桑椹渣去糖工艺研究

以桑椹酿酒后果渣为原料,使用糖化酶对桑椹果渣进行去糖,通过单因素及正交试验进行桑椹果渣中不溶性膳食纤维提取前去糖工艺条件优化。结果表明,去糖最佳工艺条件为糖化酶2 g/kg、酶解时间90 min、酶解温度63 ℃、pH值为4。     

碱法提取桑椹果渣中不溶性膳食纤维工艺研究

以酿酒后桑椹果渣为原料,使用糖化酶对桑椹果渣进行去糖、碱提,通过单因素及正交试验进行桑椹果渣中不溶性膳食纤维的提取工艺条件优化,并对提取物进行理化特性研究。结果表明,桑椹果渣中不溶性膳食纤维最佳提取条件为：碱质量分数1.5%、碱提时间2.0 h、碱提温度60 ℃、料液比1∶12（g∶mL）,在此优化条件下,不溶性膳食纤维提取率达28.77%,其吸水膨胀性为4.81 mL/g、持水性5.23 g/g、持油性1.6 g/g。     

Influence of carrot fibre powder addition on rheological,microstructure and sensory characteristics of stirred-type yogurt

The incorporation of 1% (E1) and 2% (E2) of the carrot fibre powder obtained from carrot discards to yogurts was studied. The effect of the fibre addition on the physicochemical parameters, water-holding capacity (WHC), microbial counts, rheological, microstructure and sensory characteristics of yogurts was studied in comparison with control yogurt without fibre addition (C). Titratable acidity, global composition and microbial counts showed a similar trend among yogurts. Fibre particles seemed to change the organisation of protein aggregates of the gel network. An open structure with bigger aggregates was observed in E1 and E2 yogurts, while the microstructure appeared more homogenous and without granules in C. However, carrot fibre increased the WHC of yogurt. All the yogurt samples exhibited shear-thinning behaviour and no differences were found in the rheological parameters, excepting for E2 that presented a decrease in apparent viscosity at 200 s^-1 compared with C and E1 samples. Trained sensory panel (12 members) indicated an increase in brownish colour, strange flavour, grittiness and aftertaste and a decrease in overall appearance, odour, sweetness and creaminess in yogurts enriched in fibre. In order to mask these negative characteristics, E1 formulation was produced in the same way but strawberry flavour and colour were added. A consumer test (101 volunteers), purchase intention and a Check All That Apply (CATA) questionnaires were carried out. Flavoured and coloured E1 yogurt was pleasant for consumers, since 93% of the consumers selected positive degrees of acceptability and 68% of them manifested that they are willing to consume the product. Therefore, the addition of carrot fibre powder in yogurts could be an alternative to incorporate dietary fibres into dairy foods.     

Effect of calcium on the physical properties of stirred probiotic yogurt

The effect of calcium on the viscosity, firmness, and smoothness, as determined by extent of nodulation, of stirred probiotic yogurt produced by bacterial fermentation was investigated. Standardized milk for yogurt manufacture was prepared, and calcium was added or removed from the system. Calcium was added as Ca²⁺ in the form of CaCl₂ (up to 13.6 mM) or nonionic calcium as Gadocal-K (calcium potassium citrate; up to 49.8 mM). Calcium was removed by chelating with sodium citrate (up to 16 mM) or by cation exchange with Amberlite IR-120 plus (sodium form) resin (up to 10 g/L). Calcium chloride and sodium citrate were added either before or after heat treatment of milk, and nonionic calcium was added before heat treatment. Calcium removal by ion exchange was performed before heat treatment. Neither Ca²⁺ addition nor removal by chelation with citrate resulted in stirred yogurt with viscosity, firmness, and smoothness superior to those of the control yogurt, whereas addition of 49.8 mM nonionic calcium and removal of calcium (5.6 mM or ∼10% of total calcium) by cation exchange improved the firmness and viscosity without affecting yogurt smoothness. The study identified Gadocal-K as a possible source of calcium fortification of stirred yogurt without loss of texture.     

