黄瓜储存过程中硝酸盐和亚硝酸盐含量的动态变化研究

研究了黄瓜在不同储存温度(0~20℃)、储存方式(未包装,0.04 mm PE保鲜袋包装)条件下储存6 d期间,采用高效液相色谱法(HPLC)同时测定的硝酸盐和亚硝酸盐质量分数的动态变化情况。结果表明,在不同储存温度和储存方式下,硝酸盐和亚硝酸盐的质量分数随着储存时间的延长均呈现先增加、后降低的趋势。整个储存期间,硝酸盐与亚硝酸盐的质量分数均在安全食用范围内,即硝酸盐≤432 mg/kg;亚硝酸盐≤4 mg/kg。但在储存4 d后,黄瓜由于失水严重,感官品质严重下降,不建议食用。黄瓜中硝酸盐与亚硝酸盐的质量分数在储存过程中随储存温度的降低而显著减少,20℃和10℃储存黄瓜中硝酸盐最高质量分数分别是0℃储存的1.1和1.2倍,亚硝酸盐最高质量分数分别是0℃储存的2.7和2.9倍。PE保鲜袋包装有助于减少黄瓜在储存中硝酸盐与亚硝酸盐的质量分数。因此,建议储存黄瓜时最好采用PE保鲜袋包装,并尽快食用,以保证其食用安全品质。     

鲜姜、煮姜、泡姜中VC、硝酸盐、亚硝酸盐的含量测定

目的:测定姜经不同处理后VC、硝酸盐和亚硝酸盐的含量,以评价不同处理方法对营养成分VC和有害成分硝酸盐、亚硝酸盐的破坏情况。方法:通过紫外吸收分光光度计测得的特定波长下的吸收值来计算所测成分的含量。结果:生姜经煮沸15min后,VC的含量为2.30mg/100g,只有鲜姜中测得的VC的20.65%,而泡姜中VC的含量达5.86mg/100g,为鲜姜中的52.60%;鲜姜中硝酸盐和亚硝酸盐的含量分别为39338.5mg/100g和0.3046mg/100g,煮姜和泡姜中硝酸盐和亚硝酸盐的含量都很低。     

不同储存条件对芹菜和豇豆中硝酸盐和亚硝酸盐含量变化的影响

目的:研究不同储存时间、储存温度和包装方式对芹菜和豇豆中硝酸盐和亚硝酸盐含量的影响,为居民储存蔬菜提供科学依据。方法:在不同储存温度(4℃、25℃)、储存方式(敞口包装、密封包装)下储存芹菜和豇豆7d后,采用离子色谱法测定其中硝酸盐和亚硝酸盐的含量。结果:随着储存时间的延长,2种蔬菜中硝酸盐和亚硝酸盐含量会逐渐增加。低温4℃密封储存时硝酸盐、亚硝酸盐含量低,变化幅度最小。25℃密封储存时硝酸盐、亚硝酸盐含量高于25℃敞口储存时的含量。4℃敞口储存时硝酸盐、亚硝酸盐含量高于4℃密封储存时的含量。结论:应尽量食用新鲜蔬菜,如若储存应选择低温密封储存,有助于减少硝酸盐和亚硝酸盐的危害。     

大白菜贮藏过程中硝酸盐和亚硝酸盐含量变化分析

在不同贮藏温度（0、10、20 ℃）、贮藏方式（未包装、0.04 mm PE保鲜袋包装）条件下贮藏大白菜（Brassica rapa pekinensis）16 d后,采用高效液相色谱法测定大白菜中硝酸盐和亚硝酸盐含量的变化。结果表明,在不同贮藏温度和贮藏方式条件下,硝酸盐和亚硝酸盐的含量随着贮藏时间的延长均呈现先增加、后降
低、再上升的趋势,其中硝酸盐的含量在整个贮藏期间,均在低于432 mg/kg的安全食用范围内;亚硝酸盐含量在20 ℃贮藏条件下贮藏7 d即超过了4 mg/kg的安全摄入量,而其他贮藏条件均在安全食用范围内。大白菜中硝酸盐与亚硝酸盐的含量在贮藏过程中随贮藏温度的降低而显著减少,到贮藏末期（16 d时）20 ℃和10 ℃贮藏大白菜中硝酸盐含量分别是0 ℃贮藏的1.2 倍和1.1 倍,亚硝酸盐含量分别是0 ℃贮藏的1.4 倍和1.2 倍。PE保鲜袋包装有助于减少大白菜在中、低温（10、0 ℃）贮藏中硝酸盐与亚硝酸盐的含量,但在高温（20 ℃）贮藏中其含量增加。因此,建议贮藏大白菜时最好采用PE保鲜袋包装和0～10 ℃的贮藏温度,以保证其硝酸盐和亚硝酸盐含量不超标。     

