Influence of UV-A irradiation on the selected nutrient composition and volatile profiling of whole milk:Safety and quality evaluation

Aflatoxin(AF),a mycotoxin produced by several genera of fungi,is an important concern in milk-based products due to its toxicity and health consequences.The present study evaluates whether UV-A irradiation can preserve the composition of whole milk(WM)while degradaing these toxins.In addition,this study also investigates the expression of p53 proteins which can be correlated with carcinogenocity.UV-A irradiation experiments were conducted using a near collimated beam system operating at 365 nm.AFs at known concentrations were spiked in WM and irradiated at quantifiable UV doses based on the average volumetric intensity.The impact of ultraviolet light(UV-A)irradiation on volatile compounds,certain amino acids,and oxidative products were evaluated.No significant reduction in amino acids was observed except tryptophan(p<0.05).Therefore,tryptophan particularly gets degraded under UV and generates OH−radical.At 838 mJ/cm2 no significant lipid peroxidation was observed,p<0.05.The volatile profiling showed that alcohols,the key contributor of oxidized flavor was not significantly affected by the UV-A irradiation.As the overall volatile composition was comparable between the untreated and UV-A irradiated WM there may not be an adverse impact on the sensory attributes.Western blotting was used to assess the effect of UV-A irradiated WM on protein expression in HepG2 cells.Because the targeted gene p53 was not considerably altered,we can affirm that UV-A irradiated WM may be safe and not cytotoxic.Herein,the substantial breakdown of AF in WM by UV-A as well as no accumulation of toxic components from protein,lipid,and FAA degradation was observed.This study conclusively proves the performance of the UV-A LED system in degrading AF in WM below the levels recommended by Food and Drug Administration without compromising the product's quality or safety.

Antibacterial Performance of Cu-Bearing Stainless Steel against Staphylococcus aureus and Pseudomonas aeruginosa in Whole Milk

Pathogen microorganisms exist in various environments such as dairy processing facilities. They are not easily eliminated, and significantly raise the risk of bacterial contamination. The inhibition ability of a novel type 304 Cu-bearing stainless steel （304CUSS） with nano-sized Cu-rich precipitates against Staph-ylococcus aureus （S. aureus） and Pseudomonas aeruginosa （P. aeruginosa） added whole milk was investigated in this study. The results showed that after 24 h contact, the inhibition rates of the 304CUSS against S. aureus and P. aeruginosa added whole milk reached 99.2% ± 0.3% and 99.3% ± 0.2%, respectively, in contrast with the 304SS. In the plain whole milk, the inhibition rate of the 304CUSS also reached 66.9% ± 2.0% compared with the 304SS. The results demonstrated that the 304CUSS killed majority of the planktonic bacteria, and inhibited sessile bacteria adherence to the steel surface in the whole milk with and without bacteria addition, significantly reducing the bacterial growth rate. These research outcomes explicitly show an application potential of this novel antibacterial stainless steel in the dairy related food industry.

Biocontamination Risk of <i>Staphylococcus aureus</i>in Dairy Manufacturing Presence of Two Types of UHT Milk

The biofilm formation on equipment surfaces in dairy manufacturing is a major concern for industry and consumers alike, which may affect the safety and quality of dairy products. In order to identify the bio-contamination risk of materials commonly used in dairy manufacturing, adhesion of Staphylococcus aureus on glass coated by two kinds of UHT milk (whole milk and skimmed milk) was investigated. It is known that adhesion is mainly governed by surface physicochemical properties, for that, the effect of milk components on physicochemical properties of glass and bacterial surfaces were exanimated through contact angle measurements. MATLAB software was used to evaluate the ability of S. aureus adhesion on glass. The hydrophobic quantitative and electron acceptor characteristics of the glass appear to increase with the presence of fat in milk, while its electron donor property decreases with this component. The percentage of occupied surface of untreated glass was more important than in treated surfaces for 50% of the strains studied. As well, the percentage of occupied surface by bacterial strains in untreated glass by skimmed milk is generally more important compared to the whole milk. Therefore, the risk of bio-contamination of untreated glass is more favorable for bacteria cultured in skimmed milk compared to these in whole milk but the bio-contamination risk on covered glass by milk is not milk dependent and is strain dependent.

