不同乳糖酶酶学特性比较及在无乳糖原料奶生产中的应用

以3 种乳糖酶为研究对象,研究其酶学特性,并应用于无乳糖原料奶的生产。采用聚丙烯酰胺凝胶电泳法分析乳糖酶的成分及分子质量;邻硝基苯酚β-D-半乳糖苷法测定乳糖酶活力;用电子鼻检测原料奶储存过程中气味的变化。结果表明：酶A的等电点为4.0和5.0,酶B为5.0,酶C为3.0;酶A在40 ℃和pH 6.5时酶活最高,酶B在35 ℃和pH 6.5时酶活最大,酶C在45 ℃和pH 5.0时活力最高。电子鼻检测结果表明,在4～10 ℃储存12 h,原料奶气味无显著性差异。在4～6 ℃条件下,添加6 000 U/g乳糖酶A在5～6 h内可将原料奶中乳糖水解至0.5%以下;添加6 000 U/g乳糖酶B在8～9 h将原料奶中乳糖水解至0.5%以下。因此,乳糖酶A和酶B为中性乳糖酶,乳糖酶C为酸性乳糖酶;生产无乳糖原料奶采用中性乳糖酶A较好。     

pH对高效液相色谱法测定保健食品中维生素B12含量结果的影响

摘 要： 目的通过高效液相色谱法研究原料中包含较高含量碳酸钙的复合维生素片且样品溶液pH>7.0不同pH条件下维生素B12 检测结果的差异性并探究其原因。方法 选取原料中添加较高含量碳酸钙且样品溶液pH>7.0的复合维生素片,调节样品溶液pH为4.0~4.5、5.0~5.5、6.0~6.5时测定样品中维生素B12的含量并记录;检测并记录pH分别为4.02、5.01、6.05水稀释得到的标准中间液维生素B12的检测结果. 记录并分析pH为4.0~4.5、5.0~5.5、6.0~6.5的样品和碳酸钙溶液60min内pH的变化。结果不同pH样品溶液维生素B12测得的结果值有显著性差异,调节pH为4.20~4.50时测得的结果值与样品实际结果值相符;维生素B12标准中间液在不同pH下测得的检测结果相同。样品和碳酸钙溶液的pH在60 min内随着时间的变化发生改变,调节溶液pH>5.0时,溶液的酸碱性较不稳定,在10~20 min内溶液会由酸性变为碱性;调节溶液pH<5.0时,溶液在60 min内较稳定始终为酸性,碳酸钙溶液的酸碱性与样品溶液有相同的变化趋势。结论在保健食品维生素B12的检测中需要关注样品中原辅料的种类和配比对样品溶液检测过程中酸碱性的影响,对原料中含较高含量碳酸钙且样品溶液pH>7.0的样品在维生素B12检测中需用柠檬酸调节溶液pH为4.2~5.0之间。     

高效液相色谱法同时测定保健食品中泛酸、烟酰胺、维生素B1、维生素B2、维生素B6的含量

目的建立高效液相色谱法同时测定保健食品中泛酸、烟酰胺、维生素B_1、维生素B_2、维生素B_6的含量。方法样品经0.2%磷酸溶液超声提取,经Alltima-C18柱分离,以乙腈-5 mmol/L庚烷磺酸钠溶液为流动相进行梯度洗脱,采用二极管阵列检测器(diode array detector,DAD)同时在200 nm、280 nm波长处进行检测。结果泛酸、烟酰胺、维生素B_1、维生素B_2、维生素B_6能实现较好的分离,在各自线性范围内线性关系良好,平均回收率为93.9%~103.2%,相对标准偏差(relative standard deviation,RSD)为0.4%~1.8%。结论该方法操作快速简便、精密度和重复性好,可适用于保健食品中泛酸、烟酰胺、维生素B_1、维生素B_2、维生素B_6含量的同时测定。     

Effect of storage on the vitamin B6 activity of foods (author's transl)

In a study of the effect of storage on the vitamin B6 activity of foods, the vitamin B6 content of different foods of plant and animal origin and also of a mixed feed with added pyridoxine were analyzed microbiologically using Saccharomyces carlsbergensis as test organism. Vitamin B6 activity was determined initially, in some of the specimens after storage for 10 months and again in all foods after 40 months. The storage period of 10 months caused a loss of the natural vitamin B6 content of about 25--30%. This loss increased to more than 50% after 40 months storage. The diet containing the high level of synthetic pyridoxine lost 85% of its vitamin B6 content.     

