凝固型芝士风味发酵乳的制备

以生牛乳、白糖以及芝士酱为主要原料,以酸度和感官评价为检测指标,通过单因素试验和正交试验确定凝固型芝士风味发酵乳的最佳发酵工艺条件。结果表明,凝固型芝士风味发酵乳的最佳发酵工艺条件为白砂糖7.5%、芝士酱0.9%、发酵温度43 ℃,发酵时间5.5 h。在此优化条件下,成品感官评分为91分,酸度为78.9 °T,产品组织细腻均匀,无乳清水析出,酸甜适中,口感嫩滑,且具有芝士酱特有的风味。     

自然发酵酸笋中乳酸菌的筛选鉴定及益生特性研究

为筛选自然发酵酸笋中的益生乳酸菌,采用MRS培养基分离,经生理生化实验及16S rDNA序列分析鉴定,通过溶血实验评价安全性以及耐酸耐胆盐实验评价耐受性,并测定乳酸菌体外抗氧化性。结果表明,共分离到69株乳酸菌,隶属于2个科3个属,分别为乳杆菌属（Lactobacillus）、片球菌属（Pediococcus）、链球菌属（Streptococcus）,均为γ-溶血的安全菌株,且均对0.3%胆盐具有良好耐受性,其中41株乳酸菌耐pH 2.0酸性条件,从中优选出的17株乳酸菌对人工胃肠液均有良好耐受性。4株短乳杆菌（Z1-02、ZR2-14、ZR2-12、ZR2-22）和2株消化乳杆菌（ZR1-02、ZR1-05）的1,1-二苯基-2-三硝基苯肼（DPPH）自由基清除率、2,2'-联氮-双-3-乙基苯并噻唑啉-6-磺酸（ABTS）自由基清除率、还原能力均分别＞62%、79%、0.393,其中乳杆菌Z1-02的综合抗氧化能力最强,这6株乳酸菌具备优良的益生性能和体外抗氧化活性。     

Chemical composition,adulteration, total microbial load,and heavy metal in raw milk samples collected from dairy farms and urban areas in Lahore District,Pakistan

The present study evaluated raw milk samples from dairy farms and urban areas in Lahore District, Pakistan, for the measurement of chemical composition, presence of adulterants, total microbial, and heavy metals loads. Measurements of chemical composition and physicochemical properties of the raw milk samples collected from urban areas showed the following mean values of 2.76 ± 0.29, 2.62 ± 0.18, 1.27 ± 0.08, 7.13 ± 0.30, 6.46 ± 0.26, and 0.47 ± 0.02 for lactose, fat, protein, total solids, pH, and ash, respectively, while milk samples collected from dairy farms achieved the mean values of 4.82 ± 0.32, 5.02 ± 0.39, 3.36 ± 0.18, 13.19 ± 0.66, 6.67 ± 0.27, and 0.75 ± 0.05 for lactose, fat, protein, total solids, pH, and ash, respectively. Mean values of total plate count were 5.21 ± 0.28 CFU/ml for urban areas raw milk samples and 4.67 ± 0.27 CFU/ml for the dairy farm milk samples. Heavy metal mean concentrations for Pb, Cd, Cu, Zn, and Ni in urban areas milk samples from milk shop were 0.024 ± 0.005, 0.021 ± 0.006, 1.22 ± 0.25, 2.42 ± 0.57, and 0.044 ± 0.006 ppm, respectively. Conclusively, strategies should be adopted in order to prevent the heavy metal contamination in milk to further minimizes the health risks associated with heavy metal consumption.     

植物油脂替代动物油脂 在再制奶油干酪中的应用

以奶油干酪为基料,研究不同植物油脂替代动物油脂在再制奶油干酪中的应用。测定干酪样品的质构、色度、油脂析出性、融化性及感官评定,并进行比较分析。实验结果表明,添加橄榄油和小麦胚芽油的干酪硬度和涂抹性与对照组相近(P>0.05);添加橄榄油、小麦胚芽油、油茶籽油和米糠油的干酪粘聚力与对照组接近,减少了15.23%~26.68%;添加橄榄油和油茶籽油的干酪粘合性与对照组相差19.68%、33.16%,差异显著(P<0.05)。添加油茶籽油、橄榄油、米糠油、小麦胚芽油和亚麻籽油的干酪色度与对照组十分相近(P>0.05)。在油脂析出性上,添加玉米油、米糠油、橄榄油、油茶籽油和南瓜籽油的实验组品质均得到了改善。添加橄榄油、亚麻籽油的样品组在融化性能上与对照组差异不显著(P>0.05),仅减少了1.15%和1.85%。添加油茶籽油、橄榄油、小麦胚芽油的样品组受到认可,得分高于对照组。综上,橄榄油组与对照组在各项指标上相似度最高,是较好的替代油脂。     

Enhancing the potential use of microparticulate insecticides through removal of particles from raw grain

The current study presents the design and evaluation of a laboratory device combining mechanical motion of wheat grain and turbulent air streaming inside a positive pneumatic conveyor system. The device recovers microparticulate nano-engineered alumina insecticide powders (NAIP) from treated grain. The particle removal efficiency of the conveying system was experimentally quantified by using a laboratory prototype assembled by attaching an electrostatic filter (EF) to the conveyors exhaust. Then, the NAIP particles detached from the grain inside the conveyor were drawn by the conveyors’ exhaust air stream into the EF, where particles bound to the electrodes due to electric charge differences. The NAIP particle load bound to the EF electrodes was removed and weighed to determine the efficiency of the wheat grain cleaning process. Our experimental results, under laboratory conditions, show that the recovery efficiency of the prototype averaged 98.0% (±1.4). Thus, the present study provides an innovative strategy to remove NAIP insecticide particles after storage, once their role as insecticide in stored grain has been fulfilled. This technology provides advancement in grain technology allowing the possibility to provide insecticide-free grain to the food market.     

