全脂乳粉和脱脂乳粉在1kHz～10MHz下的介电特征研究

分别研究了各4种不同品种的全脂乳粉和脱脂乳粉在1kHz～10MHz波段的介电特性。结果发现:随着频率的增加,全脂乳粉和脱脂乳粉的ξ’和ξ″值呈单调递减趋势;全脂乳粉的ξ’和ξ″值都高于脱脂乳粉,相同类型乳粉各品种间的ξ’和ξ″差异不大;全脂乳粉的ξ″值在103～105Hz频率段减小趋势明显,且ξ″值的对数与频率的对数成线性反比关系,而脱脂乳粉无此规律;全脂乳粉和脱脂乳粉的穿透深度Dp随频率的提高而减小,两类乳粉的介电特性差异可能与它们各自的脂肪和乳糖含量有关。     

Spray drying of low‐phenylalanine skim milk: optimisation of process conditions for improving solubility and particle size

The optimisation of the spray drying process for low‐phenylalanine skim milk as a dietary supplement for phenylketonurics was studied. The effects of basic parameters including the inlet air temperature (100, 150 and 200 °C), feed flow rate (5, 10 and 15 mL min^?1) and air flow rate (400, 600 and 800 L h^?1) on the solubility and particle size of the low‐phenylalanine skim milk powder were determined using response surface methodology. The optimum conditions have been obtained with inlet air temperature of 133 °C, feed flow rate of 5 mL min^?1, and air flow rate of 800 L h^?1. With the optimum parameters, the predicted values for the solubility and mean diameter were 95.33% and 5.34 μm, respectively, and experimentally were 94.36 ± 1.62% and 5.50 ± 0.44 μm, respectively. The experimental and predictive values were closely related showing predictive accuracy of the models.     

Response surface optimisation of spray dryer operational parameters for low‐phenylalanine skim milk powder

The aim of this study was to optimise the spray‐drying process for low‐phenylalanine (low‐Phe) milk. Influence of inlet air temperature (100, 150 and 200 °C), feed flow rate (5, 10 and 15 mL min^?1) and air flow rate (400, 600 and 800 L h^?1) on the solubility, yield, water activity and moisture content (MC) of the milk powder were assessed using response surface methodology. The following optimum process parameters were determined: inlet air temperature of 160 °C, feed flow rate of 8 mL min^?1 and air flow rate of 400 L h^?1. The predicted values for the solubility, yield, water activity and MC were 98.77%, 88.08%, 0.263% and 5.48%, respectively. With the optimum parameters, the experimental values for the solubility, yield, water activity and MC were 97.56 ± 0.03%, 87.00 ± 0.10%, 0.26 ± 0.01% and 5.53 ± 0.08%, respectively. The similarity of the experimental results to the predicted values verified the models.     

The influence of temperature and pressure factors in supercritical fluid extraction for optimizing nonpolar lipid extraction from buttermilk powder

The milk fat globule membrane, readily available in buttermilk, contains complex lipids claimed to be beneficial to humans. Phospholipids, including sphingolipids, exhibit antioxidative, anticarcinogenic, and antiatherogenic properties and have essential roles in numerous cell functions. Microfiltration coupled with supercritical fluid extraction (SFE) may provide a method for removing triacylglycerols while concentrating these nutritionally valuable lipids into a novel ingredient. Therefore, SFE as a method for phospholipid concentration needs to be optimized for triacylglycerol removal in buttermilk. The SFE conditions were assessed using a general full factorial design; the experimental factors were pressure (15, 25, and 35 MPa) and temperature (40, 50, and 60°C). Particularly interesting is that only triacylglycerols were removed from buttermilk powder. Little to no protein loss or aggregation was observed compared with the untreated buttermilk powder. Calculated theoretical values showed a linear increase for lipid solubility as pressure, temperature, or both were increased; however, experimental values showed nonlinearity, as an effect of temperature. In addition, the particular SFE parameters of 35 MPa and 50°C displayed enhanced extraction efficiency (70% total lipid reduction).     