冷藏对蔬菜中亚硝酸盐及硝酸盐含量的影响

目的 探索冰箱冷藏(4℃)条件下蔬菜中硝酸盐和亚硝酸盐含量随时间的变化,对冷藏食品的安全性进行评价.方法 分别采用重氮偶合分光光度法和麝香草酚分光光度法对生菜、菠菜、油麦菜及苦苣4种常用蔬菜在冷藏条件下其亚硝酸盐及硝酸盐的含量变化进行测定.结果 1～4d内,生菜、苦苣中的亚硝酸盐含量随着时间的延长逐渐增加;菠菜、油麦菜中亚硝酸盐含量分别在第2天和第3天达到最大,之后逐渐降低,而菠菜中亚硝酸盐含量在第4天又出现上升趋势.4种蔬菜中亚硝酸盐含量4d中最大值仅为0.419 4 mg/kg(生菜),均＜4 mg/kg的限量值.苦苣和油麦菜中硝酸盐含量在1～4d内逐渐上升.菠菜中硝酸盐含量第2天达到418.48 mg/kg,之后又降低至20.83 mg/kg.生菜中硝酸盐含量在第3天达到最大值317.26 mg/kg,之后逐渐下降,但均在安全范围内(432 mg/kg).结论 在4℃下冷藏4d后,4种常见蔬菜均可安全食用.可见,冷藏能有效减缓亚硝酸盐和硝酸盐含量的升高.     

亚硒酸钠对薇菜发酵中亚硝酸盐含量的影响

该试验研究了亚硒酸钠对薇菜发酵过程中亚硝酸盐含量的影响。分别添加亚硒酸钠于自然发酵和接种发酵的薇菜,发现亚硒酸钠可以降低“亚硝峰”;接种发酵薇菜,“亚硝峰”比自然发酵的低,且提前1 d出现,发酵8 d时,亚硝酸盐和硝酸盐含量皆比自然发酵的低。以接种发酵结束后的亚硝酸盐含量为评价指标,确定了发酵薇菜中亚硒酸钠的适宜添加量为0.3 g/L。通过添加Na2CO3维持发酵薇菜的pH值为5.0,发酵薇菜的“亚硝峰”提前1 d出现,且发酵结束时亚硝酸盐含量由自然pH时的2.16 mg/kg降为0。亚硒酸钠分3次添加,每次0.10 g/L时,“亚硝峰”提前至发酵3 d时出现,且添加次数增多时,发酵结束时亚硝酸盐含量也由一次性添加时的1.26 mg/kg降低到0.34 mg/kg,而硝酸盐也由0.13 g/kg降低到0.032 g/kg。     

鲜姜、煮姜、泡姜中Vc、硝酸盐、亚硝酸盐含量测定

测定姜经不同处理后Vc、硝酸盐和亚硝酸盐的含量，以评价不同处理方法对营养成分Vc和有害成分硝酸盐、亚硝酸盐的破坏情况。方法：通过紫外吸收分光光度计在特定波长下的吸收值来计算所测成分的舍量。结果：生姜经煮沸15min后，Vc的含量为2．30mg／100g，只有鲜姜中Vc的20．65％，而泡姜中Vc的含量达5．86mg／100g，为鲜姜中的52．60％：鲜姜中硝酸盐和亚硝酸盐的含量分别为39338．5mg／100g和0．3046mg／100g，煮姜和泡姜中硝酸盐和亚硝酸盐的含量都很低。     

几种食前处理对蔬菜中硝酸盐和亚硝酸盐的去除效果

过量摄取硝酸盐超标的蔬菜对人体健康危害严重。以武汉市售典型蔬菜为实验材料,参考国标法采用分光光度法研究浸泡、漂烫和去皮3种食前处理方法对硝酸盐和亚硝酸盐的去除效果。结果显示:采用食用白醋、果蔬洗涤剂或食盐水浸泡能不同程度降低蔬菜硝酸盐含量,其中对小白菜和菠菜的硝酸盐降低率最大可达32.5%和23.4%。叶类蔬菜经短时间漂烫可有效降低其硝酸盐含量,小白菜和菠菜用开水漂烫0.5min后,其硝酸盐含量分别降低了26.9%和14.5%。对根茎类和瓜果类蔬菜进行去皮处理亦可降低其硝酸盐含量或亚硝酸盐含量,白萝卜和黄瓜去皮后其硝酸盐含量分别降低6.5%和15.9%,茄子和白萝卜去皮后其亚硝酸盐含量分别降低12.2%和2.7%。可见,食前对蔬菜进行浸泡、漂烫和去皮的处理方式均能有效降低蔬菜硝酸盐或亚硝酸盐的含量。     