搅拌型酸奶黏度特性的研究与改进

为了解决搅拌型酸奶黏度问题,本文研究了凝固型和搅拌型酸奶黏度特性的差别.结果表明,在提高酸奶的黏度和稳定性方面,添加复合稳定剂比单一稳定剂效果好;其中0.50%果胶与0.25%明胶的复合稳定剂效果最好.     

香蕉酸奶的工艺优化及质构特性研究

以香蕉酸奶为研究对象,在单因素实验的基础上,选取乳酸菌添加量、发酵温度、发酵时间为自变量,感官评定得分为响应值,利用Box-Behnken中心组合设计原理和响应面分析法,对香蕉酸奶的发酵工艺进行优化。确定其最优工艺参数为乳酸菌添加量0.1%、发酵温度40℃、发酵时间7.6h,感官评分可达15.19。建立质构特性与感官得分之间的线性回归模型为:y（感官评定得分）=18.114-0.157x1（硬度）-3.211x2（粘性）-0.324x4（弹性）。      

搅拌型苹果酸奶稳定性的研究

通过对搅拌型苹果酸奶稳定性的研究,获得了重要的工艺参数和技术要点。实验结果表明,在能够打碎酸凝乳条件下,以慢速搅拌效果较好;添加0.6%～0.8%浓缩苹果汁,0.15%果胶和0.15%明胶,产品均匀细腻,质量稳定。     

搅拌型树莓酸奶的工艺研究

以奶粉、树莓、白糖为主要原料,采用单因素试验和感官评价打分,制出搅拌型树莓酸奶并确定其最佳生产工艺:奶粉添加量为13%,树莓果汁的最适添加量为3.5%,白砂糖的最适添加量为8%,接种量为4%,发酵温度为43℃,发酵时间为3~4h。所得产品口感柔和爽快,风味独特,营养丰富。     

老鹰茶对搅拌型酸奶品质的影响

牛乳经杀菌、冷却和接种等步骤处理后,在42℃发酵7 h使其完全凝乳,按0.2~1 m L/100 m L的比例添加老鹰茶水提浓缩液,并破乳混匀得搅拌型老鹰茶酸奶。搅拌型老鹰茶酸奶在8℃下冷藏5周,考察老鹰茶水提浓缩液对搅拌型酸奶的感官理化品质和乳酸菌数的影响。结果表明:搅拌型老鹰茶酸奶具有良好的感官品质,具有老鹰茶特有的色泽和风味,其主要理化指标和乳酸菌总数均符合GB 19302的相关规定。与对照酸奶相比,搅拌型老鹰茶酸奶的茶多酚含量、持水力和粘度均有不同程度增加。老鹰茶水提浓缩液可促进嗜热链球菌的生长,而对鼠李糖乳杆菌、嗜酸乳杆菌、干酪乳杆菌和德氏乳杆菌保加利亚亚种的生长促进作用不明显。      

Effect of trisodium citrate on rheological and physical properties and microstructure of yogurt