Microbial quality and associated health risks of raw milk marketed in the Tanga region of Tanzania

Objective:To evaluate micmbial quality and associated health risks of raw milk marketed in the Tanga region of Tanzania.Methods:A microbial quality assessment of marketed raw milk was undertaken by evaluating 59 samples of milk from selling points(collecting centres =15),bicycle boys(12) and kiosks/restaurants(32) in Tanga city during April-May 2005.Quality and milkborne hazards were assessed using a combination of tests in order to quantify the occurrence of Brucellosis(milk ring test),Escherichia coli(E.coli) O157:H7(culture),the coliforra bacteria as well as standard plate count(SPC).Specific gravity(SG) determination was used as an indicator of adulteration.Results:The mean coliform plate count(c.f.u/mL) of milk handled by bicycle boys(4.2×10~6) was significantly higher than that handled by collecting centres(3.0×10~6) and kiosk/ restaurants(1.4× 10~6),respectively(P 【 0.05).Of the 59 milk samples collected,33(56%) were Brucella milk ring test(MRT)-positive and 78%and 17%of the samples graded satisfactorily based on SG and coliform plate counts as prescribed by East African Community standards for raw milk.There was no verocytotoxigenic E.coli(VTEC) O157:H7 in any of the milk samples collected and analysed during the present study.Conclusions:It can be concluded that raw market milk in the study area is of poor bacteriological quality and hazardous for human consumption. This highlights the need to implement good hygiene practices and effective monitoring from production through the delivery chain to the consumer.Further studies are needed for detection of toxins that are produced by E.coli,other pathogenic spore forming bacteria(Bacillus spp.and Clostridium spp.) and other harmful microorganisms.

基于顶空固相微萃取-气相色谱-质谱法分析加速氧化过程中全脂牛羊乳粉挥发性化合物

为探究全脂牛羊乳粉在储存过程中风味物质的变化,本研究采用顶空固相微萃取-气相色谱-质谱技术对加速氧化过程中全脂牛羊乳粉挥发性化合物进行分析。研究表明,全脂牛乳粉和全脂羊乳粉中分别鉴定出56、63种挥发性物质,主要为酸类、醇类、羰基类、酯类、芳香族类、杂环类等挥发性化合物。通过主成分分析和聚类热图分析,在全脂牛羊乳粉中筛选出10种显著性差异挥发性化合物,全脂牛乳粉在储存过程中丁酸相对含量降低,2-壬酮、1-氯戊烷相对含量升高;全脂羊乳粉中壬醛、辛酸、丙酸、丁羟甲苯相对含量降低,苯甲醛、2-庚酮、烯丙基正丙酯相对含量升高。

高压射流磨在无添加全豆豆乳加工中的应用研究

本文研究了高压射流磨在无添加全豆豆乳中的应用及对全豆豆乳稳定性的影响。通过不同加工工艺下全豆豆乳的显微镜镜检、离心沉淀率、粒径分布、Zeta电位、外观口感、Lumisizer稳定性扫描为指标,明确了高压射流磨可以彻底粉碎全豆组织,降低产品粒径至33μm,且能大幅度提升无添加全豆豆乳的产品口感和货架期稳定性;同时通过考察不同蛋白质含量下全豆豆乳的弹性模量、Lumisizer稳定性扫描结果和Turbiscan扫描发现,蛋白质含量对全豆豆乳的稳定性也有影响,当蛋白质含量达到3.5%,全豆豆乳口感优、稳定性好,属于制备全豆豆乳的优选方案。由此可知:高压射流磨工艺是加工无添加全豆豆乳的关键工艺,对提高该类产品的整体稳定性、改善该类产品的质地口感、提升该类产品的整体品质有显著效果。

新疆特色驴乳产业化发展现状与对策

新疆具有发展驴乳产业得天独厚的优势条件。在新疆自贸区的设立及加快农业强区建设背景下,新疆特色驴乳产业迎来新的发展机遇。本文对近年来新疆驴乳全产业链发展现状进行梳理总结,发现新疆驴乳产业面临驴种质资源创新利用不足、泌乳性能不突出且质量参差不齐、规模化的饲养标准与规范缺失、高端驴乳产品开发程度低等瓶颈。鉴于此,本文从驴的种质资源、饲养繁殖及产业融合等方面提出了促进新疆特色驴乳业高质量发展的思路及对策。