传统工艺山西老陈醋发酵及熏蒸过程中风味与功能成分的变化分析

探讨了山西老陈醋发酵及熏蒸过程中风味及功能性成分的含量及变化。结果表明,醋醅中酸、酯类含量较高,醛、酮和杂环类化合物的含量较低。熏蒸阶段,乙酸、庚酸含量增加,其他挥发酸的含量降低,醛、酮和杂环类的种类明显增加。多酚、黄酮的含量在酒精发酵阶段分别由1.42 g/100 g、17.10 mg/100 g增至2.07 g/100 g、34.48 mg/100 g,随后变化较小;游离阿魏酸的含量在酒精发酵第1～3天由9.34 μg/g降至0.59 μg/g,第4～16天基本不变,随后由19.49 μg/g增至66.54 μg/g。结合态阿魏酸的含量在酒精发酵阶段由634.75 μg/g降至421.42 μg/g,醋酸发酵前期增至1 607.5 μg/g,随后缓慢降低;川芎嗪在发酵的第22天开始检测到,第31天达到5.26 μg/g。γ-氨基丁酸含量在酒精发酵阶段由30.70 mg/100 g增至119.78 mg/100 g,随后其含量缓慢降至43.45 mg/100 g。     

我国进口干酪制品中硝酸盐、亚硝酸盐含量调查及暴露风险评估研究

目的 了解我国进口干酪制品中硝酸盐、亚硝酸盐含量水平,并评估我国成人干酪消费人群健康风险。方法 基于我国市售的进口干酪制品中硝酸盐、亚硝酸盐含量和2012年我国居民干酪消费量数据,通过概率评估方法,对我国成人干酪消费人群的膳食硝酸盐、亚硝酸盐暴露量进行估计,并分别与联合国粮农组织/世界卫生组织食品添加剂联合专家委员会（JECFA）制定的硝酸盐每日允许摄入量（ADI）和欧洲食品安全局（EFSA）制定的亚硝酸盐ADI比较后进行风险表征。结果 162份进口干酪样品中,硝酸盐的检出率为89.5%,平均含量为11.23 mg/kg;亚硝酸盐仅2份检出,含量为0.4和0.6 mg/kg。不同种类进口干酪制品中硝酸盐的平均含量从高到低依次为软质、半硬质、其他、硬质。我国成人通过进口干酪硝酸盐的平均暴露量为5.13 μg/kg BW/d,占ADI的0.14%,高暴露人群（P95）为20.06 μg/kg BW/d,占ADI的0.55%。结论 我国进口干酪制品中硝酸盐的检出率较高,且不同种类进口干酪制品其含量存在差异,而亚硝酸盐检出率很低。我国成人通过进口干酪暴露硝酸盐的健康风险较低。     

Nitrate and nitrite in vegetables from areas affected by war-time operations in Croatia

To evaluate nitrate and nitrite contents in cabbage and potatoes, the most consumed vegetables in Croatia, and to examine if war-time operations in Croatia affected nitrate and nitrite levels in vegetables, potatoes and cabbage cultivated in the war region (East Slavonia) and out of war regions were analyzed. Data showed that nitrate contents were higher in the samples from the war region (32% and 24% in potatoes and cabbage, respectively) but differences were not statistically significant. The nitrate levels found in potato samples (196 mg NaNO₃/kg fresh weight (FW) and cabbage samples (911 mg NaNO₃/kg FW) were comparable with levels reported for other countries. The nitrite contents in potatoes (321 μg NaNO₂/kg FW) and cabbage (173 μg NaNO₂/kg FW) were lower than the contents reported for most other countries. Further examinations of nitrate and nitrite concentrations in vegetables in Croatia as well as examinations of the influence of war-time operations on accumulation of these toxic contaminants are necessary.     

Nitrate and nitrite contents in vegetable juice, tea beverage and mineral water on the market

The contents of nitrate and nitrite in vegetable juice (n = 63), tea beverage (n = 12) and mineral water (n = 15) were measured. The mean contents of nitrate were 0.73 +/- 14.57 mg/100 g, 0.61 +/- 1.12 mg/100 g and 0.25 +/- 0.33 mg/100 g as NO3-, respectively. The contents of the nitrite were 0.03 +/- 0.05 mg/100 g, 0.02 +/- 0.01 mg/100 g and 0.001 +/- 0.001 mg/100 g as NO2-, respectively. The content of nitrate is high in some vegetable juices, and warnings may be necessary for people who drink them frequently.     

