一种快速提取乳粉中脂肪测定过氧化值的研究探讨

现研究一种快速提取乳粉中脂肪测定过氧化值的方法.通过优化乳粉中脂肪的提取条件,包括加热温度、加热时间和固液比等影响乳粉中脂肪提取的关键因素点,选择固液比为1:2,60℃加热15 min后提取脂肪测得过氧化值数据可靠,并验证方法的可行性.本研究建立的这种快速提取乳粉中脂肪测定过氧化值的方法,可用于预测乳粉货架期内过氧化值...     

颗粒度对乳粉品质稳定性的影响

目的通过建立乳粉感官评价体系和理化指标评价体系两个评价方法来反映乳粉的品质稳定性,从而综合评定乳粉颗粒度对乳粉品质稳定性的影响。方法乳粉的感官主要从乳粉的气味、冲调液的滋味和气味方面进行感官评定。乳粉的理化评价体系主要考察乳粉的表面油含量、酸值及过氧化值。结合感官评价体系和理化评价体系的结果,调整乳粉生产工艺,选择最佳的乳粉颗粒度。结果乳粉的颗粒大小、脂肪的存在形态影响乳粉的品质稳定性。结果表明乳粉颗粒越大,其品质稳定性相对越高。结论综合感官及理化指标,颗粒度与乳粉的感官及品质稳定性呈正相关:乳粉的颗粒越大,感官得分越高,理化指标(表面油含量、酸值及过氧化值)越低,乳粉的品质稳定性越好。     

超声波技术在配方乳粉过氧化值检测前处理中的应用

为测定配方乳粉过氧化值,以三氯甲烷、甲醇作为萃取剂,辅助超声波技术提取配方乳粉中的脂肪。采用正交优化法,确定配方乳粉过氧化值测定中样品前处理的最佳工艺条件为:超声功率60%、液固比11:1(v/w)、第一次超声时间5 min、第2次超声时间25 min。在此基础上,利用比色法比较不同前处理方法对乳粉过氧化值测定的影响。结果表明,超声波处理法对配方乳粉中脂肪的二次氧化影响程度比碱性乙醚法小,而且操作简便,有机溶剂用量少。     

乳粉制品中脂肪过氧化值测定方法的研究

阐述了乳粉制品中脂肪过氧化值的测定方法;比较了提取脂肪时试样经干燥和未经干燥对过氧化值的影响;比较了不同提取溶剂对过氧化值的影响。结果表明,在提取脂肪时试样不需要进行干燥,采用石油醚做提取溶剂。     

不同添加量ARA及DHA在婴幼儿乳粉中的稳定性研究

采用55℃加速方法对不同添加量的ARA和DHA婴儿配方乳粉进行了稳定性实验,研究了不同添加量的ARA和DHA婴儿配方乳粉的过氧化值、ARA及DHA含量、色泽及气滋味的变化情况。研究结果显示,不同添加量的ARA和DHA婴儿配方乳粉的这些检测指标在加速实验中没有明显差异,为在婴儿配方乳粉中提高ARA和DHA添加量的可行性提供了一定的理论支持。而且该方法较传统的常温货架期实验能更快速地评估乳粉的稳定性。     

DHA/AA在婴幼儿配方乳粉添加中氧化稳定性的研究

研究针对二十二碳六烯酸(DHA)和花生四烯酸(AA)是现在婴幼儿乳粉中营养强化剂添加的重点,这2种成分对婴幼儿的健康成长和发育起着重要的作用,但这2种不饱和酸极易被氧化,选择稳定性好的产品是决定乳粉品质的重要因素。对市售的5个厂家的二十二碳六烯酸(DHA)和花生四烯酸(AA)微胶囊产品进行了过氧化值(POV)的测定,分析DHA和AA在婴儿配方乳粉中稳定性。     

