites are not the main reason for the lower quality of fruit exposed to ambient temperatures. On the other hand, fruit firmness might be the limiting factor for shelf life duration.     

Optimization of baking parameters of part-baked and rebaked Irish brown soda bread by evaluation of some quality characteristics

Summary  Part-baked Irish brown soda bread loaves with bicarbonate levels from 0 to 2.8 % were baked, packed and stored for up to 11 days at 5 C then second-baked at 180 or 200 C for various times to give an oven-fresh end product. The quality of the rebaked bread was dependent on characteristics of the part-baked bread, its storage conditions and the processing parameters of the second baking phase. Quality parameters evaluated were bread volume yield, crumb and crust firmness, moisture content and colour. Staling of the part-baked bread during storage at 5 C and the reversion of this process at 59 C was investigated with regard to rebaking time and temperature. Rebaking conditions were optimized by evaluating the core temperature increase in the centre of the bread. Immediately after the second baking phase a post-baking temperature increase was measured which allowed reduction of the in-oven rebaking time. The data were modelled mathematically using least squares analyses.     

可见/近红外漫反射光谱无损检测甜柿果实硬度

该研究的目的是建立可见/近红外漫反射光谱无损检测甜柿果实硬度的数学模型,评价可见/近红外漫反射光谱无损检测甜柿果实硬度的应用价值。果实硬度采用果皮脆性、果皮强度和果肉平均硬度作为评价指标。在可见/近红外光谱区域(400～2 500 nm),采用改进偏最小二乘法,对比分析了不同导数处理、不同散射及标准化处理的甜柿果实硬度定标模型。结果表明,对于果皮强度和果皮脆性,采用最小偏二乘法、一阶导数处理和标准多元离散校正处理建立的定标模型预测效果较好,RP2分别为0.858和0.862,SEP分别为0.094和0.157,RPD分别为2.47和2.63。对于果肉平均硬度,采用改进偏最小二乘法、一阶导数处理和标准正常化和去散射处理建立的定标模型预测效果较好,RP2为0.82,SEP为0.063,RPD为2.35。因此,可见/近红外漫反射光谱无损检测技术可用于甜柿果实硬度的无损检测。     

Gelation Property of Alcohol-Extracted Soy Protein Isolate and Effects of Various Reagents on the Firmness of Heat-Induced Gels

Gelation property, thermal property, protein subunits distribution, and molecular forces involved in gelation of alcohol-extracted soy protein isolate were investigated using texture analyzer, differential scanning calorimeter, sodium dodecyl sulfate polyacrylamide gel electrophoresis, and various reagents. Results showed that salts and pH played important roles in gel firmness, and a power law relationship between gel firmness and protein concentration was observed. The effects of various reagents revealed that disulfide bonds play a major role in soy protein gel formation, while the involvement of electrostatic interactions, hydrogen bonds, and/or hydrophobic interactions also occurred in gel networks. Thermal analysis indicated that both alcohol-extracted soy protein isolate and commercial soy protein isolate (isoelectric precipitation) have undergone serious denaturation, while the gel firmness of alcohol-extracted soy protein isolate was significantly greater than that of commercial soy protein isolate. Sodium dodecyl sulfate polyacrylamide gel electrophoresis image showed that there was almost no difference for protein subunits among alcohol-extracted soy protein isolate, commercial soy protein isolate, and soy powder. Hence, as an alternative environmental friendly extraction method, alcohol-extraction of soy protein isolate has a great prospect to replace presently applied isoelectric precipitation method.     

Evaluation of apple texture with contact acoustic emission detector: A study on performance of calibration models

Performance of calibration models for evaluation of apples sensory texture with contact acoustic emission detector (CAED) was studied. For model evaluation and testing, 2500 apples of 19 cultivars were harvested over two seasons. Apples were stored at normal atmosphere (NA), controlled atmosphere (CA) for different periods or were treated with 1-methylcyclopropene (1-MCP) in order to obtain a high variability of texture and fruit maturity. Apples were tested simultaneously in two distinct laboratories. The models were created and validated on averaged values from 10 fruits using simple linear regression, multiple linear regression (MLR) and principal component regression (PCR). Performance statistics of the models were expressed in terms of determination coefficient (R²), root mean square errors of cross validation (RMSECV) or prediction (RMSEP) and ratio of prediction to deviation (RPD). Firmness and total acoustic emission counts were predictors of sensory texture in the models. MLR and PCR models show better performance for prediction of sensory data than simple linear regression models however PCR models show the best results among models tested in this study. Common PCR models for several cultivars allow for successful prediction of hardness (RPD > 2.0), crispness and overall texture (1.5 < RPD < 2.0). The single-cultivar PCR models, constructed on data sets containing 26-39 averaged values, reveal significantly better performance (RPD > 2.0 for most of the cases) than the common PCR models for many varieties.     

基于高光谱技术苹果硬度快速无损检测方法的建立

目的 利用高光谱技术建立苹果内部品质无损检测的方法。方法 将高光谱图像的光谱信息和空间信息结合, 采用洛伦兹函数对苹果高光谱的空间散射曲线进行拟合, 提取拟合曲线的相关参数, 利用拟合参数对苹果硬度进行建模分析。结果 拟合曲线与原散射曲线的相关系数R达到0.99以上。分析比较多种统计建模方法对不同拟合参数的建模效果, 结果表明: 在524~1016 nm波段范围内, 利用偏最小二乘法(partial least squares, PLS)对拟合曲线的峰值建立硬度的预测模型, 校正集预测值与标准值的相关系数Rc=0.89, 校正集标准误差SEC=0.71×105 Pa, 验证集预测值与标准值的相关系数Rv=0.88, 验证集标准误差SEV=0.88×105 Pa。结论 利用高光谱散射成像技术, 采用偏最小二乘的方法对拟合峰值建模, 可以实现苹果硬度的快速无损检测。     

高光谱成像的红提总酸与硬度的预测及其分布可视化

利用高光谱成像技术实现对红提总酸和硬度无损检测和分布可视化。首先,利用高光谱采集生长期360个红提样本在波段450～1 000 nm的高光谱图像信息后用化学方法测定对应样本的总酸,用质构仪测定硬度。采用KS(Kennard-Stone)算法将总样本按照3∶1的比例划分为训练集（270个样本）和测试集（90个样本）。对红提原始光谱数据分别利用标准正态变量变换（standard normal variate transformation,SNV）、卷积平滑（Savitzky-Golay,SG）处理法、多元散射校正（multivariate scatter correction,MSC）、归一化等光谱预处理方法处理,确定最优光谱预处理方法。然后,分别采用一次降维（竞争性自适应重加权算法（competitive adaptive reweighted sampling,CARS）、连续投影算法（successive projections algorithm,SPA）、遗传算法（genetic algorithm,GA）、无信息变量消除法（uninformative variable elim...     

Influence of variation in calcium content on casein micelle stability and techno-functional properties of buffalo milk

Changes in techno-functional properties of buffalo milk were evaluated due to variation in calcium content. Decalcification resulted in significant variation in ζ-potential, casein size, colour and η_app. However, calcium addition only influenced ζ-potential of milk. In case of acid gelation, the time and temperature required for coagulation decreased significantly for both calcium-depleted and -added milks. However, during chymosin gelation, only 20%–30% of calcium-depleted milk coagulated with an increased clotting time. Furthermore, calcium addition increased firmness, consistency and cohesiveness of both chymosin and acid-induced gelation.