The effect of trisodium citrate (TSC) on the rheological and physical properties and microstructure of yogurt was investigated. Reconstituted skim milk was heated at 85° C for 30 min, and various concentrations (5 to 40 mM) of TSC were added to the milk, which was then readjusted to pH 6.50. Milk was inoculated with 2% yogurt culture and incubated at 42° C until pH was 4.6. Acid-base titration was used to determine changes in the state of colloidal calcium phosphate (CCP) in milk. Total and soluble Ca contents of the milk were determined. The storage modulus (G′) and loss tangent (LT) values of yogurts were measured as a function of pH using dynamic oscillatory rheology. Large deformation rheological properties were also measured. Microstructure of yogurt was observed using confocal scanning laser microscopy, and whey separation was also determined. Addition of TSC reduced casein-bound Ca and increased the solubilization of CCP. The G′ value of gels significantly increased with addition of low levels of TSC, and highest G′ values were observed in samples with 10 to 20 mM TSC; higher ( > 20 mM) TSC concentrations resulted in a large decrease in G′ values. The LT of yogurts increased after gelation to attain a maximum at pH ∼5.1, but no maximum was observed in yogurts made with ≥ 25 mM of TSC because CCP was completely dissolved prior to gelation. Partial removal of CCP resulted in an increase in the LT value at pH 5.1. At low TSC levels, the removal of CCP crosslinks may have facilitated greater rearrangement and molecular mobility of the micelle structure, which may have helped to increase G′ and LT values of gels by increasing the formation of crosslinks between strands. At high TSC concentrations the micelles were completely disrupted and CCP crosslinks were dissolved, both of which resulted in very weak yogurt gels with large pores obvious in confocal micrographs. Gelation pH and yield stress significantly decreased with the use of high TSC levels. Lowest whey separation levels were observed in yogurt made with 20 mM TSC, and whey separation greatly increased at > 25 mM TSC. In conclusion, low concentrations of TSC improved several important yogurt characteristics, whereas the use of levels that disrupted casein micelles resulted in poor gel properties. We also conclude that the LT maximum observed in yogurts made from heated milk is due to the presence of CCP because the modification of the CCP content altered this peak and the removal of CCP eliminates this feature in the LT profiles.     

Potential effects of ultrafiltration process and date powder on textural,sensory, bacterial viability,antioxidant properties and phenolic profile of dromedary Greek yogurt

The aim of this study was to improve textural and antioxidant capacity of dromedary yogurt using ultrafiltration process and date powder. Ultrafiltration increased total solids content of dromedary milk within the range considered optimal to develop yogurt. Texture profile of Greek yogurt fortified with date powder (GYD) improved considerably compared to control. Sample of GYD are more appealing to consumer than control. LC-ESI-MS analysis of GYD extracts allowed the identification of fifteen phenolic compounds, among which quinic acid and cirsiliol were found to be the major phenolic acid and flavonol, respectively. GYD exhibited the highest DPPH•-radical scavenging activity, Fe²⁺ chelating capacity and Fe³⁺ reducing power. The follow-up of physical and microbiological stability of GYD and control during cold storage showed that date powder significantly increased bacterial counts and decreased syneresis. Therefore, ultrafiltration and date powder could be valued as effective tool to solve the poor consistency of dromedary milk products.     

桑椹果渣中桑椹红色素的提取工艺研究

桑椹红色素是一种安全、无毒的食用天然色素。以桑椹果渣为原料,采用溶剂浸提法对桑椹红色素的提取工艺进行了系统研究,结果表明,最佳提取条件为溶剂配比为含0.01%HCl的80%乙醇溶液、料液比1:20、温度20℃、浸提时间1h、一级提取,色素的提取率为93.07%。     

酸浆果保健酸乳的质地及理化性质研究

以蛋白质含量、脂肪含量、pH值、持水力、流变学特性和质构特性为主要测定指标,通过单因素试验,研究了酸浆果浆添加量 对酸乳理化及感官性质的影响。结果表明,酸浆果浆添加量的变化对酸乳的理化及感官性质有明显影响;酸浆果浆添加量为10%的 酸乳样品在5组样品中感官评分最高（94.7分）,各项理化指标均符合发酵乳国家标准;酸乳样品的黏聚性和胶着性分别与硬度具有 显著相关性（P＜0.05）;所酿造的酸浆果保健酸奶呈现均匀的橙黄色,组织细腻,具有酸浆果特有的香味,酸甜爽口。     

Comparison of the functionality of exopolysaccharides produced in situ or added as bioingredients on yogurt properties

The effect on yogurt properties of in situ production of exopolysaccharides (EPS) and addition of 2 EPS powders (crude and purified EPS from Lactobacillus rhamnosus RW-9595M fermentation in whey-based medium) at different concentrations was studied. No effect of purified powder addition for EPS concentrations up to 500 mg/L was observed on acidification rate to the difference of milks supplemented with crude EPS, which exhibited longer acidification times. The addition of EPS from 125 to 500 mg/L or the use of EPS-producing cultures resulted in yogurts with lower yield stress and viscoelastic moduli compared with control yogurts without EPS, with no apparent effect of EPS concentration. However, the consistency index was higher for yogurts produced with the commercial EPS-producing culture, and to a lesser extent with the mixed culture containing Lb. rhamnosus RW-9595M, compared with yogurts supplemented with EPS powders, which were not different from that for control yogurts. Our study showed that the mode of EPS incorporation in yogurts has a major effect on the rheological properties of the final product.     

