国外资讯

正无需拆封即可检测牛奶是否变质的新型传感器来自华盛顿州立大学生物系统工程系(BSE)、食品科学学院等部门的研究人员开发出一种新型传感器,可以"闻"出牛奶是新鲜还是已变质。据BSE的Shyam Sablani教授介绍,该传感器是由纳米粒子化学涂层组成,这些纳米粒子可对牛奶以及预示着牛奶变质的细菌滋生所产生的气体作出反应,而这个过程中传感器不直接接触牛奶。     

牛奶果汁饮料变质原因的研究

应用微生物学方法，对牛奶果汁饮料变质的原因进行了研究，结果表明牛奶果汁饮料的变质是由于冷却水中的微生物污染所致。     

流通环境对牛奶包装阻氧性能的影响

<正>测试高温以及揉搓条件下牛奶包装材料的透氧率是非常必要的。牛奶对包装材料阻氧性能的要求很高。当包装内渗入的氧气达到一定含量时,牛奶中的脂肪会氧化变质,同时牛奶也因滋生大量细菌发生变质。所以,包装材料阻氧性能的优劣是影响牛奶保质期的直接原因。针对不同种类牛奶的特点,乳品企业会选择不同的包装材料及存储条件,以确保产品保质期。常见的液态     

牛奶中加入红糖煮沸后引起酪蛋白凝结的研究

在牛奶卫生监督工作中,于一个时期内,曾连续有群众反映,当牛奶中加入红糖煮沸后,奶汁中即有“豆腐花”状凝块出现,认为牛奶变质。为了弄清牛奶中酪蛋白之凝结系变质所致抑加入红糖所引起,我们曾进行有关实验,并找出了原因,兹报告如下。实验的经过和结果一、观察牛奶在不同酸度下加入红糖煮沸后有无不同变化:将同一份牛奶经不同时     

美研究显示:LED灯照射会加速牛乳变质

正康乃尔大学的研究人员发现即使是受到LED光源照射短短数小时,也会加速牛奶变质,甚至比牛奶中随时间增加的微生物造成牛奶变质还要快。研究人员假设,没有受到LED光照射的情况下,牛奶的品质能够维持良好达两周之久。而面对存放较久的牛奶跟仅仅受到LED光照4 h、装在一般透光容器中的牛奶,消费者一边倒的选择前者。随着商人开始在乳制品集送和销售地点使用LED灯等节能光源,他们可能也不知不觉地破坏了乳制品的品质。     

低能超声波检测技术在乳制品工业中的应用研究进展

低能超声波检测技术能无损测定多种食品的品质,如肉、鱼和乳制品等。在阐述低能超声波(LIU)检测技术原理的基础上,概括介绍了该检测技术在乳制品(牛奶和奶酪)成分的测定、质构特性(黏度和弹性等)的测定以及异物和添加剂检出等方面的应用研究进展。     

信息

新型牛奶杯可随时监测牛奶是否变质据国外媒体报道,Quirky是位于美国纽约的创意产品社会化电商,它的产品研发团队通过与通用电器(GE)合作,研制出了一项新产品,能够对牛奶或杯子里剩余牛奶的质量     

安全包装有效延长货架期保障鲜奶品质

众所周知，牛奶是非常容易被污染、易变质的敏感高营养品，如何尽量的减少牛奶中的细菌总量又同时最大限度的保护牛奶中原来的营养，是全世界乳品企业一直努力的方向。     

基于磁弹性传感器的金黄色葡萄球菌检测机理研究

针对乳制品中可能含有金黄色葡萄球菌的问题,研制了用于检测金黄色葡萄球菌的无线磁弹性传感器,研究该磁弹性传感器检测机理,对比分析磁弹性无线传感器在有菌和无菌的乳制品中共振频移以及荧光。结果表明,磁弹性传感器的共振频率能够较好地反映传感器自身的重量和传感器所处液体的黏度,由于金黄色葡萄球菌的增殖会引起牛奶黏度的变化,且金黄色葡萄球菌会与修饰在膜片的适配体结合引起质量变化,从而影响传感器的共振频率。通过试验验证液体黏度对磁弹性传感器振动频率的抑制也较为明显,当黏度变化只有0.15mPa·s时,其共振频移能够达到0.5kHz。     

