蓝莓浓缩汁流变特性及化学组成的变化

流体的流变学可为工艺设计提供有关数据,并有助于找出产品组成及加工工艺对流变性质的影响。本研究采用AR1000型流变仪研究了浓缩蓝莓汁(60°Brix)在(20～60℃)范围内的流变特性。通过回归分析发现,在研究的温度和浓度范围内,浓缩蓝莓汁表现为牛顿型流体,温度对粘度的影响可用阿雷尼乌斯(Arrhenius)方程来表示,浓度对粘度的影响可用指数方程来表示。推导出了温度和浓度对浓缩蓝莓汁粘度综合影响的方程式并比较了浓缩前后蓝莓汁化学组成的变化。     

Phase and rheological behavior of high-concentration colloidal hard-sphere and protein dispersions

ABSTRACT:  Colloidal hard-sphere (HS) particles of narrow-size distribution exhibit crystalline and glassy states beginning at the particle volume fractions φ= 0.494 and φ_G= 0.58, respectively. Dynamic rheological data on the dispersions were strongly modified to solid-like behavior as φ approached φ_G. In addition, cooperative motion in structural relaxation has been observed microscopically in the colloidal dispersions near the glassy state. Very high viscosities and glassy states were also found in high-concentration dispersions of sodium caseinate and the globular proteins: bovine serum albumin and β-lactoglobulin. Viscosity models developed for HS dispersions predicted accurately the trends but not the absolute values of protein dispersions. Dispersions of food colloidal particles may be employed in studies, in which volume fraction is the thermodynamic variable, for understanding the relaxation and transport processes related to 1st-order and colloidal glass transitions.     

浓缩苹果汁中耐高渗透压酵母菌的分离与培养条件优化研究

对浓缩苹果汁中的耐高渗透压酵母菌进行分离与鉴定,并采用正交试验对培养条件中的蔗糖浓度、pH值、果汁稀释度、培养温度进行了优化研究。以菌落生长状况作为综合评价依据,试验结果表明,分离出的耐高渗透压酵母菌不是单一菌种,表现为多形态;高浓度蔗糖对耐高渗透压酵母菌的生长有显著地抑制作用;分离培养耐高渗透压酵母菌的优化组合为A1B4C3D3,即pH值为3.6,稀释比例1:40,培养基中蔗糖浓度60%,培养温度30℃。     

苹果汁、酵母对苹果酒酿造的影响

以红富士苹果和浓缩果汁为原料酿造苹果酒。以亚硫酸的形式将SO2(120mg/L)加入苹果汁中，24h后90％以上的游离SO2变为结合态，此后波动不大。研究显示：1．5‰的皂土澄清效果最好；鲜汁的产酒率明显高于浓缩汁，酒液中可溶性固形物和还原糖少。与其它菌种相比，菌种1的产酒率最高，残糖最少，挥发酸最少，而且滴定酸，pH的变化幅度较少。与浓度果汁相比，鲜果汁酿造的酒中含有的香气成份如活性戊醇 异戊醇、正戊醇、正己醇、苯乙酸乙酯较多。     

不同黏度魔芋葡甘聚糖对食欲和能量摄入量的影响

目的探讨食品的黏度特性对受试者餐后食欲和能量摄入量的影响。方法通过网络发布3因素进食问卷(three-factor eating questionnaire, TFEQ)招募受试者;以视觉模拟评分法(visual analogue scales, VAS)记录受试者餐后的饥饿感、饱腹感、进食欲望和期望进食量的变化;计算受试者的平均食欲率(meanappetite ratings, MAR)及其食欲的曲线下面积(area under the curve, AUC),并以此作为测试餐饱腹性能的评价指标;为受试者提供随意午餐并记录其进食至完全满足时的能量摄入量。结果同控制组测试餐相比,低、中、高黏度测试餐的饱腹感指数(satiety index, SI)依次达到了127.63%、141.81%和178.43%。并且,与控制组受试者相比,低、中、高黏度组受试者的饱腹感依次提高了31.50%、46.66%和78.63%,饥饿感则分别下降了28.54%、42.92%和60.93%。经不同黏度的测试早餐干预后,在随后的测试午餐实验中,低、中、高黏度组受试者的能量摄入量相比于控制组依次下降了6.69%、10.40%和12.50%。结论食物的黏度对受试者的食欲有显著的影响,一定范围内,食物的黏度越大,其饱腹感指数越大,受试者的饱腹感也随之增加,而饥饿感随之减小。因此,利用魔芋葡甘聚糖(konjacglucomannan,KGM)的高黏特性可以显著提升食物的饱腹性能,从而有效抑制受试者餐后的进食欲望并降低其能量摄入量。     