基于响应面法优化双酶同步酶解的全豌豆乳的稳定性及营养特性研究

豌豆作为一种大宗豆类,具有营养价值高及低致敏性等特点,但全豌豆乳体系易絮凝失稳,限制其在食品中的应用。本文以脱皮豌豆为原料,采用高压均质耦合生物酶解(中温α-淀粉酶和纤维素酶)处理,通过离心沉淀率等指标,以及Box-Behnken设计优化酶解工艺条件,揭示最优工艺下全豌豆乳的稳定性和营养特性变化规律。结果表明,相较于传统过滤、单一酶解、双酶分步酶解等方法,中温α-淀粉酶和纤维素酶双酶同步酶解制备的全豌豆乳稳定性更优,最佳的酶解工艺参数为:中温α-淀粉酶:纤维素酶为4.5:5.5(酶活力比,U/g淀粉),添加总量为12 U/g,酶解时间为65 min,该条件下制得的全豌豆乳的离心沉淀率最低(27.70%),在不经过滤和不添加稳定剂的情况下,贮藏60 d内无明显的沉淀分层。与传统单体营养素复配工艺得到的豌豆乳相比,该优化工艺下制得的全豌豆乳稳定性显著提高,淀粉的消化程度降低了12.74%,蛋白质的消化程度提高了16.41%。研究结果为浓浆类的植物乳开发提供一定的理论指导。

基于残差网络模型的速溶全脂奶粉分散性与堆积密度检测方法

针对传统的奶粉品质国际标准检测方法中存在的主观性和滞后性等问题,本研究提出了一种基于残差网络(residual network,ResNet)的奶粉分散性和堆积密度的快速分类检测方法。在本研究中,使用的数据集包括499张在10倍光学显微镜下拍摄的速溶全脂奶粉颗粒微观分布图像,这些图像来自10个不同的样本组。首先,按照国际标准方法检测这10组样本的分散性和堆积密度,进而基于测试结果划分不同的分散性和堆积密度级别。随后,利用这些微观图像对ResNet模型进行训练,以实现对不同样本的有效分类。最终,通过分类结果预测速溶全脂奶粉的分散性、松散密度和振实密度。此外,本研究还对比了ResNet、EfficientNetV2和SwinTransformer等不同深度学习模型的预测效果。结果表明,基于ResNet152的深度学习模型在预测速溶全脂奶粉的分散性、松散密度和振实密度方面表现最佳,其在测试集上的准确率分别达到97.50%、98.75%和95.00%。这些深度学习模型在奶粉品质检测中的出色性能不仅证明了该方法能够实时、准确地预测奶粉的分散性和堆积密度,同时也为奶粉品质的在线检测提供了新的技术途径。

生牛乳中耐甲氧西林金黄色葡萄球菌全基因组序列分析

目的了解生牛乳中耐甲氧西林金黄色葡萄球菌(methicillin-resistant Staphylococcus aureus,MRSA)的全基因组序列特征,分析其耐药基因和毒力基因的分子特征差异。方法采用全自动微生物鉴定药敏分析仪进行细菌鉴定;通过肉汤微量稀释法进行药物敏感性检测;利用生物信息学工具对全基因组测序结果进行分子特征分析。结果SJ23319菌株和SJ23506菌株经鉴定均为MRSA;SJ23319菌株耐药谱为OXA-PEN-FOX,SJ23506菌株耐药谱为OXA-PEN-FOX-CC,耐药基因分析结果显示两个菌株均携带耐药基因mecA和blaZ,这与耐药表型结果基本一致;2个菌株染色体基因组大小、结构和功能蛋白相似,SJ23319菌株为ST59-t437-SCCmecIVa型,SJ23506菌株为ST398-t034-SCCmecV(5C)型;2个菌株功能蛋白均分布于21个直系同源簇(cluster of orthologous group,COG)条目中,携带13种相同的耐药基因,SJ23319菌株还携带有四环素类耐药基因tet(K);2个菌株携带毒力基因多达67种,SJ23319菌株携带更多的细菌黏附相关基因(fnbA/B、sdrD/E)和外毒素基因(Seb、Selk、Selq、set16-26)。结论SJ23319(ST59)菌株比SJ23506(ST398)菌株携带更多的耐药基因和毒力基因,致病性更强,进一步证明在牲畜相关的MRSA(livestock-associated MRSA,LA-MRSA)菌株中,ST59型比ST398型更容易导致社区流行和感染,应当在MRSA流行监测中更加重视。