牛奶中过氧化氢快速检测试纸条的研制

当前,食品安全问题日益突出,其中乳制品安全问题也备受关注,为了防止牛奶变质,不法经营者向牛奶中掺入过氧化氢,对消费者健康造成巨大威胁。传统的过氧化氢检测方法复杂且耗时较长,为满足现场快速、准确检测过氧化氢残留的需求,本研究利用酶促反应原理,将含有1g/L的四甲基联苯胺(TMB)和10μg/mL的辣根过氧化物酶(HRP)混合溶液作为显色剂,并加入适当的保护剂,以定量滤纸为载体,经真空干燥并加工制成过氧化氢快速检测试纸条。该试纸条能够在10秒钟内对牛奶中的过氧化氢残留进行半定量检测,最低检出限达到0.5mg/L,并且操作简单,价格低廉,十分适用于奶制品厂和基层奶站的现场检测。     

Long term storage of some dry foods: a discussion of some of the principles involved

Foods which have been dried to the point where microbiological growth is inhibited can still deteriorate through chemical, biochemical and physical changes. Keeping foods cool and dry is normally the best way of minimizing these changes but this is not universally the case. Some exceptions are discussed in relation to the scientific principles underlying storage practice with flour, fats, yeast, sugar and dried milk. The mechanisms involved in loss of baking quality of flour, β-carotene deterioration in fats, loss of gassing power in yeast, syrup formation in sugar and loss of solubility in dried milk are discussed.     

Evaluation and validation of an inline Coriolis flowmeter to measure dynamic viscosity during laboratory and pilot-scale food processing

Inline process analytical technology tools are increasingly employed in industry as they facilitate real time process parameter monitoring and optimization of product quality. Use of an inline viscometer in milk powder manufacture allows greater process control by monitoring the dynamic viscosity of the process concentrate pumped to the spray drier. In this study, an inline Promass I300 was used to measure the dynamic viscosity of both a Newtonian fluid (10–60% w/w sucrose solutions) and a non-Newtonian fluid (10–40% w/w skim milk concentrate) at laboratory scale at 25 °C. Validation of the instrument for measurement of a non-Newtonian fluid was completed at pilot-scale under similar operating conditions. Coefficient of determination (R² = 0.99) was obtained between inline and offline viscosity measurements for both Newtonian and non-Newtonian fluids investigated. This study demonstrated the potential of an inline Coriolis flowmeter for rapid and accurate measurement of dynamic viscosity during processing of dairy streams.Industrial relevanceControl of milk concentrate viscosity during the manufacture of milk powder is critical to reduce energy consumption, reduce fouling and meet powder functional properties e.g. dispersability, flowability, particle size and powder hydration. The use of inline instruments for continuous monitoring of viscosity offers economic benefits to the producer as it can contribute to reduction in commonly encountered process issues such as fouling, blocking of nozzles and evaporator, which can result in process downtime and in extreme cases, product rework. Inline instruments can thus be employed to improve process control and reduce production waste during the manufacture of dairy powders.     

米糠膨化

由于米糠中含有极其活泼的解脂酶,致使米糠在贮运、制油过程中易发生劣变,大大地限制了米糠制油的发展。米糠膨化,不仅解决了防止米糠酸败、稳定米糠品质问题,而且起到了传统油脂加工工艺中轧胚、蒸沙所要达到的破坏细胞,蛋白质变性、传质、传热,降低油脂粘度,使大量油脂由结合态变为游离态,以利于制油的目的。分析了影响米糠酸败变质的主要因素,阐述了米糠膨化目的和在生产过程中影响米糠膨化的诸多条件以及膨化前后米糠的物性变化;简要介绍了国内外几种米糠膨化设备的主要技术经济指标。     

嗜冷茵对UHT奶品质影响的研究

嗜冷菌产生耐热蛋白酶和脂肪酶是UHT奶在长期存放过程中产生劣变的主要原因之一。原料乳中蛋白酶、脂肪酶的活性与产品长期保存时的品质呈负相关。通过控制原料奶乳中嗜冷菌数,测定蛋白酶和脂肪酶活力,对原料奶进行分级和评价是确保UHT奶品质的一种有效手段,本实验为乳品企业嗜冷菌的检测提供了理论依据。     

Effect of different pre-treatments of fresh coconut kernels on some of the quality attributes of the coconut milk extracted

Fresh, dehusked and shelled coconut kernels were subjected to blanching and freezing treatments and were tested for chemical and enzymatic deterioration and yield of milk by monitoring the percentage extraction of coconut milk, free fatty acid (FFA) content, peroxide value (PV), lipase (LIP) and peroxidase (POD) activities, once each fortnight for a total period of 8 weeks. The percentage extraction of milk varied between 31.0% and 33.5% in the blanched samples and did not show a significant change at p > 0.05, as compared to the values at week 0. Similar observations were seen in FFA content and the PV. The LIP activity in these samples decreased to almost 0.176% liberated FFA and POD activity to 0.387 Absorbance Units/g fresh-weight. In conclusion, the results indicated the efficiency of the pre-treatment in suppressing the chemical and enzymatic deterioration of coconut kernels, which normally results in the loss of quality of the coconut milk when extracted.     