Original article: Supercritical CO2 extraction of soybean oil: process optimisation and triacylglycerol composition

Supercritical CO₂ extraction of soybean oil was performed. Response surface methodology was applied to evaluate the effects of pressure, temperature and extraction time on soybean oil yield. The analysis of variance showed that pressure and extraction time followed by the quadratic term of pressure and interaction between pressure and time had the significant effect on the oil yield. The maximum extraction yield (6.59/100 g soybeans) at constant CO₂ flow rate of 1.629 L per min was achieved at 50 °C, 300 bar and 4 h. The experimental values agreed well with those predicted by regression model. One‐stage diffusion model was successfully applied for modelling the kinetics of soybean oil. The main triacylglycerols of soybean oil were trilinolein, dilinoleoolein, dilinoleopalmitin and linoleooleopalmitin. Soybean oil extracted by supercritical CO₂ had higher levels of linoleic and linolenic acids and lower levels of palmitic and stearic acids compared to oil extracted by organic solvent.     

Short communication: Evaluation of supercritical fluid extraction aids for optimum extraction of nonpolar lipids from buttermilk powder

The milk fat globule membrane, present in buttermilk, contains complex lipids such as phospholipids. Microfiltration coupled with supercritical fluid extraction (SFE) may provide a method of enriching these nutritionally valuable lipids into a novel ingredient. Therefore, SFE as a method for phospholipid enrichment needs to be optimized for lipid removal effectiveness. The role of matrix additions to the buttermilk powder for extraction efficiency was evaluated. Diatomaceous earth (biosilicates), Teflon beads, and physical vibration were tested and shown to reduce total lipid by 86, 78, and 70%, respectively. Four consecutive treatments were shown to exhaust the system; however, similar extraction efficiencies were noted for 1 treatment with biosilicate addition, 2 treatments with physical vibration, or 3 treatments with added Teflon beads. The extracted lipid material consisted of the nonpolar fraction, and protein concentration was observed to increase slightly compared with the control. Although higher lipid extraction was achieved from the powder with addition of diatomaceous earth, a removable aid is ideal for an edible product.     

Coagulation and washing conditions for acid casein production from skim milk powder

Response surface methodology was used to study the production of acid casein from skim milk powder and to investigate the effects of pH, concentration and washing conditions (agitation, time, temperature and wash water ratio) on the end product. The washed curd was analysed for residual ash, minerals and lactose. The critical variables were found to be concentration and pH in relation to mineral content; and concentration and washing time for lactose. Surface response methodology provides a unique insight into the relationships between the variables related to the process and the results are used to explain the observations in terms of milk chemistry. The washing process was further evaluated in terms of the Murphree Stage Efficiency to elucidate the effect of the number of washing stages on residual whey components in the casein curd. This study contributes to understanding the extrusion process of skim milk powder which makes use of higher milk solids concentrations.     

Effect of supercritical CO2 extraction process parameters on oil yield and pigment content from by‐product hemp cake

This research gives an insight into the possibility of exploiting the one of the food industry's by‐products – pressed hemp cake. The complete recovery of oil from pressed hemp cake was achieved. Residual oil that remained in cake after pressing was extracted with supercritical CO₂ by applying different process parameters. Optimal extraction conditions were determined using response surface methodology. Total pigment contents of the oils obtained were determined. Extraction pressure had the most significant influence on yield and pigment content of extracted hemp cake oil. Depending on the pressure, the chlorophyll a content ranged from 101.11 to 378.28 mg kg^?1 and chlorophyll b from 65.14 to 189.78 mg kg^?1, while total carotene content was in the range from 33.58 to 132.67 mg kg^?1. The remaining oil in pressed hemp cake after supercritical CO₂ extraction was determined to be 0.56 ± 0.08% and the defatted cake was rich in proteins and fibre.     