酵母菌与乳酸菌发酵对小米淀粉粘度的影响

自然发酵受环境和微生物的影响大,难实现发酵产品的大规模生产。故研究自然发酵优势菌对小米淀粉的影响很有必要。选取内蒙古赤峰生产的黄金苗小米为原料,利用自然发酵纯化的酵母菌与乳酸菌为菌种进行纯种发酵96 h,并且与自然发酵后的小米淀粉比较,分析淀粉的粘度、衰减值和回生值的变化。采用0.2 g/100 m L的Na OH溶液提取3 h的方法来提取发酵后小米中的淀粉,并对其发酵液中固形物的含量、p H、淀粉的粘度特性、偏光十字进行测定。结果表明,三种发酵方法所得的发酵液中总固形物的含量都增加;较自然发酵相比,发酵前24 h乳酸菌和酵母菌发酵液中的p H下降迅速,之后变化缓慢;淀粉粘度特性表明,乳酸菌和酵母菌发酵终止时,其粘度的起始温度、衰减值、回生值较自然发酵相比都下降,峰值粘度较自然发酵相比都上升,乳酸菌发酵和酵母菌发酵的最终粘度与自然发酵相比有所增加,偏光十字显示无论是自然发酵酵母菌发酵还是乳酸菌发酵,发酵后的淀粉颗粒仍具有偏光十字,说明发酵未改变淀粉的结晶结构。      

AOS、LAS复配洗涤剂粘度对温度敏感性的影响

采用阿累尼乌斯方程描述了AOS、LAS复配液体洗涤剂粘度与温度的变化关系．实验结果表明，随体系中AOS含量的增加，体系表观活化能的绝对值减小，体系粘度对温度的敏感性降低。     

Rheological behaviour of acorn starch dispersions: effects of concentration and temperature

Rheological properties of acorn starch dispersions at different concentrations (4%, 5%, 6% and 7%) were evaluated under steady and dynamic shear conditions. The flow behaviours of the acorn starch dispersions at different temperatures (25, 40, 55 and 70 °C) were determined from the rheological parameters provided by the power law model. The acorn starch dispersions at 25 °C exhibited high shear-thinning fluid characteristics ( n  = 0.23–0.36). Consistency index (K) and apparent viscosity (η_a,100) increased with an increase in starch concentration, and were also reduced with increasing temperature. Within the temperature range of 25–70 °C, the η_a,100 obeyed the Arrhenius temperature relationship with a high determination coefficient ( R ² = 0.97–0.99), with activation energies (E_a) ranging between 16.5 and 19.0 kJ mol⁻¹. Both the power law and exponential type models were employed in order to establish the relationship between concentration and apparent viscosity (η_a,100) in the temperature range of 25–70 °C. Magnitudes of storage ( G' ) and loss ( G ") moduli increased with an increase in the starch concentration and frequency (ω). The magnitudes of G ' were higher than those of G " over most of the frequency range (0.63–62.8 rad s⁻¹). The dynamic (η*) and steady shear (η_a) viscosities of acorn starch dispersion at 7% concentration follow the Cox–Merz superposition rule.     

Effect of processing technique on energy density and viscosity of cooking banana: implication for weaning foods in Uganda

The type and quality of weaning food plays a vital role in the growth and development of children. The high rates of malnutrition reported in banana consuming areas of Uganda reveal the bulkiness and high viscosity of the predominant banana-based weaning foods. The objective was to determine the impact of processing technique on energy density and viscosity of cooking banana. Part of the unprocessed dried slices was milled into fine flour and the rest extruded. Pre-gelatinised banana flour was produced using a modified earlier method. Nutrient and energy composition of the flours were determined using standard methods. Data were subjected to one-way anova /least significant difference test and t -test using GenStat 5 Release 3.2. Pre-gelatinisation and extrusion cooking significantly raised energy content of banana significant impact on its viscosity but with extrusion cooking achieving better results. Extrusion cooking and pre-gelatinisation increase the energy content of cooking bananas and significantly reduces its bulkiness. Soybean and simsim addition will improve protein quality and quantity of banana-based weaning products.     