基于图像分析技术的全脂奶粉品质软测量模型构建

针对传统奶粉品质检测方法的主观性和滞后性问题,该研究利用奶粉的加工条件和颗粒形态构建了一个基于图像分析技术和人工智能算法的奶粉品质软测量模型,用于准确、实时地预测速溶全脂奶粉的分散性和溶解性这2个重要品质性能。利用显微数码摄像头和图像处理技术,获取了奶粉颗粒的形态参数。同时,利用重采样技术解决了奶粉工厂原始数据集中的数据不平衡问题。根据实验获取的奶粉颗粒形态参数和奶粉工厂提供的奶粉生产时的加工条件数据,选用偏最小二乘模型和人工神经网络模型构建了速溶全脂奶粉分散性和溶解性的软测量模型,并利用原始数据验证了所构建模型的准确性。结果表明,用于预测奶粉分散性和溶解性所构建的偏最小二乘模型的Q^(2)和R^(2)分别为Q^(2)=0.72,R^(2)=0.94和Q^(2)=0.85,R^(2)=0.95,而用于预测奶粉分散性和溶解性所构建的人工神经网络模型的R^(2)分别为0.97和0.96。模型的良好性能证明,这些模型可以准确、实时地预测奶粉的分散性和溶解性,并为奶粉品质的在线检测提供了新的方法。

冷冻浓缩乳和全脂乳粉的营养成分对比分析

为比较冷冻浓缩乳与全脂乳粉营养成分的差异,对免疫球蛋白(immunoglobulin,Ig)、乳铁蛋白、维生素及代谢组学变化进行测定。结果表明:冷冻浓缩乳组IgA、IgG、乳铁蛋白、B族维生素、VA、VD和VC含量显著高于全脂乳粉组;分析非靶向代谢组学数据发现,冷冻浓缩乳组与全脂乳粉组的主要差异物被注释到氨基酸代谢合成、肽类代谢合成和碳水化合物代谢合成的多条关键通路中,主要是异亮氨酸、左旋水苏碱、脯氨酰-酪氨酸、肌酸、D-脯氨酸、L-谷氨酸、L-精氨酸、不对称二甲基精氨酸、L-哌可酸、L-组氨酸、N-甲基-L-谷氨酸等氨基酸和小肽类物质和麦芽四糖、海藻糖、D-麦芽糖、异麦芽糖等碳水化合物类代谢物,它们的相对表达量在冷冻浓缩乳组显著高于全脂乳粉组(P<0.05)。本研究结果表明,冷冻浓缩乳在营养成分上显著优于全脂乳粉。

发芽处理对全豆豆奶品质的影响

本文利用经发芽处理和未经发芽处理的大豆制备全豆豆奶,对比研究其理化特性、抗营养因子和抗氧化活性。结果表明,经发芽处理的全豆豆奶的蛋白质含量从3.04 g/100 g提升到3.43 g/100 g,总膳食纤维含量从1.31 g/100 g提升到1.43 g/100 g;胰蛋白酶抑制剂活性和植酸含量显著降低(P<0.05),抗氧化活性显著增强(P<0.05)。说明大豆发芽处理是一种低廉、绿色环保的能够改善大豆、全豆豆奶品质和营养价值的方法。

牛奶红薯全粉窝窝头的配方及制作工艺研究

窝窝头是日常生活中常见的面食产品,传统的窝窝头存在口感偏硬、易掉渣等缺点。为解决这些问题,在传统窝窝头的配方中添加了牛奶,即以红薯全粉和面粉为原料,以牛奶替换配方中的部分水制作红薯全粉窝窝头。通过感官评价和质构特性检测,在单因素试验结果的基础上,通过正交试验优化工艺及配方,并综合评价牛奶红薯全粉窝窝头的品质。结果表明,牛奶红薯全粉窝窝头的最佳制作工艺及配方为:红薯全粉125 g,小麦粉125 g,水150 g,酵母2 g,牛奶98 g,白糖15 g,发酵时间40 min。在此条件下制作的牛奶红薯全粉窝窝头的感官评分为91.3分,其口感绵软,弹性适中,品质最佳。通过研制牛奶红薯全粉窝窝头,改善了窝窝头的品质,丰富了窝窝头的种类。

吉林地区奶源金黄色葡萄球菌耐药性及遗传特征分析

目的了解鲜牛乳中金黄色葡萄球菌(Staphylococcus aureus,S.aureus)流行情况及耐药情况、分子特征和遗传特征。方法细菌分离培养及聚合酶链式反应(polymerase chain reaction,PCR)鉴定S.aureus,K-B药敏纸片扩散法检测其耐药性,对其中44个分离株进行全基因组测序(whole genomic sequence,WGS),并分析分子特征及遗传特性等。结果共分离出214株S.aureus,对13种常用抗生素均有耐药性,对青霉素产生耐药性菌株最多(145/214,67.76%)。44个流行株中,耐药表型达31种,25个菌株有多重耐药;检测到β-内酰胺类、四环素类等12类耐药基因及季铵盐类消毒剂耐药基因,其中6株检测到耐利奈唑胺基因;L8株携带11种毒力基因,至少90%的流行株携带aur、hlgA/B/C基因毒力;ST9-t899是流行优势型。SNP-WGS全基因组遗传进化分析,提示有人、畜间互传可能性。结论吉林地区牛场样本中S.aureus流行率为42.80%,存在多重耐药,且耐药谱广、耐药表型多样;有人畜间传播可能。鲜牛乳作为初级食品,对其中S.aureus特别是耐甲氧西林金黄色葡萄球菌耐药性及分子特征监测,是对食品卫生及公共卫生安全的重要保障。