牛奶粉上火机理研究

以添加了20%全脂奶粉的全价饲料为原料,研究了全脂奶粉对SD大鼠免疫器官指数、血液生化与血细胞指标及血清细胞因子的影响,探讨了饮食牛奶粉的上火机理.结果表明,在丙二醛、尿素氮质量分数及中间细胞数与中性粒细胞数上,全脂奶粉组均显著高于对照组;在超氧化物歧化酶质量分数及白细胞数与淋巴细胞数上,全脂奶粉组雄性大鼠显著高于对照组:在血清碱性磷酸酶质量分数上,全脂奶粉组显著低于对照组;在脾指数、胸腺指数、总蛋白、白蛋白、血糖、总胆固醇、天门冬氨酸氨基转移酶、丙氨酸氨基转移酶、Na+-K+-ATP酶、红细胞敷、血红蛋白、粒细胞百分比及白细胞介素-2等质量分数上,组间差异均不显著.提示肠道黏膜细胞与牛奶成分相作用可导致局部微炎症.     

Optimisation of spray drying process parameters for low‐fat honey‐based milk powder with antioxidant activity

The purpose of this study was to optimise process parameters to prepare spray‐dried honey‐based milk powder containing functional properties of honey. Experimental design with temperature (180 to 200 °C), honey concentration (5–15%) and feed flow rate (8–10 rpm) as independent variables was studied to investigate the effect on product responses. Results showed that increasing the temperature resulted in powder with lower moisture, bulk density, antioxidant activity, total phenolic contents, total flavonoid contents and higher water solubility index. Increasing feed flow rate resulted in higher moisture, bulk density, antioxidant activity, reduced water solubility index, total phenolic content and total flavonoid content, whereas increasing honey concentration resulted in increase in antioxidant activity, total phenolic content and total flavonoid content. The moisture content, bulk density, water solubility index, DPPH scavenging activity, total phenolic content and total flavonoid content were 3.27%, 0.44 g cc^?1, 96.67 g g^?1, 17.45%, 2.54 GAE g^?1 powder and 1.40 RE g^?1 powder, respectively.     

奶粉加速破坏性实验中质量参数的确定

在35℃和45℃的恒湿贮存条件下，考察了全脂和脱脂奶粉的脂肪氧化以及参与美拉德反应的蛋白质变性情况。全脂奶粉由于脂肪含量高，45℃下的硫代巴比妥酸反应物(TBARS)在10d以后便开始递增，明显早于30d才变化的反映美拉德反应的荧光强度，说明首先导致全脂奶粉品质变化的原因是脂肪氧化。在35℃和45℃下。脱脂奶粉荧光强度的增加都先于全脂奶粉，并且增加的幅度都很大，通过运用SDS-PAGE对蛋白质结构进行分析对照，荧光强度可以实时反映蛋白质的变性程度。     

超临界二氧化碳萃取玫瑰茄籽油的响应面优化

在单因素实验基础上,以萃取温度、萃取压力、萃取时间为影响因素,以萃取率为指标,运用响应面实验设计法对超临界CO2萃取玫瑰茄籽油工艺条件进行优化。结果表明,在萃取温度50℃、萃取压力28MPa、萃取时间110min的条件下,玫瑰茄籽油提取率可达22%以上。     

超临界二氧化碳萃取黄柏挥发油工艺

使用超临界二氧化碳技术对经过超声-微波处理过的黄柏中的挥发油进行萃取,并对萃取工艺进行响应面优化。在单因素预实验的基础上,以萃取压力、萃取温度、萃取时间为响应因素,黄柏挥发油的萃取量为响应值,根据中心组合(Box-Behnken)实验设计原理,采用三因素三水平的响应面分析法,确定各工艺条件对萃取量的影响,并用扫描电子显微镜(SEM)对萃取前、未超声-微波处理超临界萃取后及超声-微波处理超临界萃取后的黄柏进行比较观察,对萃取效果进行了微观解释。结果表明,经过超声-微波处理过的黄柏中的挥发油超临界二氧化碳萃取最佳工艺条件为:萃取压力为34MPa,萃取温度为41℃,萃取时间为66min,萃取率达6.03%。     