颜料水性分散体系用高分子分散剂的合成与表征

采用苯乙烯和马来酸酐为单体合成了用作颜料水性体系分散剂的高分子共聚物，FT-IR的分析结果表明，用作分散剂的水溶性共聚物SMH是SMA部分水解的产物；共聚物SMA的^13CNMR核磁共振法和滴定法结果表明其序列结构为三元结构，单元“SSM”占绝对优势，其它的结构单元摩尔分数极小；凝胶色谱GPC的分析表明，共聚物SMA的数均分子质量为4934，重均分子质量为9759，多分散指数是1．978．     

Use of reconstituted concentrated nonfat milk for the production of UHT milk: physical and chemical effects and stability

The objective of this work was to evaluate the use of reconstituted concentrated nonfat milk for the production of UHT milk and to evaluate its physical and chemical effects and stability. The study considered three treatments related to the raw material and processing parameters. Increasing the intensity of thermal treatments resulted in increased hydroxymethylfurfural (HMF) content as well as the denaturation of whey protein. During storage, the milk that was produced from reconstituted concentrate displayed a lesser degree of proteolysis and higher pH value, sedimentation index and HMF, compared to natural milk. Under higher storage temperatures, the degree of proteolysis, HMF and pH decreased and the sedimentation index increased.     

线性微分方程化为常系数方程的充要条件

给出了高阶变系数线性微分方程通过变换化为常系数方程的一个充要条件     

Extension of the Vane Pump‐Grinder Technology to Manufacture Finely Dispersed Meat Batters

A vane pump‐grinder system was extended to enable the manufacture of finely dispersed emulsion‐type sausages by constructing and attaching a high‐shear homogenizer at the outlet. We hypothesized that the dispersing capabilities of the extended system may be improved to the point of facilitating meat‐fat emulsification due to an overall increased volumetric energy input E_V. Coarsely ground raw material mixtures were processed to yield meat batters at varying volume flow rates (10 to 60 L/min) and rotational rotor speeds of the homogenizer n_rotor (1000 to 3400 rpm). The normalized torques acting on pump, grinder, and homogenizer motors were recorded and unit power consumptions were calculated. The structure of the manufactured meat batters and sausages were analyzed via image analysis. Key physicochemical properties of unheated and heated batters, that is, texture, water‐binding, color, and solubilized protein were determined. The mean diameter d₁₀ of the visible lean meat particles varied between 352 and 406 μm whereas the mean volume‐surface diameter d₃₂ varied between 603 and 796 μm. The lightness L* ranged from 66.2 to 70.7 and correlated with the volumetric energy input and product structure. By contrast, varying process parameters did not impact color values a* (approximately 11) and b* (approximately 8). Interestingly, water‐binding and protein solubilization were not affected. An exponential process‐structure relationship was identified allowing manufacturers to predict product properties as a function of applied process parameters. Raw material mixtures can be continuously comminuted, emulsified, and subsequently filled into casings using an extended vane pump‐grinder.     

Rates of starch hydrolysis and changes in viscosity in a range of common foods subjected to simulated digestion in vitro

A range of common starch-rich foods and pure starches was analysed for available carbohydrates and dietary fibre content, and subjected to a simulated digestion procedure in vitro. The initial rates of free sugar release differed markedly between foods; the time required for the release of 50% of the starch content of some legumes was up to 100 fold longer than that for foods such as potatoes and rice. A significant correlation (r=0.806; P<0.01) between the time required for hydrolysis and the total dietary fibre content of the foods was observed. The viscosity of the food samples declined during the course of digestion, but always remained markedly higher than that of pure starch. The rate of hydrolysis of starch appears to be the most important factor governing the human glycaemic response to foods described by other authors, but the final viscosity of partially digested foods may be of some significance.     

青岛啤酒酵母与高浓酵母筛选高浓酿造酵母融合亲株100L发酵分析

以青岛啤酒酵母T1、T2、T3和高浓酵母G4、G6为供试菌株,筛选生长良好的酵母,为筛选具有青岛啤酒风味的高浓酵母原生质体融合亲株做指导。比较了5株酵母菌100L发酵过程中酵母菌数量、双乙酰变化及待滤酒发酵度、酸度、α-氨基氮同化率等指标。结果表明:G4和G6酵母数量变化、双乙酰变化、发酵度和α-氨基氮同化率指标优于T1、T2和T3,青岛啤酒酵母中T1和T3除酵母凝聚性外其他指标都优于T2。因此,确定T1、T3和G4、G6为融合亲株。      

Influence of particle characteristics and E/Z‐isomer ratio on the colour of concentrated β‐carotene dispersions

The influence of particle concentrations (0.02–0.40%), mean particle sizes (0.45–1.5 μm) and all‐E‐isomer ratios (95–30%) on the CIELAB colour coordinates (L*, a*, b*) of concentrated β‐carotene dispersions was investigated. Particle concentration between 0.06% and 0.40% had a slight impact on the colour parameters. However, with decreasing the mean particle size from 1.50 to 0.45 μm, there were increases in ΔL* = 8.0, in Δa* = 2.26 and in Δb* = 13.1. And with decreasing the all‐E‐isomers ratio from 95% to 30%, there were increases in ΔL* = 8.66, in Δb* = 17.51 but decrease in Δa* = 7.42. The experimental results were explained in terms of the scattering and absorption of light by dispersions. These findings have important implications for food industry as they offer a means to control and optimise the colour of food dispersions.     