以全蛋为原料制备双蛋白发酵乳工艺优化

采用单因素试验和正交试验法研制双蛋白发酵乳。结果表明:鸡蛋酶解液、豆浆、牛奶体积比为1∶3∶1时效果较好;蔗糖添加量为7%(质量分数)、发酵菌接种量为10%、发酵温度为43℃、发酵时间5 h时制备发酵乳感官评分较高,为90.68±0.11。向双蛋白发酵乳中添加D⁃异抗坏血酸钠0.10%、β⁃环糊精0.20%、羧甲基纤维素钠0.15%、卡拉胶0.10%时制得成品,感官评分较高,为95.42±0.45。产品理化分析结果为持水率(57.45±0.06)%,酸度(83.67±0.57)°T,脂肪含量(2.66±0.04)g/100 g,非脂肪固体含量(9.22±0.06)g/100 g,蛋白质含量(2.60±0.01)g/100 g,多肽含量(0.45±0.01)mg/g,符合GB 19302—2010《食品安全国家标准发酵乳》要求。

巴氏灭菌与超高温灭菌对全脂牛乳挥发性风味物质的影响

采用顶空固相微萃取分别对原料全脂牛乳、巴氏灭菌全脂牛乳和超高温灭菌全脂牛乳的挥发性成分进行萃取,经气相色谱-质谱联用仪分析。结果显示,原料全脂牛乳中共鉴定出12种挥发性物质,主要包括酸类和烷烃类;巴氏灭菌全脂牛乳中共鉴定出17种挥发性物质,主要包括酸类、酯类、酮类和烷烃类;超高温灭菌全脂牛乳中共鉴定出17种挥发性物质,主要包括酸类、酮类和烷烃类。经数据统计分析,3种牛乳样品的挥发性组分呈现明显差异。

SDE与SAFE分析全脂巴氏乳挥发性成分

采用同时蒸馏萃取与溶剂辅助风味蒸发法萃取分析巴氏全脂乳的挥发性成分,用气相色谱-质谱联用(GC-MS)对挥发性成分进行了分析。结果表明同时蒸馏萃取法以二氯甲烷为萃取溶剂时鉴定出8种成分,以乙醚为萃取溶剂时鉴定出6种成分;溶剂辅助风味蒸发法鉴定出8种,两种方法共计鉴定出14种挥发性成分,其中酸类8种、醛类1种、醇类2种、酯类2种、其它类1种,其中含量较大的有己酸、辛酸、癸酸、月桂酸、肉豆蔻酸等。

水分活度对全脂羊奶粉贮藏期间脂肪稳定性的影响

采用加速氧化的方法研究水分活度对全脂羊奶粉贮藏期间脂肪稳定性的影响。通过测定全脂羊奶粉的酸值、过氧化值、硫代巴比妥酸值(TBA)、颜色等指标评价全脂羊奶粉贮藏期间的氧化状况。结果表明,水分活度为0.32的全脂羊奶粉贮藏期间酸值、TBA值显著高于水分活度为0.11和0.23的全脂羊奶粉(p<0.05),且水分活度为0.32的全脂羊奶粉过氧化值变化速率较快(p<0.05),且褐变严重。因此,降低全脂羊奶粉的水分活度可以提高其贮藏稳定性。

全乳添加小麦粉对荷斯坦公犊牛的屠宰性能及肉质的影响

对初生体重相近的20头荷斯坦公犊全乳饲喂至35日龄后,随机分为继续饲喂全乳的对照组和全乳中添加2%、4%和6%小麦粉的试验组,至90日龄进行测定,研究了对荷斯坦公犊的屠宰性能和肉质的影响。结果表明:在全乳中添加小麦粉可显著提高荷斯坦公犊的宰前活重、胴体重、净肉重、胴体产肉率和眼肌面积(P<0.05),提高了肌肉的嫩度和脂肪含量(P<0.05),且屠宰性能与肉质的改善效果随着小麦粉添加比例的增加而提高。因此,全乳中添加6%以内的小麦粉,既提高了屠宰性能,又能改善肉质。