Guideline for proper usage of time temperature integrator (TTI) avoiding underestimation of food deterioration in terms of temperature dependency: A case with a microbial TTI and milk

Time-temperature integrators (TTIs) can be used to predict food deterioration. However, underestimation of the magnitude of deterioration is not desirable. This study aims to establish guidelines in terms of temperature dependency (Arrhenius activation energy, Ea) to avoid such underestimation by proper use of TTIs. A case study was executed with a microbial TTI and milk. The Ea of the TTI color change was 106 kJ/mol and those of milk deterioration factors aerobic mesophilic bacteria count, lactic acid bacteria count, ln lactic acid %, and pH were 101, 107, 122, and 145 kJ/mol, respectively. The deterioration factors with values of Ea larger than that of TTI, ln lactic acid %, LAB, and pH, were found to be underestimated as compared to their actual levels by prediction from TTI color change, leading to potential consumption of deteriorated milk.     

Effect of milk source on the rheological properties of yogurt during the gelation process

This paper presents research on the effect of milk source on the rheological properties of curd during the gelation process of yogurt. The highest value for viscosity was exhibited by ovine milk, followed by caprine, bovine and camel milks. For bovine, ovine and caprine milk, three different transient viscosity stages were identified and described by mathematical expressions, whereas camel milk showed no significant variation in viscosity during gelation. The chemical composition of milk, namely total solids and protein content, has a major effect on the rheological properties of curd. A power law model allows the determination of the flow behaviour index and the consistency coefficient of curd made from different milk sources.     

原料牛奶中微生物的污染问题与检测分析

原料牛奶在整个生产环节中,如牛乳房微生物、挤奶环节、储存过程等都有可能发生微生物污染事件,在初始阶段乳烃素的作用下存在一段抑菌周期,经过抑菌期后原料牛奶就会出现变质现象.原料牛奶是整个乳制品供应链中的最上游,其质量安全直接影响下游的终端乳制品,是整个乳品行业能保持健康发展的基石.近年来,原料牛奶的质量安全问题已成为社会...     

Kefir粒发酵过程中牛乳体系的品质变化

为明确开菲尔粒(Kefir grains)在发酵过程中对牛乳体系品质变化的影响。本文将Kefir粒作为发酵剂应用于牛乳体系中,研究接种量、发酵时间和发酵温度对牛乳酸度、主要风味成分和流变性质的影响。结果表明,接种量、发酵温度、发酵时间对Kefir粒发酵作用的影响复杂。分析酸度变化的规律可知,相同条件下,接种量越大,酸度越高;电子鼻测定发酵乳中主要风味物质的变化发现,发酵温度越高,Kefir粒中的乳酸菌和酵母生长越快,产生风味物质的时间越短,但是菌种过快生长会导致发酵乳风味变差;流变仪测定发酵乳黏弹性、流动常数的变化可知,Kefir发酵乳的复合黏度随角频率增大而减小,储能模量G'和损耗模量G″随温度上升而增大,G'始终大于G″,tanδ始终小于1,体系呈现弹性特征。综合考虑实验结果和成本,选用在30℃条件下,接种量为0.40%的Kefir粒发酵48 h得到的酸度为86 °T,最终产品性质较为稳定,感官品质较为优良,这对Kefir发酵乳的工业化生产具有一定的指导意义。     

Physicochemical aspects of the microbiology of edible table spreads

This article describes aspects of the microbiology of edible table spreads including milk fat spreads such as butter, fat spreads of the margarine type and mixed fat spreads with fat contents ranging from 80–95% to not less than 20% by weight of the product. The water-in-oil character of these products makes a major contribution to their microbiological stability especially after they have been exposed to the micro-organisms commonly encountered in a domestic environment. The microbiological stability of edible table spreads is also influenced by the concentration and physical nature of the continuous lipid phase with product stability increasing with greater proportions of crystallized fat. Edible table spreads containing higher proportions of water are more vulnerable to microbiological deterioration. This can be controlled by ensuring a dispersed aqueous phase in the product which consists of small discrete moisture droplets stabilized against coalescence. This stabilization can be achieved by the use of increased mono- and diglyceride concentrations and/or by increasing the viscosity of the dispersed moisture droplets through the use of stabilizers, thickeners and protein. The development of unacceptable levels of microbiological deterioration during domestic use is prevented by the addition of potassium sorbate to the aqueous phase. Additive free edible table spreads with acceptable shelf-life can be manufactured by controlling the distribution of dispersed moisture droplet size and nutrient composition .