乳粉掺伪的吸光光度法检测

长期以来,乳粉因其易于消化吸收,营养价值高,是人们极为喜爱的食品,但乳粉和乳一样也是一种可进行伪造的食品,可以掺伪,也可以抽减其成分。近几年来,发现有些乳粉中掺有一定比例的豆粉,其结果不但影响产品质量,也降低了乳粉的营养价值。目前国内乳的掺伪检验方法报导很多,但对乳粉中掺伪的检验方法仅仅限于几种定性检验,本方法运用紫外分光光度计,对待测样品进行处理后进行测定,其方法简单易行,灵敏度高,检验结果准确,本文就检验方法做以介绍,仅供同行参考。1方法原理在乳粉中的掺伪物质主要是经过高技术处理（脱腥）的优质豆粉,因豆粉是属豆类植物果实产品,内含有定量的皂素,而纯乳粉不含皂素,利用皂素与浓氢氧化钠反应生成     

婴幼儿配方乳粉贮存过程中品质劣变的研究进展

婴幼儿配方乳粉富含脂肪、蛋白质和碳水化合物,在贮存过程中易发生品质劣变,如脂质氧化、非酶褐变和乳糖结晶,而降低其营养价值。文中对婴儿配方乳粉贮存过程中品质劣变的类型、影响因素和研究方法进行了概述,并对婴幼儿配方乳粉劣变反应的研究方向进行了展望。     

基于Real-time PCR法检测乳粉中牛源性成分定量研究

基于Real-timePCR建立了乳粉中牛源性成分相对定量检测方法,并对牛的特异性引物与探针进行了特异性、灵敏度和稳定性测试。通过模拟不同浓度牛乳粉与马乳粉混合样本,根据其△Ct值的函数关系进行线性拟合进而绘制标准曲线,建立乳粉中牛源性成分的相对定量检测。结果显示,该方法的最低检测限为0.000 01 mg/mL,回收率为91.11%～119.2%,组间变异系数≤0.58%、组内变异系数≤1.44%。说明该方法在特异性与稳定性上适用于乳粉中牛源性成分及含量的掺假检测。     

一种羊乳粉的微滴式数字PCR定量分析方法

基于市场上对乳品溯源技术的迫切需求,以微滴式数字聚合酶链式反应技术对羊乳粉中的乳源进行准确判别。基因检测技术对判别乳源来源方面克服了成分复杂、检测时间长等的缺点,更加精准地针对本源进行检测,减少了误判的可能性。本实验以羊乳粉质量、DNA质量浓度及其拷贝数为实验指标,建立了以羊乳粉拷贝数与质量的关系式,准确地判断出羊乳粉的质量,其公式为M=（C－4.75）/3.56,其中,M代表羊乳粉的质量（mg）,C代表每微升的拷贝数（copies/μL）,该方法的建立对现有市场上的羊乳粉定量检测提供了新的方法和思路。     

基于多指标综合评分法优化棕榈油粉末油脂及其奶片制品配方

目的 优化棕榈油基粉末油脂和棕榈油基奶片的配方。方法 将棕榈油喷雾干燥成粉末状,然后和其他成分一起被压制成片剂。采用主成分分析法对棕榈油粉末油脂的包埋率、溶解度、水分含量、酸价和过氧化值进行了评价,并采用熵权法对棕榈油基奶片进行了评价。结果 所制得的棕榈油粉末油脂和棕榈油基奶片其强制对比法-熵权法综合感官评分分别为91.03±0.29和91.97±0.46。棕榈油粉末油脂的最佳工艺配方为: 棕榈油添加量42%、脱脂奶粉添加量18%、麦芽糊精添加量28%和复合乳化剂添加量4.5%; 棕榈油基奶片最优配方为: 最棕榈油粉末油脂添加量为10%、脱脂奶粉添加量为46%、复合糖粉添加量为15%、复合改良剂添加量为27%。结论 通过单因素和正交试验分别对棕榈油基粉末油脂和棕榈油基奶片的配方进行优化后,所制得的棕榈油粉末油脂呈松散的乳白色,无异味,无结块和杂质;棕榈油基奶片呈乳白色,色泽分布均匀,无明显斑点,口感细腻爽滑、甜味适中、有咀嚼感;产品内质结构均匀,硬度适中,无明显分层现象。     

Comparative study on the characteristics and oxidation stability of commercial milk powder during storage