Stability of anthocyanins in frozen and freeze-dried raspberries during long-term storage: in relation to glass transition

Abstract: Anthocyanins, natural plant pigments in the flavonoid group, are responsible for the red color and some of the nutraceutical benefits of raspberries. This study explores anthocyanin degradation in frozen and freeze‐dried raspberries during storage in relation to glass transition temperatures. Frozen raspberries were stored at ?80, ?35, and ?20 °C, while freeze‐dried raspberries were stored at selected water activity (a_w) values ranging from 0.05 to 0.75 at room temperature (23 °C) for more than a year. The characteristic glass transition temperatures (T′_g) of raspberries with high water content and glass transition temperature (T_g) of raspberries with small water content were determined using a differential scanning calorimeter. The pH differential method was used to determine the quantity of anthocyanins in frozen and freeze‐dried raspberries at selected time intervals. The total anthocyanins in raspberries fluctuated during 378 d of storage at ?20 and ?35, and ?80 °C. Anthocyanin degradation in freeze‐dried raspberries ranged from 27% to 32% and 78% to 89% at a_w values of 0.05 to 0.07 and 0.11 to 0.43, respectively, after 1 y. Anthocyanins were not detectable in freeze‐dried raspberries stored at a_w values of 0.53 to 0.75 after 270 d. First order and Weibull equations were used to fit the anthocyanin degradation in freeze‐dried raspberries. The 1^st‐order rate constant (k) of anthocyanin degradation ranged from 0.003 to 0.023 days^?1 at the selected water activities. Significant anthocyanin degradation occurred in both the glassy and rubbery states of freeze‐dried raspberries during long‐term storage. However, the rate of anthocyanin degradation in freeze‐dried raspberries stored in the glassy state was significantly smaller than the rate of anthocyanin degradation in the rubbery state.     

不同浓缩乳制品产品标准的比较研究——基于对术语、分类、定义及相关条款的分析和讨论

炼乳等浓缩乳制品是我国市场和国际贸易常见的乳制品种类,随着行业发展和新产品的出现,产品标准的管理内容也在不断修订和更新。通过比较研究国内外标准的内容及管理思路的异同,有助于正确借鉴国外标准管理经验,不断完善我国标准。在回顾我国浓缩乳制品国家标准的发展和沿革的基础上,通过收集和整理国际食品法典委员会产品标准,以及欧盟、美国、加拿大、日本、韩国、澳大利亚和新西兰等国家或地区浓缩乳制品强制性标准及法规等相关管理规定,分析比较了不同标准中各类浓缩乳制品的术语、定义、分类、相关指标要求、标签标识等产品标准核心内容的异同,重点对淡炼乳的定义、浓缩乳的产品属性和成分要求,以及各类浓缩乳制品术语在不同标准体系中的对应关系等进行了研究和讨论,提出了浓缩乳制品产品标准需要关注的重点内容及管理建议,以期为我国标准管理工作提供参考。     

Using promoter replacement and selection for loss of heterozygosity to generate an industrially applicable sake yeast strain that homozygously overproduces isoamyl acetate

By application of the high-efficiency loss of heterozygosity (HELOH) method for disrupting genes in diploid sake yeast (Kotaka et al., Appl. Microbiol. Biotechnol., 82, 387–395 (2009)), we constructed, from a heterozygous integrant, a homozygous diploid that overexpresses the alcohol acetyltransferase gene ATF2 from the SED1 promoter, without the need for sporulation and mating. Under the conditions of sake brewing, the homozygous integrant produced 1.4 times more isoamyl acetate than the parental, heterozygous strain. Furthermore, the homozygous integrant was more genetically stable than the heterozygous recombinant. Thus, the HELOH method can produce homozygous, recombinant sake yeast that is ready to be grown on an industrial scale using the well-established procedures of sake brewing. The HELOH method, therefore, facilitates genetic modification of this rarely sporulating diploid yeast strain while maintaining those characteristics required for industrial applications.