Heat treatment for the control of Bacillus cereus spores in foods

The effect of heat treatments on food products related to soybean curd contaminated with Bacillus cereus spores was investigated for the purpose of preventing food-poisoning outbreaks by B. cereus. In the case of B. cereus strains isolated from foods, heating foods inoculated with the spores for 20 min at 70 degrees C, 5 min at 75 degrees C, 2 min at 100 degrees C, or 10 sec with a microwave oven plus reheating after standing for 2 hr at 25 degrees C reduced the number of surviving cells within the foods to less than one-hundredth. In the case of a heat-resistant strain isolated from a food poisoning outbreak, heating for 20 min at 70 degrees C plus reheating after standing for 1.5-2 hr at 35 degrees C, heating for 10 min at 75 degrees C plus reheating after standing for 1.5-2 hr at 35 degrees C, or heating for 2 min at 100 degrees C plus reheating after standing for 4 hr at 25 degrees C was effective. There was not much difference between the flavor components in foods with and without heat treatment at 70 degrees C, as analyzed by gas chromatography-mass spectrometry. These results indicate that these heat treatments are available to control B. cereus spores, without affecting the sensory quality of the foods.     

FOOD SOURCES OF VITAMIN B‐6 OF A GROUP OF INDONESIAN CHILDREN1

Food sources of vitamin B‐6, commonly consumed by 77 children (age =8–9 years) in Bogor, West Java, Indonesia, were analyzed for total vitamin B‐6 content using Saccharomyces uvarum, and compared with the vitamin B‐6 values of the USDA Nutrient Database for Standard Reference. The total vitamin B‐6 analyzed values for these foods (mg/100 g) were significantly lower than the USDA database values. The mean vitamin B‐6 intakes of the subjects calculated using analyzed values (0.57 pm 0.26 mg/day) were significantly lower (p<0.0001) than the mean vitamin B‐6 intakes calculated using USDA database values (0.97 pm 0.31 mg/day). Mean differences between intakes calculated by the two methods were about 70%. The contribution of vitamin B‐6 from plant foods (52%) was similar to that of animal sources (48%). Estimation of vitamin B‐6 intakes using analyzed values of the local foods more accurately represented actual intakes than database values.     

2019年广州市售食品中食源性致病菌监测结果分析

目的 了解广州市售食品中食源性致病菌污染和分布情况,以及污染危险因素。方法 2019年共采集9类共1066份食品样品,对霍乱弧菌、副溶血性弧菌、创伤弧菌、溶藻弧菌、河弧菌、金黄色葡萄球菌、沙门氏菌、克罗诺杆菌、蜡样芽胞杆菌、单增李斯特氏菌、小肠结肠炎耶尔森菌等进行监测分析。结果127份样品食源性致病菌检出阳性,检出率为11.91％。食源性致病菌中克罗诺杆菌的检出率最高(24.69％),溶藻弧菌检出率为14.81%、创伤弧菌检出率为6.76%、副溶血性弧菌检出率为5.52%。不同食品类别中甲鱼和蛙的检出率最高,达到了43.21%,其次为冲调谷物制品（25.93%）、进口生畜肉（15.97%）、生食动物性水产品（15.83%）和水产肉糜（12.50%）。不同采样场所中采自网店的食品食源性致病菌检出率最高(29.17％),其次依次是餐饮单位（21.59%）、农贸肉菜市场（15.38%）、超市（14.36%）和学校(8.72％),最低的是零售店（3.88%）。预包装食品食源性致病菌检出率（21.33%）高于散装食品的检出率（10.37%）。结论 2019年广州市部分市售食品存在较高的食源性致病菌检出率,应对重点食品加强监管,降低食品中致病菌污染,预防食源性疾病的发生。     

云南6种食用菌中维生素B1和B2的含量调查

目的 调查分析云南省6种食用菌中维生素B1和B2的含量。方法 定点采集云南省6种常见新鲜食用菌, 按GB 5009.84-2016《食品安全国家标准 食品中维生素B1的测定》和GB 5009.85-2016《食品安全国家标准 食品中维生素B2的测定》, 用高效液相色谱法测定样品中的维生素B1和B2的含量。结果 6种常见新鲜食用菌中维生素B1的含量平均值最高的是虎掌菌0.0812 mg/100 g, 最低的是干巴菌为0.0298 mg/100 g; 维生素B2含量平均值最高的是干巴菌为0.587 mg/100 g, 平均值最低的是人工种植的羊肚菌为0.0510 mg/100 g。 结论 人工种植和野生的食用菌均含有一定量的维生素B1和B2, 具有一定的营养价值。     

Effect of freezing and canning on the content of selected vitamins and pigments in seeds of two grass pea (Lathyrus sativus L.) cultivars at the not fully mature stage