The quality of milk powder can decrease during storage. In this study, the characteristics of 12 kinds of commercial milk powder from China were investigated. Changes in various indicators were tracked to comprehensively estimate the oxidation stability of different commercial milk powders. The components of the commercial milk powder were different. The percentages of milk fat, protein, and carbohydrates ranged from 9.8 to 28.5 g/100 g, 15.0 to 24.0 g/100 g, and 32.0 to 67.5 g/100 g, respectively. The water activities ranged from 0.2394 to 0.5286. The diameters of the milk fat globules in different commercial milk powder ranged from 13.99 to 41.09 nm. At the same time, the peroxide value of the control sample was low (≤0.14 mEq/kg). After 3 mo of storage, the peroxide values of some of the commercial milk powder increased significantly. The changes in the thiobarbituric acid values during storage did not follow a common trend. The contents of free fat in the different control samples were 0.21 to 1.67 g/100 g, and these values did not increase during storage. After 3 mo of storage, the hydroxymethyl furfural values and b color values of the different commercial milk powder reached their highest levels. The concentrations of typical oxidized flavor compounds in different commercial milk powder increased greatly with prolonged storage time. The level of hexanal was the highest, and the contents in all the samples ranged from 28.56 to 4,071.28 μg/kg after 6 mo of storage and from 5.91 to 6,281.37 μg/kg after 12 mo of storage. Free radicals were found in some of the stored milk powder, and these were shown as single peaks or multiple peaks. The ratios of the peak areas and masses reached 12.42 × 10⁶ to 14.26 × 10⁸. However, the presence of free radicals in the commercial milk powder was not consistent. The water activities and diameters of the fat globules in the commercial milk powder were highly correlated with their oxidation stabilities during storage.     

原生态与人工添加二十二碳六烯酸羊乳制品贮藏期脂肪酸稳定性比较

通过饲喂奶山羊富含二十二碳六烯酸（docosahexaenoic acid，DHA）的微藻粉，获得原生态DHA羊乳（DHA含量为30 mg/100 g原料乳），然后将其制作成超高温瞬时灭菌（ultra-high temperature instantaneous sterilization，UHT）乳及全脂乳粉，同时设立人工添加富含DHA微胶囊粉的UHT乳及全脂乳粉作为对照组，在常温（25 ℃）和高温（37 ℃）下进行为期28 d的贮藏实验，研究原生态与人工添加DHA羊乳制品贮藏期脂肪酸稳定性。结果表明，与人工添加组相比，贮藏期间原生态UHT乳及全脂乳粉的DHA含量下降速率明显减缓，在UHT乳中，人工添加组乳制品DHA含量降低率在37 ℃下最高达（40.92±3.52）%（贮藏第28天），此时原生态组DHA降低率为（36.70±4.84）%。贮藏期间，原生态与人工添加DHA的UHT乳及全脂乳粉中多不饱和脂肪酸相对含量总体均下降，且与人工添加DHA的乳制品相比，原生态组中多不饱和脂肪酸相对含量更高，更易氧化生成碳链更短的脂肪酸。此外，随着贮藏期的延长，原生态DHA乳制品组中的油脂氧化指标过氧化值和酸价上升速率明显低于人工添加DHA乳制品组。综上，本实验可为制备富含DHA的天然奶制品提供理论参考。     

Shelf life prediction of aluminum foil laminated polyethylene packed vacuum dried coconut milk powder

Shelf life of vacuum dried coconut milk powder packed in aluminum foil laminated polyethylene packages was predicted using developed mathematical models based on two limiting criteria viz., onset of caking and lipid oxidation. Accelerated storage studies for coconut milk powder packed in aluminium foil laminated polyethylene pouches were conducted at 90 ± 1% relative humidity and 38 ± 2 °C temperature. Threshold value for the shelf life prediction based on moisture migration was taken as the critical moisture content at which lump formation was observed. Shelf life prediction based on lipid oxidation involved establishing relationships between rate of oxygen absorption, package oxygen concentration, volume of O₂ absorbed, peroxide value of the powder and storage time. A peroxide value of 10 mEq. of O₂ per kg fat was considered as the threshold limit for oxidative rancidity. A good fit between experimental and predicted data with relative deviation percent below 10% was observed during storage studies.     