Physical properties of supercritical fluid extrusion products composed of milk protein concentrate with carbohydrates

Supercritical fluid extrusion (SCFX) is a novel process combining traditional extrusion and supercritical fluid technologies. The objective of this study was (i) to assess the effect of sugar, maltodextrin and cornstarch on the physical properties of milk protein concentrate (MPC) puffed extrudates and (ii) to compare the physical and textural properties of SCFX puffed MPC products with commercially puffed cereal products. Results showed that the nutritious MPC puffed products with carbohydrates can be made with textural properties (hardness, brittleness and crispness) resembling those of the commercial samples. The porosity of F2 (0.573) was assessed to the commercial product C1 (0.543) and C2 (0.595), the specific length of F3 (50.41) was assessed to C1 (45.51) and F4 (80.14) was assessed to C2 (78.12). The hardness of extrudate F3 (435.49 KPa) was assessed to C2 (482.7 KPa). The Young's modulus of F5 (87.03) was assessed to C2 (80.57). The starches affected the crispness of the extrudates, and sugar affected the hardness and brittleness significantly.     

Concentration of polar MFGM lipids from buttermilk by microfiltration and supercritical fluid extraction

Buttermilk contains the milk fat globule membrane (MFGM), a material that possesses many complex lipids that function as nutritionally valuable molecules. Milk-derived sphingolipids and phospholipids affect numerous cell functions, including regulating growth and development, molecular transport systems, stress responses, cross membrane trafficking, and absorption processes. We developed a two-step method to produce buttermilk derivative ingredients containing increased concentrations of the polar MFGM lipids by microfiltration and supercritical fluid extraction (SFE). These processes offer environmentally benign alternatives to conventional lipid fractionation methods that rely on toxic solvents. Firstly, using a ceramic tubular membrane with 0.8-micron pore size, we evaluated the cross flow microfiltration system that maximally concentrated the polar MFGM lipids using a 2n factorial design; the experimental factors were buttermilk source (fresh, or reconstituted from powder) and temperature (50 degrees C, and 4 degrees C). Secondly, a SFE process using supercritical carbon dioxide removed exclusively nonpolar lipid material from the microfiltered buttermilk product. Lipid analysis showed that after SFE, the product contained a significantly reduced concentration of nonpolar lipids, and a significantly increased concentration of polar lipids derived from the MFGM. Particle size analysis revealed an impact of SFE on the product structure. The efficiency of the SFE system using the microfiltration-processed powder was compared much more favorably to using buttermilk powder.     

超临界CO2萃取花椒籽油工艺的响应面优化

利用响应面法对花椒籽油的超临界CO2萃取工艺进行优化.在单因素试验基础上,以萃取压力、萃取温度、萃取时间为影响因素,花椒籽油提取率为响应值,根据中心组合(Box-Benhnken)试验设计原理采用3因素3水平的响应面分析法,确定各工艺条件对提取率的影响.结果表明,超临界CO2萃取花椒籽油的最佳工艺条件为:萃取压力37 MPa,萃取温度45℃,萃取时间65 min,花椒籽油提取率可达19.65%.     

Seasonal variation in the odour characteristics of whole milk powder

Seasonal changes in whole milk powder odour characteristics were monitored using SPME-GC and E-nose methodologies. ANOVA showed a significant effect of the season on dimethyl sulphide, n-pentanal, n-hexanal, and butyric acid. Whole milk powder manufactured in summer season had significantly (p < 0.05) higher levels of n-hexanal, n-pentanal and dimethyl sulphide as compared to autumn and winter seasons. On the other hand, butyric acid showed significant differences (p < 0.05) among autumn and spring. Applying linear discriminant analysis, seasonal variations in the odour profiles assessed by electronic nose were observed. A better classification outcome was obtained when volatile compounds and electronic nose data were analysed together, obtaining a success rate of 89.5% and 70.7% of the original cases and after cross-validation respectively. As in other application reported in the literature, E-nose approach represents an alternative technique to traditional methods of odour measurement.