云南3种胶质食用菌营养成分分析与蛋白质营养价值评价

为了区别3种胶质食用菌在营养成分上的差异,为胶质食用菌的营养价值研究和深度开发利用提供一定依据,采用凯氏定氮法、索氏抽提法、原子吸收光谱法等方法对云南产3种胶质食用菌金耳、银耳、黑木耳的基本营养成分、矿物质、氨基酸的种类和含量进行测定,并通过氨基酸比值系数法对其蛋白质营养价值进行评价。结果表明:3种胶质食用菌的基本营养成分含量存在差异,以金耳的总糖含量最高,为75.30%,银耳的灰分含量最高,为6.40 g/100 g,黑木耳的粗蛋白、粗纤维含量最高,分别为11.20、9.70 g/100 g。3种胶质食用菌均含有人体必需的钙、钾、钠、镁、铁、锌等矿物质元素,但在含量上存在较大差异。以黑木耳的钙、镁、铁的含量最高,银耳的钾、钠、锌含量最高。3种胶质食用菌都含有17种氨基酸,其中包含人体必需氨基酸7种,谷氨酸和天门冬氨酸等鲜味氨基酸含量较高,必需氨基酸占总氨基酸的质量分数均高于FAO/WHO氨基酸模式谱,3种胶质食用菌SRC 值由高到低分别为银耳（82.25）>黑木耳（78.09）>金耳（77.98）,均在80左右,营养价值与利用率较高。3种胶质食用菌蛋白质营养价值差别不明显,都是含有较高蛋白质,低脂肪、高纤维、高总糖含量的菌类,具有较高营养价值和开发前景。     

Nitrate Analysis in Meats; Comparison of Two Methods

A high performance liquid chromatographic method (HPLC) was compared to cadmium reduction-Griess (Cd-Griess). Nitrate and nitrite were measured in fresh and cured meats. Nitrate levels by HPLC ranged from 6.2 to 26.7 nmol/g in fresh meats and from 124 to 3018 nmol/g in cured meats. Nitrate contents by HPLC were significantly higher (p<0.05) than those by Cd-Griess. Small amounts of nitrite (0–7.3 nmol/g) were detected in fresh meat samples by Cd-Griess. Results were similar to those used by the National Academy of Sciences to estimate human exposure to nitrate from fresh meats. Results from HPLC methods may provide more accurate estimates of human exposure to nitrate and nitrite.     

不同酿酒酵母对啤酒酿造过程中反-2-壬烯醛的影响

从不同生产用酵母菌泥中分离筛选出3株工业酿酒酵母,编号分别为A、B、C、D。以酿酒酵母C为对照,利用顶空固相微萃取结合气质联用（HS-SPME-GC/MS）法,研究不同酵母在啤酒酿造过程中反-2-壬烯醛（T2N）含量的变化。结果表明,不同发酵液中T2N含量差异显著（P＜0.05）,A、B、C、D酵母菌发酵液中T2N含量分别为13.63 μg/L、9.12 μg/L、10.93 μg/L、7.63 μg/L。4株菌的成品酒中T2N含量均较发酵液高,监测D菌啤酒酿造过程中T2N含量变化结果显示：冷麦汁中T2N含量最高为25.93 μg/L,发酵过程中T2N含量相对最低为6.96 μg/L,冷贮和成品阶段T2N含量有所增加,分别达到9.27 μg/L和11.36 μg/L,但与冷麦汁相比低很多。     

Nitrites, nitrates and N-nitrosoamines in Estonian cured meat products: Intake by Estonian children and adolescents

The contents of nitrate, nitrite and N-nitrosoamines in commercial cured meat products on the Estonian market were determined for 2000-01 and 2003-04 as part of the Estonian food safety monitoring programme and the Estonian Science Foundation grant research activities. The maximum permitted levels of residual nitrites and nitrates were not exceeded in the samples analysed. However, a great variation in the content of nitrate, nitrite and N-nitrosoamines was found for all the products. The concentrations of these compounds in domestic cured meat products showed a decrease from year to year. The mean intake of nitrate, nitrite and N-nitrosoamines by Estonian children (n = 346) from cured meat products was calculated on the basis of individual intake data. The mean daily intake of nitrates was 1.7 mg, that of nitrites was 0.83 mg and that of N-nitrosoamines was 0.073 µg. In the 2000-01 study, the calculated nitrite intake exceeded the acceptable daily intake by up to 140% for 1-6-year-old children and up to 105% in 2003-04.