Radio frequency heating against Sitophilus zeamais Motschulsky in white maize

Radio frequency treatments were evaluated for the control of Sitophilus zeamais Motschulsky in white maize, and their effects on physiological and biochemical properties were evaluated. A 12 kW, 27.12 MHz radio frequency machine was used with an electrode gap of 20 cm; batches of 10 and 20 kg of white maize (11.8% moisture content, w.b.) were treated. Radio frequency heating treatments at 50 °C for 3 min or 60 °C in white maize were effective to achieve 100% mortality of Sitophilus zeamais 4th instar larvae. Significant changes were observed in the moisture content, water activity and color in the corn kernels after the treatments (P < 0.05); however, they were within the range established by the Mexican Standard. As an advantage, the viability and germination of the grain were not affected by the treatments (P > 0.05). Radio frequency has potential to be a postharvest treatment against this pest without damage to white maize.     

副干酪乳杆菌K56调节肠道菌群及润肠通便功能研究

目的:参考保健食品检验与技术评价规范(2003版)中关于调节肠道菌群及通便功能动物实验评价方法评价副干酪乳杆菌调节肠道菌群及润肠通便功能。方法:分别以0.000867、0.00867、0.0867、0.867、8.67 mg/kg灌胃给予副干酪乳杆菌K56菌株(实验室检测菌株规格为1.5×1011 CFU/g),检测小鼠干预14 d前后双歧杆菌、乳杆菌、肠杆菌、肠球菌、产气荚膜梭菌含量,并测定干预30 d后小肠墨汁推进率、首粒黑便时间、排黑便粒数及重量,评价副干酪乳杆菌对小鼠肠道菌群及排便的影响。结果:干预14 d前后比较,各组小鼠粪便双歧杆菌、乳杆菌、产气荚膜梭菌均显著增加(P<0.05),而肠杆菌和肠球菌无显著变化(P>0.05);与对照组比较,以0.00867、0.0867、0.867 mg/kg剂量的K56干预后,小鼠肠道内双歧杆菌及乳杆菌数量显著增加(P<0.05),0.000867、0.00867、0.867 mg/kg剂量的K56干预后产气荚膜梭菌含量显著降低(P<0.05);与模型组比较,0.00867、0.867、8.67 mg/kg剂量组干预小鼠墨汁推进率显著增高(P<0.05),0.0867、0.867 mg/kg剂量组小鼠排黑便粒数与重量显著增加(P<0.05),但各剂量组对小鼠首粒黑便时间与模型对照组无显著性差异(P>0.05)。结论:副干酪乳杆菌K56菌株具有调节肠道菌群和润肠通便的作用,调节肠道菌群最佳剂量为0.0867 mg/kg(对应人体剂量1.0×108 CFU/d),润肠通便最低有效剂量为0.867 mg/kg(对应人体剂量为1.0×109 CFU/d)。     

尿素包合法富集驼峰油中不饱和脂肪酸的工艺优化

以精炼驼峰油混合脂肪酸(饱和脂肪酸54. 024 3%,单不饱和脂肪酸34. 645 7%,多不饱和脂肪酸4. 645 3%)为原料,在单因素试验基础上,采用响应面法优化尿素包合法富集其不饱和脂肪酸工艺。结果表明:尿素包合法富集驼峰油中不饱和脂肪酸的最佳工艺条件为尿素质量与95%乙醇体积比3∶8、尿素与混合脂肪酸质量比3. 315∶1、包合温度-2. 37℃、包合时间18. 13 h,在此条件下产物碘值(I)为125. 73 g/100 g,产物中饱和脂肪酸含量为7. 802 5%,单不饱和脂肪酸含量为58. 175 6%,多不饱和脂肪酸含量为17. 322 2%。包合后产物为淡黄色黏稠液态,不饱和脂肪酸含量约为75%。     

Novel cultures for cheese improvement

Developments in the molecular genetics of food bacteria have now made possible the construction of designer cultures with the potential to improve important characteristics of cheese including production efficiency, safety and health properties. Such advances are set to expand the range and understanding of both starter and probiotic cultures, especially at a time when the total genomes of many strains are being determined and will become available. To illustrate the types of improvements which such technologies can bring, examples are given such as development of bacteriophage resistant starters and bacteriocin-producing starters with the potential to control adventitious cheese flora.     

Influence of feed properties on membrane fouling in crossflow microfiltration of particulate suspensions

The effects of the feed concentration (C_feed) and particle size distribution (PSD) on the crossflow microfiltration (CFMF) of suspensions containing lactalbumin particles were investigated. Experiments were carried out in constant transmembrane pressure (TMP) mode using tubular ceramic membrane modules. All the important parameters: permeate flux, internal and surface fouling, cake mass, height, porosity, and PSD were estimated. The steady-state flux (J_ss) decreased, and internal as well surface fouling and cake mass and height all increased with an increase in C_feed from 0.65 to 2.5 gL⁻¹. This was due to the availability of more particles to foul the membrane at higher C_feed. However, above 2.5 gL⁻¹ there was no significant effect of C_feed on any of these parameters. The overall observed behaviour is attributed to steady-state membrane fouling resulting from the availability of sufficient particles for maximum possible deposition under the experimental conditions reached at 2.5 gL⁻¹. The larger the feed particles, the higher was the J_ss. However, the cake mass, height and porosity were not affected by the feed PSD. Significantly, addition of larger feed particles at the steady state increased the flux by about 6%. This behaviour is attributed to the scouring effect of the large particles on the cake surface. There is scope for looking at the possibility of using the scouring effect of large particles to improve the CFMF process performance.