四种方法提取苹果肉渣果胶的流变学特性研究

采用传统酸法(TA)、纤维素酶法(CL)、超声辅助法(UA)和微波辅助法(MA)提取苹果肉渣果胶并对其进行鉴定,考察剪切速率、浓度、温度和放置时间对四种果胶流变学特性的影响,并测定黏均分子量来验证其流变学特点。结果表明:果胶溶液的表观黏度随剪切速率的增加而降低,为典型的非牛顿流体中的假塑性流体行为。果胶溶液浓度越大,剪切稀化现象越明显。温度升高会使果胶溶液表观黏度降低。放置时间越久,果胶溶液的表观黏度越小。四种果胶溶液的表观黏度和黏均分子量大小顺序均为:TA>CL>UA>MA,黏均分子量的测定结果从理论上很好地验证了其流变学特点。      

Effect of sequential treatments of fermentation and ultrasonication followed by extrusion on bioactive content of apple pomace and textural,functional properties of its extrudates

Apple pomace (AP) is a potential source of phenolic compounds, and most of the phenolics are presented in the bound form. Liberation of these bound phenolics is required to improve their health functionality. In this context, AP was naturally fermented followed by the ultrasonication and microwave drying. Fermentation time (FT), pomace to water ratio (PWR), ultrasonication intensity (UI) and microwave power (MWP) had significant (P < 0.05) effect on total phenolic content (TPC) and antioxidant activity (AA) of AP. At the optimum pretreatment conditions of 24 h FT, 5% (w/v) PWR, 37 W cm^?2 UI and 90 W MWP, TPC and AA of AP were 40.3% and 92.9%, respectively, higher than that of the control AP. Extrudates from pretreated AP also had improved textural (hardness, brittleness, crispness) and functional (water absorption index, water solubility index) properties. Pretreatment reduced crystalline fraction amount and enhanced solubility of AP.     

Structure and physical properties of yogurt gels: effect of inoculation rate and incubation temperature

The effects of inoculation rates and incubation temperatures on the physical properties and microstructure of yogurt gels were investigated. A 2-factor experimental design with 3 replicates was used for data analysis. Yogurt gels were made with 0.5, 1, 2, 3, or 4% (wt/wt) inoculation rates and incubated at 40 or approximately 46 degrees C. Dynamic low amplitude oscillatory rheology was performed to monitor the formation of yogurt gels. Gel permeability and the amount of surface whey were determined. Gel structure was examined by confocal scanning laser microscopy. Higher storage modulus values were observed in yogurt gels made at higher inoculation rates and lower incubation temperatures. Gels made at higher inoculation rates and incubation temperatures exhibited higher yield stress and maximum loss tangent values, respectively. Permeability, pore size, and whey separation of yogurt gels increased with decreased inoculation rate and increased incubation temperature. An increase in the inoculation rate resulted in a decrease in the pH where the maximum in the loss tangent occurs, presumably reflecting less efficient solubilization of colloidal calcium phosphate (which is a slow process) and the need to attain a lower pH to complete the solubilization. Significant positive correlations were observed between whey separation and the value of maximum in loss tangent (r = 0.94) and permeability (r = 0.89). Whey separation was negatively correlated with storage modulus (r = -0.48). It was concluded that rearrangements of casein particles in the gel network and the rate at which the solubilization of colloidal calcium phosphate occurred were important driving forces for whey separation and weak gel.