Seeds of the grass pea (Lathyrus sativus L.) cultivars Derek and Krab, with a dry matter content of about 33%, were used for freezing and for canning. The content of vitamins C, B1, and B2 and of carotenoids, beta-carotene, and chlorophylls was determined in raw and blanched material, in frozen products after 6-month storage before and after cooking to consumption consistency, and in canned products after 6-month storage. In comparison with the cultivar Krab, raw seeds of Derek contained 45% more vitamin C, 14% more total chlorophylls, 13% less thiamine (vitamin B1), and 7% less riboflavin (vitamin B2). The level of carotenoids was similar. Blanching of seeds led to a statistically significant decrease only in the content of vitamin C. Freezing and frozen storage significantly lowered the level of vitamin C and chlorophylls. The cooking of frozen seeds and the production of canned products and their storage resulted in a statistically verified reduction in the content of components analysed in all the samples. Greater losses were found in products prepared from seeds of the cv. Krab. After cooking, frozen seeds contained more of all the analysed components than the canned products.     

Kinetics of free and glycosylated B6 vitamers,thiamin and riboflavin during germination of pea seeds

The effect of germination on the free and glycosylated B₆ vitamers (pyridoxine, pyridoxal, pyridoxamine and glycosylated pyridoxine), thiamin and riboflavin content in pea seed (Pisum sativum L, var Esla) was investigated. In raw peas, the total vitamin B₆ content (sum of all vitamers expressed as pyridoxine) was 2.183 mg kg⁻¹ DM. Pyridoxine was found to be the predominant B₆ vitamer, while only a little amount of glycosylated pyridoxine, the vitamer with the lowest boiavailability, was observed. Thiamin and riboflavin content in raw peas was found to be 7.614 and 2.110 mg kg ⁻¹ DM, respectively. After 6 days of germination, carried out at 20°C, in the dark and with daily rinsing, a significant increase of the total vitamin B₆ content, mainly due to the increase of glycosylated pyridoxine, was observed. The content of pyridoxal and riboflavin increased in peas 7.5 and 2 times, respectively, whereas pyridoxine, pyridoxamine and thiamin decreased by 83, 24 and 25%, respectively, at the end of the experiment. Results obtained for these vitamins during pea germination were fitted to modelling curves in order to predict vitamin content for different germination periods. © 1999 Society of Chemical Industry     

特殊医学用途全营养配方食品的稳定性研究

本试验考察了特殊医学用途全营养配方食品（适合10岁以上人群）在加速试验、影响因素（高温、高湿）试验以及长期试验（常温储藏）条件下营养素的稳定性。结果表明,在整个加速试验过程中,产品感官未发生明显变化,所有营养素均存在一定程度的衰减,90和180 d后衰减程度最高的营养素分别是维生素A （11.53%）和维生素C （30.73%）。高温试验结果表明,在60℃条件下产品感官发生了明显变化,粉体及冲调液颜色均变深,而40℃条件下感官无明显变化,两种温度条件下受温度影响较大的营养素均为维生素A、维生素C和铜。高湿试验结果表明,湿度对开封后的样品影响比较明显,而听罐（马口铁）对湿度具有较好的阻隔性。长期试验结果表明,相比于宏观营养素和矿物质,维生素类营养素的衰减程度更高,540 d后衰减程度最高的营养素为维生素C （10.68%）,720 d后维生素A （32.95%）、维生素B₁（24.32%）、泛酸（22.19%）、维生素C （21.69%）的衰减率均超过20%。本研究为特殊医学用途配方食品的研发及应用提供一定的参考。     

2种运动食品对人体运动能力的影响对比研究

以30名男性运动员为对象,通过交叉食用、自身对照的试验方式,评估2种营养组成不同的运动食品对人体运动能力、体能恢复和疲劳程度等方面的作用。试验结果表明:在空腹血糖水平相同的情况下,进食30min后运动食品A组的血糖浓度高于运动食品B组的,在强度60%最大摄氧量(VO_(2max))运动50 min后运动食品A组的血糖浓度也高于运动食品B组的。在进行力竭训练后,3,6,9,12,15min的5个时间点内,运动食品A组的血乳酸清除效率明显高于运动食品B组的。运动食品A组在进行力竭训练过程中的10个心率测定点的数值均优于其他2组的,训练结束后的10个心率测定点的数值显示运动食品A组的心率恢复情况均优于其他2组的。运动食品A组的血清睾酮/皮质醇比值较其他2组的高。在连续食用的情况下,运动食品A对人体运动能力的维持能力,提高体能水平和缓解疲劳的效果均优于运动食品B。     

