芦荟汁对白菜发酵过程中亚硝酸盐及总酸含量的影响

本试验探讨了大白菜在无盐及有盐腌制发酵过程中,添加不同浓度的芦荟汁对亚硝酸盐含量变化的影响。结果发现,芦荟汁对无盐及有盐腌制发酵过程中NO2的形成有明显的抑制作用,添加物的浓度增大,抑制的效果增强。同时添加芦荟和Vc对抑制亚硝酸盐的生成有协同增效作用。通过测定发酵过程中总酸的变化,发现添加一定量的芦荟汁利于发酵作用的进行。     

重庆市蔬菜硝酸盐、亚硝酸盐含量及其与环境的关系

在重庆市的主要蔬菜中,硝酸盐含量依次为根菜类＞叶菜类＞葱蒜类＞瓜类＞豆类＞茄果类,前３类的硝酸盐含量超标,但各种蔬菜的亚硝酸盐含量一般较低,未超过卫生标准。就同一种蔬菜的不同样品而言,硝酸盐和亚硝酸盐含量的差异很大,说明品种或环境条件可显著影响其含量。重庆市多雾少光,冬春低温,土壤含氮量和钠高子含量较高,有效钾含量较低可能是导致蔬菜大量积累硝酸盐的环境因素。蔬菜不同器官硝酸盐和亚硝酸盐含量各异,根＞茎＞叶柄＞叶片。     

亚硝酸盐影响Lactobacillus brevis 4903发酵的研究

通过研究可知,亚硝酸盐对Lactobacillusbrevis4903发酵有抑制作用,环境中亚硝酸盐一旦分解掉,这种抑制作用就会被解除。分析其原因:①亚硝酸盐抑制了乳酸菌生长,从而抑制了乳酸发酵;②在发酵初期可能因亚硝酸盐还原酶的作用,使亚硝酸盐酶解生成NH3,NH3中和了乳酸菌生成的酸(H ),从而使环境pH值的下降和酸的积累变得缓慢。     

几种叶类蔬菜中硝酸盐和亚硝酸盐含量变化及其化学调控

几种叶类蔬菜中硝酸盐和亚硝酸盐含量变化及其化学调控陈振德,冯东升（青岛市农科所,青岛２３６１Ｕ０）（山东农业大学基础部,泰安２７１０１８）ＣＨＡＮＧＥＳＯＦＮＩＴＲＡＴＥＡＮＤＮＩＴＲＩＴＥＣＯＮＴＥＮＴＳＡＮＤＴＨＥＩＲＣＨＥＭＩＣＡＬＲＥＧＵＬＡ...     

家常菜和蔬菜中亚硝酸盐含量的变化

以6种家常菜和6种蔬菜为试验材料,研究在室温和低温（4℃）贮藏条件下以及炒制前后6种样品蔬菜中亚硝酸盐的变化情况。结果表明：在低温和室温条件下储藏12.5h,家常菜和蔬菜的亚硝酸盐含量不会超过4mg/kg的国家标准;叶菜类的亚硝酸盐含量高于根茎类;和室温相比,低温条件能够延迟叶菜的亚硝峰的到来,室温下叶菜的亚硝峰出现在7.5h,低温下叶菜的亚硝峰出现在10h,且亚硝酸盐的含量也少于常温。不同的蔬菜在炒制前后亚硝酸盐的变化不同。通过聚类分析,可以根据亚硝酸盐含量将24个试验样品分为两类。     