Storage stability of coconut milk powder

Spray-dried coconut milk powder prepared with additions of skim milk and dextrin was stored in packages for 6 months at room temperature (30°C and 80% RH). The packaging materials used were aluminum laminate (vacuum and air packed) and polypropylene. The sorption isotherm of the powder showed that the monolayer of water molecules was complete when the relative humidity was 27% which corresponded to a moisture content of 5%. Measurements of water activity, moisture content, peroxide value and solubility index indicated that lipid oxidation is the limiting factor in the stability of the powder. Its maximum shelf-life was 4 months when air or vacuum packaged in aluminum laminates and 1 1/2 months in polypropylene.     

Fish oil microencapsulation as influenced by spray dryer operational variables

The effects of spray‐drying air temperature, aspirator rate (drying air mass flow rate), peristaltic pump rate (feed mass flow rate) and spraying air mass flow rate on microencapsulation properties of fish oil including moisture content, particle size, bulk density, encapsulation efficiency and peroxide were investigated. The process was carried out on a mini spray dryer, and skim milk powder was used as the encapsulating wall material. Results indicated that increasing inlet air temperature increased the particle size, encapsulation efficiency and peroxide value but decreased the bulk density and moisture content of product. Increasing aspirator rate resulted in increased particle size and peroxide value but decreased the moisture content and bulk density. Increase in feed mass flow rate increased the moisture content, particle size, bulk density and peroxide value but decreased the encapsulation efficiency of microcapsules. The encapsulation efficiency and bulk density increased with the increasing aspirator rate but moisture content, particle size and peroxide value decreased.     

牛、羊乳粉的DSC热学性质比较及掺假分析

为明确羊乳粉、牛乳粉的热学特征,采用差示扫描量热法（differential scanning calorimetry,DSC）对真空冷冻干燥制备的全脂羊、牛乳粉样品以及高比例掺假（75%、50%、25%）和低比例掺假（10%、5%、3%、1%）牛乳粉的混合羊乳粉样品进行热力学分析。结果表明,全脂羊乳粉和全脂牛乳粉在DSC热学指标上存在差异,全脂牛乳粉相比全脂羊乳粉缺失一个脂肪特征熔融吸热峰b,蛋白质熔融吸热峰c峰值温度和热焓值较低,而乳糖熔化分解峰e热焓值较高。对于掺入不同比例牛乳粉的羊乳粉,通过检测是否存在吸热峰b及其热焓值,可判断样品掺假牛乳粉比例是否在25%以下及判断掺入牛乳粉的量;在不同比例掺假样品中检测乳糖熔化分解峰e的焓值可判断羊乳粉掺入牛乳粉的掺假量。因此,DSC技术可以实现对羊乳粉、牛乳粉热学性质的分析和评价,也可作为乳制品行业质量保证和真实性鉴别的潜在分析工具。     

Influence of Wall Material and Inlet Drying Air Temperature on the Microencapsulation of Fish Oil by Spray Drying

Several single and composite milk-originated wall materials were used to microencapsulate fish oil via spray drying at various inlet drying air temperatures. Skim milk powder (SMP), whey protein concentrate, whey protein isolate (WPI), 80% WPI?+?20% milk protein concentrate, and 80% WPI?+?20% sodium caseinate (NaCas) were applied as the wall for capsules generated at drying air temperatures of 140, 160, and 180 °C. The higher the drying air temperature, the higher was the particle size, encapsulation efficiency, and peroxide value and the lower was the moisture content and bulk density. The microcapsules prepared with SMP showed the highest encapsulation efficiency and lowest peroxide value for the oil due to the presence of lactose in its chemical composition. Differential scanning calorimetry and Fourier transform infrared analyses indicated the absence of any significant interaction between SMP and fish oil.     

冷冻调理马铃薯饼加工技术的探讨

对马铃薯的预糊化实验结果揭示,在各种加热方法中,马铃薯经蒸煮25min后的糊化效果最好.正交试验结果表明,奶粉含量和黄油含量对冷冻调理马铃薯饼的感官指标有高度显著的影响.对冷冻调理马铃薯饼的油脂的测试结果显示,未经油炸的马铃薯饼的脂肪含量为4.24%,而经过油炸后的马铃薯饼的脂肪含量为11.18%.经过一个月的冻藏后,未经油炸的冷冻调理马铃薯饼的油脂的过氧化值为1.94%,而经过油炸的冷冻调理马铃薯饼的油脂的过氧化值为7.79%.