紫外串联荧光检测法测定奶昔中维生素B6和烟酰胺

目的建立紫外串联荧光检测法同时快速检测奶昔中维生素B_6和烟酰胺的分析方法。方法参照GB 5009.154-2016《食品中维生素B_6的测定》和GB 5009.89-2016《食品中烟酸和烟酰胺的测定》,采用带有紫外检测器和荧光检测器的高效液相色谱仪快速检测奶昔中维生素B_6和烟酰胺。结果该方法的准确度偏差15%,线性相关系数0.99,重复性和稳定性均符合标准要求,平均回收率在95%～105%之间,均符合标准GB/T 27404-2008《实验室质量控制规范食品理化检测》中的要求,且目标峰分离效果更好,效率提升49.5%。结论该方法的检测效率和分离效果较好,符合标准要求。     

福建省2003-2005年食品中空肠和结肠弯曲菌的监测与分析

目的系统分析福建省食品中空肠和结肠弯曲菌的污染现状、分布特征,建立和完善食源性致病菌监测网络,为制定相关的食品卫生干预措施提供可靠的基础数据。方法2003-2005年选择福建省的8个地级市和南北2个贫困县的农贸市场为监测点,采集生畜禽肉类、生牛奶、生食蔬菜、鸡蛋、水产品5大类共730份食品样品。按照WHO推荐并作为《全国食品污染物监测相关实验室操作手册(食源性致病菌部分)》的弯曲菌检验方法,用加有生长促进剂和特定配方抗生素的布氏肉汤增菌,将增菌液划线接种至弯曲菌选择性琼脂CCDA平板,挑取可疑菌落转种在哥伦比亚血琼脂平板上纯化。纯化的可疑菌落做革兰染色镜检,湿片观察动力,同时做过氧化氢酶试验、氧化酶试验、马尿酸盐水解试验、吲哚乙酸酯试验等生化鉴定。结果检出弯曲菌阳性的样品39件,总的阳性率为5·34%。分离到空肠和结肠弯曲菌47株,其中空肠弯曲菌34株、结肠弯曲菌13株。不同种类的食品阳性率不同,阳性率最高的为生肉6·72%(36/536),其次为生食蔬菜5·88%(2/34),水产品0·95%(1/105),生牛奶与鸡蛋中均未检出。生肉类中阳性率最高的为鸡肉7·31%(19/260)。结论福建省市售食品中存在着不同程度的弯曲菌污染,应加强食品中空肠和结肠弯曲菌的监测,加强禽畜养殖、屠宰、运输和加工过程的卫生管理,防止交叉污染,有效地预防和控制弯曲菌感染的暴发和流行。     

辅食营养补充品货架期内营养素的稳定性及叠加风险研究

本文主要对5种辅食营养补充品(1种辅食营养素撒剂和4种辅食营养补充食品)在货架期内营养素的稳定性及叠加风险进行了分析。稳定性试验结果表明,对于辅食营养素撒剂,维生素B₁的平均衰减率最高,为34.62%,其次是维生素D (30.77%)、B₁₂(30.14%)、B₆(29.41%)和A (29.10%),相对稳定的是钙(5.22%)。对于4种辅食营养补充食品,相对稳定的营养素均为蛋白质(0~0.93%)和钙(2.17%~11.30%),相对不稳定的营养素有维生素A (25.77%~30.74%)、D (22.37%~33.82%)、B₁(17.81%~25.93%)、B₂(25.00%~28.00%)、B₆(26.03%~33.33%)和B₁₂(13.11%~21.54%)。不同的品种其营养素的平均衰减率有一定的差异性。营养素叠加风险研究结果表明,婴幼儿在食用婴幼儿配方奶粉的同时摄入辅食营养补充品,需要根据食用的婴配粉营养素含量,科学选取适合的辅食营养补充品,以免产生某些营养素摄入过量风险。对于未食用婴幼儿配方奶粉的目标人群,同时选择婴幼儿米粉及辅食营养补充品食用则无摄入过量风险,反而对目标人群是一个很好的营养补充。     

Effect of frozen storage on the degree of vitamin B6degradation in different foods

Investigation of the effect of freezing and storage at-18° C for 5 months on the stability of total vitamin B₆ in foods of different origin leads to the conclusion that the decrease in vitamin B₆ content ranged from 18.92% to 60.26% and that the loss is significantly greater in food of animal origin (an average of 55.0%). Obviously, biostructure, that is chemical composition, is one of the basic factors affecting the degradation degree of vitamin B₆ in foods preserved by freezing. However, in relation of their biological value and with reference to the declaration allowing deep-frozen vegetables to be stored for 12–24 months, some foods of vegetable origin preserved by freezing exhibit a relatively high loss of biological value in terms of vitamin B₆ as early as after 5 months of storage.     