不同处理条件对叶菜类蔬菜亚硝酸盐含量的影响

目的：探明在采用盐酸萘乙二胺可见分光光度法下,测定具有代表性的叶菜类蔬菜中的亚硝酸盐含量在不同前处理条件下的变化。方法：采用常温（25±2℃）、冷藏（4℃）、密封冷藏（4℃）3种不同保存方式测定亚硝酸盐含量随着时间的变化规律;食前采用自来水、食用碱浸泡、果蔬洗涤剂浸泡及漂烫4种前处理方法。结果：3种不同保存方式下,随着时间的延长,亚硝酸盐含量表现为密封冷藏＜冷藏＜常温。自来水浸泡20min、5%食用碱浸泡、果蔬浸泡5min及漂烫0.5min 4种前处理方法均在一定程度上降低了蔬菜的亚硝酸盐的含量,且效果较其他清洗的处理条件稳定、明显,亚硝酸盐降低较快。结论：叶菜类蔬菜的亚硝酸盐含量在不同的放置条件下,均随存放时间的延长而增加。不同的食前处理均能降低亚硝酸盐含量,但在漂烫0.5min时,亚硝酸盐含量降低最为明显。建议消费者在选择叶菜类蔬菜时,冷藏储存,合理洗涤,避免长期放置。     

丙酸菌乳酸菌富硒发酵蔬菜的研制

目的 对丙酸菌乳酸菌富硒发酵蔬菜进行初步研制。方法 富硒丙酸菌、乳酸菌泡菜制作工艺流程：原料（洗涤整理）切分→盐水浸泡→装坛并放入辅料→加入老盐水（含乳酸菌）接种丙酸菌、Ｎａ２ＳｅＯ３１００μｇ／ｍｌ→培养。按泡菜、酸菜感官评分方法及评分标准,对不同处理的泡菜进行色、香、味、气、质地及滋味评分。并作产品无害化指标：Ｅ．Ｃｏｌｉ及亚硝酸盐浓度检测。采用３,３’－－二氨基联苯胺萃取分光光度法测定发酵蔬菜硒含量。蔬菜试样的试验指标有总硒质量分数「μｇ／ｇ」,有机硒质量分数「μｇ／ｇ」,以及有机硒占总硒的质量分数,分别代表该蔬菜对硒的吸收率变化及把无机硒转化成有机硒的转成率变化。结果 蔬菜虽未加硒作预泡处理,而是直接进行富硒发酵,泡制二天即可达到要求,随着泡制时间延长有机硒占总硒的质量分数有所下降,但下降幅度不如前者明     

不同轮作模式下土壤氮磷淋移和蔬菜硝酸盐、亚硝酸盐积累

2009年以沈阳市蔬菜生产示范基地为平台,研究不同轮作模式对消减设施菜地土壤氮、磷淋移和蔬菜硝酸盐、亚硝酸盐积累的作用.结果表明:经过一年的蔬菜种植后,设施菜地土壤pH呈下降趋势,下降了0.09～0.47单位;与本底相比,菜地土壤表层的全磷含量明显升高,速效磷含量(86.80～161.04 mg·kg-1)明显高于60 mg·kg-1的警戒指标,设施菜地土壤硝态氮(NO3--N)含量较高,并发生明显的淋移;除菠菜中亚硝酸盐含量超标外,3种轮作模式下的蔬菜硝酸盐和亚硝酸盐含量都符合国家无公害蔬菜安全标准;针对保护地土壤酸化、磷素累积和NO3--N淋移现状,应采取相应措施予以恢复;从3种轮作模式的结果看,在油菜一黄瓜-豇豆轮作模式下,土壤对pH的变化幅度最小,且土壤NO3--N的淋移现象较弱,氮、磷的回收率也较高,但在消减土壤磷淋移以及蔬菜硝酸盐和亚硝酸盐积累方面效果不明显.     

广东8种野菜中硝酸盐、亚硝酸盐及Vc的含量

测定了广东菊科8种野菜中硝酸盐、亚硝酸盐和维生素C的含量,结果表明：革命菜、一点红、苣荬菜的硝酸盐含量低于轻度污染水平,属于一级野菜;山莴苣、地胆草、加拿大蓬和艾的硝酸盐含量低于785mg/kg,达中度污染水平,属二级蔬菜范围,不宜生食,煮熟或盐渍可安全食用;甜菜籽属于三级蔬菜,不可生食和盐渍,可熟食.这些野菜维生素C的含量均低于50mg/100g（鲜重）,属于中、低维生素C含量的野菜.     

美味牛肝菌降低泡菜中亚硝酸盐含量的研究

亚硝酸盐是泡菜发酵过程中产生的一种有害的副产物。首次发现美味牛肝菌Boletus edulis子实体能显著降低泡菜中亚硝酸盐的含量。在实验组原料中加入新鲜美味牛肝菌子实体时,发酵第4天亚硝酸盐含量可降低97.1%。当泡菜中冷冻保藏的美味牛肝菌子实体的加入量分别为10%、20%、30%、40% 和50%时,发酵第4天对应的亚硝酸盐含量比不加美味牛肝菌的对照分别降低了20.9%、51.6%、93.9%、96.1% 和96.9%。发酵第6天开始亚硝酸盐含量降低百分比逐渐减小,发酵10d以上实验组和对照组中亚硝酸盐含量趋于一致,但此时的泡菜酸度增加、质量降低。此外,新鲜的和冷冻的美味牛肝菌子实体降低泡菜中亚硝酸盐的活性最高,常温晾干的活性次之,高温烘干的美味牛肝菌子实体没有降低亚硝酸盐的活性。     

Properties of nitrite reductase from Cucurbita pepo

Nitrite reductase purified to homogeneity from vegetable marrow contains 2 atoms Fe/mol. Enzyme-bound iron exchanged extremely slowly with ⁵⁹-Fe in solution. Acid-acetone extracts of the enzyme have a spectrum which is consistent with the presence of a sirohaem prosthetic group. Inhibition by mersalyl, which partially bleaches the enzyme, is reversible by glutathione only if this is added within a few min of mersalyl. The absorption spectra of the reduced and autoxidised enzyme and of the nitrite, cyanide and CO complexes are described. Amino acid composition data are given. The hydroxylamine reductase activity of the purified enzyme was 0.2% of nitrite reductase activity.     

泡菜中优良乳酸菌的分离、鉴定及发酵特性

从几种泡菜中分离出86株菌,对其在适温和低温下产酸速率及硝酸盐降解能力进行测定,筛选出5株产酸速率快、硝酸盐降解能力强的菌株。经形态学鉴定及生理生化反应试验,初步鉴定为：植物乳杆菌2株,短乳杆菌1株,戊糖乳杆菌1株,肠膜明串珠菌葡聚糖亚种1株,并对5株菌的发酵性能进行了测定。     

Nitrite,hydroxylamine and sulphite reductases in wheat leaves

The inclusion of cysteine and Na-EDTA in the extracting buffer lowered the activity of sulphite reductase extracted from wheat leaves while nitrite and hydroxylamine reductases were not so affected. Maximum activity for the three enzymes was achieved with reduced methyl viologen as the electron donor. The three enzyme activities were found in the chloroplasts. Nitrite reductase was detected in the leaves of the seedlings only when grown with nitrate and exposed to light. Sulphite and hydroxylamine reductases were not, however, influenced by either of these treatments. These results suggest that nitrite reductase is a distinct enzyme and is not associated with sulphite reductase and hydroxylamine reductase in wheat leaves.     

Vegetable oils in fermentation: beneficial effects of low-level supplementation

To evaluate their potential to enhance fermentation performance, vegetable oils were investigated in a model tetracycline fermentation. With sucrose as the carbon source, the fermentation efficiency of Streptomyces aureofaciens (ATCC 10762) was enhanced by the inclusion in the medium of low levels of vegetable oil. Soybean and sunflower oils significantly improved the rate of sucrose consumption and tetracycline production suggesting that oil is an excellent adjuvant for improving fermentation productivity. For optimum benefit, the dosage level was critical. Little difference was observed between crude and refined oils. These data contribute to the assessment of industrially available fermentation feedstocks, and to the development of new feedstock products for specific fermentation applications. Received 24 February 1998/ Accepted in revised form 8 September 1998