2000年～2003年广西细菌性食物中毒流行病学分析

为掌握广西细菌性食物中毒流行病学特点及其流行原因,为采取针对性防治对策提供科学依据,对2000年～2003年广西各地食物中毒报表与专题调查报告进行统计分析。2000年～2003年发生细菌性食物中毒105起,进食17915人,中毒3557人,中毒发病率19.85%,死亡34人,分别占同期广西各类食物中毒起数的22.83%,中毒人数的38.29%和死亡人数的27.64%;4～10月份是中毒高发月份;66.71%的中毒和100.00%的死亡人数集中在西北部的河池、百色以及中心城市南宁、柳州、桂林市;中毒原因主要是农村家庭聚餐、饮食服务单位、集体食堂制作的食物因原料(重点为肉类、谷类及制品)污染或加工不当、生熟交叉污染等所致;病原体构成第一位是沙门菌,其它依次为蜡样芽胞杆菌、金黄色葡萄球菌、变形杆菌、副溶血弧菌、椰毒假单胞菌、致病性大肠杆菌等;而进食人数发病率最高的是椰毒假单胞菌(98.61%),其次是沙门菌(38.58%)、金黄色葡萄球菌肠毒素(34.48%),最低的是由蜡样芽胞杆菌引起的食物中毒为10.65%;死亡病例全部系椰毒假单胞菌所产生的毒素污染酵米面所致。细菌性食物中毒是广西食物中毒的重要组成部分;不同食源性致病菌(毒素)引起的进食人员中毒发病率差异有显著性(P<0.01);广西西北部农村、饮食业和学校集体食堂等是细菌性食物中毒防制     

婴幼儿食品添加剂维生素B2的稳定性研究

目的研究婴幼儿配方粉中影响维生素B2稳定性的因素。方法本实验通过紫外可见光分光光度法,研究了光照、温度、p H、金属离子、氧化剂、抗氧化剂、防腐剂和糖类对维生素B2稳定性的影响。结果光照对维生素B2的影响最大,1 h损失率达到40%;金属离子中Mg2+5 h后会对B2造成约10%的损失;Fe3+和Cu2+可与维生素B2反应生成其他物质使B2造成破坏;维生素C在5 h后对维生素B2造成约13.8%的损失;常见的食品添加剂山梨酸钾和苯甲酸钠、以及氧化剂双氧水对维生素B2的影响有限;葡萄糖不能造成维生素B2的损失,蔗糖可以造成20%的损失。结论维生素B2的稳定性受多种因素的影响,其中影响最大的是光照,某些金属离子、维生素C和蔗糖也会影响维生素B2的稳定性。     

Retinol and beta carotene content of indigenous raw and home-prepared foods in Northeast Thailand

Retinol and β-carotene contents of raw and home-prepared indigenous foods in Northeast Thailand were studied. The criteria used to select the vitamin A-rich foods were high retinol or β-carotene contents of the individual food items, the amount and frequency of consumption, preference of consumption and food availability. Items selected were chicken liver, chicken egg, ivy gourd, amaranth, swamp cabbage (Chinese), Chinese cabbage, pumpkin, yellow sweet potato and two traditional menu items, kang-nho-mai and om-kruang-nai-kai. Raw food items were purchased from the local market; the traditional cooking procedures of the community were duplicated in the laboratory. Retinol and β-carotene contents were determined prior to and following cooking using HPLC methodology. The results indicated that boiling intact chicken liver resulted in 5% loss of retinol; boiling with cutting into small pieces and grilling resulted in losses of 8 and 16%, respectively. Greater losses (43%) were observed for egg omelet compared to hard-boiled egg (11%). For vegetables, blanching resulted in 7–11% loss of β-carotene, while steaming, frying and boiling showed losses of 15, 18 and 43%, respectively. Traditional foods such as bambooshoot soup (Kang-nho-mai) and chicken organ soup (Om-kruang-nai-kai) exhibited β-carotene losses ranging from 6–21%.     

Use of high performance liquid chromatography for analysis of vitamin A in food products

High-performance liquid chromatography (HPLC) was used for vitamin A assay in foods and raw materials. Metrological characteristics of this method have been estimated: relative standard deviation was 0.06-0.08, average recovery of vitamin A was 97.3 +/- 2.6 with n = 6, P = 0.95). The statistical analysis of the results obtained with HPLC has shown that it could be successfully used for vitamin A assay in varying foods containing no less than 0.01 mg of vitamin A per 100 g.