发酵方式及起始pH值对泡菜亚硝酸盐及硝酸盐含量的影响

以甘蓝为主要原料,采用自然发酵、陈泡菜卤水发酵、乳酸菌接种发酵以及调整起始腌渍液的pH值等发酵工艺,对泡菜腌渍过程中pH值变化、硝酸盐及亚硝酸盐的消长变化规律及影响因素进行了研究和分析.     

大白菜在贮存过程中亚硝酸盐含量的变化

在酸性条件下亚硝酸盐与对氨基苯磺酸重氮化后,再与盐酸萘乙二胺偶合形成颜色反应,建立了用比色法测定大白菜中亚硝酸盐的方法.观察大白菜在14d中亚硝酸盐含量的变化,得出随着贮存时间的延长,其中亚硝酸盐含量会逐渐升高,直到出现亚硝峰.在低温下放置时,到达一定时间,会进入食用安全期.     

百合泡菜的工业化发酵生产研究

利用乳酸菌与啤酒酵母双菌种混合发酵生产百合泡菜，采用正交试验，得到最佳的生产工艺条件为：乳酸菌与啤酒酵母比例为2：1，加糖量为5％，培养温度为28℃，培养时间为2d。产品色、香、味俱佳，酸甜可口，为工业化大生产提供了技术依据。     

NITRATE AND NITRITE CONTAMINATION IN VEGETABLES IN CHINA

This paper reviews recent studies of nitrate and nitrite contamination in Chinese vegetables. Nitrate and nitrite contamination is very serious and increases the amount of nitrogenous fertilizer applications. Factors influencing nitrate and nitrite contamination in vegetables are analyzed and discussed.     

NITRATE AND NITRITE CONTAMINATION IN VEGETABLES IN CHINA

This paper reviews recent studies of nitrate and nitrite contamination in Chinese vegetables. Nitrate and nitrite contamination is very serious and increases the amount of nitrogenous fertilizer applications. Factors influencing nitrate and nitrite contamination in vegetables are analyzed and discussed.     

EFFECT OF FERMENTATION ON THE FATTY ACID CONTENT AND COMPOSITION OF CASSAVA TUBER MEAL

The effect of fermentation on the fatty acids (FA) content and composition of cassava tuber meal has been investigated. The major FA of the cassava tuber meal (CTM) lipid were oleic and palmitic acids. Other FA found in decreasing order were linoleic, linolenic, palmitoleic, stearic, myristic, pentadecanoic, heptadecanoic and nonadecanoic acids. Fermentation of the CTM resulted in substantial increases in the absolute quantities of the individual FA detected except linolenic acid. However fermentation did not alter the pattern of composition of the FA, but it caused increases in the composition of saturated FA and decreases in certain unsaturated ones. Stearic acid increased in composition by about 92.6% and pentadecanoic by about 50%. A reduction of about 72% of the linolenic acid and 24.2% of the palmitoleic acid composition were obtained in the fermented CTM lipid.     

ORGANIC ACID AND SUGAR CONTENTS OF SCUPPERNONG GRAPES DURING RIPENING

Changes in the principal organic acids and sugars of Scuppernong grapes ( V. rotundifolia ) were followed during the ripening season. The vines were sampled bi-weekly during the initial stages of berry development and then weekly as harvest approached until the "overripe" stage was reached. At the ripe stage, malate and tartrate constituted approximately 90% of organic acids with trace quantities of pyruvic, fumaric, succinic, citric and quinic acids. Glucose, fructose and sucrose constituted approximately 90% of the sugars with trace quantities of galactose and maltose. Malate concentration increased during the early stages of ripening, peaked and decreased to a plateau at the ripe stage. Tartrate decreased steadily until it leveled at the ripe stage. Sugars began to accumulate at veraison, increased rapidly thereafter, and leveled at the ripe stage. At harvest, Scuppernong grapes contained 1.60% total acid and 9.45% total sugars on a whole berry basis. Individual constituents were 0.67% malate, 0.92% tartrate, 3.86% fructose, 3.98% glucose, and 1.61% sucrose.     

EFFECT OF LACTIC ACID FERMENTATION OF CASSAVA ON FUNCTIONAL AND SENSORY CHARACTERISTICS OF FUFU FLOUR

The effects of lactic acid fermentation of cassava on the functional and sensory characteristic of fufu flour were investigated. Two strains of Lactobacillus plantarum were used as starter cultures for the fermentation of cassava to fufu for 96   h. The resultant wet fufu samples were dried at 65C in a cabinet dryer for 48   h, and were analyzed for functional and sensory characteristics.
Fermentation reduced the water-binding capacity of the fufu flour from 176.6% to between 118 and 125%. The pasting characteristics of the traditional and starter culture-fermented fufu flour samples were not significantly different from that of the unfermented cassava flour. When subjected to sensory evaluation, the traditional and starter culture-fermented cassava fufu flour were not significantly different in terms of color, odor and texture, but the cassava fufu flour produced, using starter culture SL19, had the highest overall acceptability ( P <  0.05).

PRACTICAL APPLICATIONS

Traditionally, processing of cassava to fufu is usually carried out by using the old stock from a previous fermentation to initiate the fermentation of a new batch. This old method usually results in fufu that has a strong odor that may not be acceptable to some consumers. The use of starter culture like Lactobacillus plantarum will reduce the strong odor of fufu ; this will increase its acceptability by consumers and ensure the overall quality. Also, the functional properties of fufu are not affected. The development of lactobacilli strains could help in optimizing the traditional processes, therefore increasing the economic returns.     

离子色谱法测定火腿肠中的硝酸盐和亚硝酸盐

建立了离子色谱法测定火腿肠中的硝酸盐和亚硝酸盐含量的方法.利用纯水萃取火腿肠中的硝酸盐、亚硝酸盐,经过煮沸、冷冻、过滤后进样测定.经过多次实验,该方法样品加标回收率:硝酸盐99%～101%、亚硝酸盐96%～99%;标准曲线的相关系数分别为0.9990和0.9990.     

THE EFFECT OF ORGANIC ACID MARINATION ON TENDERNESS, COOKING LOSS AND BOUND WATER CONTENT OF BEEF

Longissimus muscle obtained from beef carcasses was used in this research. Initially, 0.596, 1.0% and 1.5% lactic and citric acid solutions were prepared. Meat was marinated in these solutions (1:4 w/v) in polyethylene bags at 4C for 72h. Bound water, pH, weight gain, cooking loss and Warner Bratzler shear (WBS) were evaluated. Differential Scanning Calorimetry (DSC) was used to determine the bound water content in meat samples. The latent heat of melting (ΔH_m) and bound water were found to be functions of moisture content of marinated meat. There was a significant decrease in pH due to marination. Compared to lactic acid, the samples marinated with citric acid held less water. The WS values in control samples were higher than in marinated samples. Cooking loss was lower in samples marinated with lactic acid compared to citric acid marinated samples.     

THE EFFECT OF PROCESSING ON THE TRYPSIN INHIBITOR, HEMAGGLUTININ, TANNIC ACID AND PHYTIC ACID CONTENTS OF SEEDS OF TEN COWPEA VARIETIES

Trypsin inhibitor (TI) and hemagglutinin activities, tannic acid and phytic acid contents were determined in ten varieties of cowpea. The different varieties were subjected to four processes; cooking, soaking, autoclaving and germination. TI and hemagglutinin activities were completely eliminated by cooking and autoclaving, while tannic acid and phytic acid contents were only partly affected. Cooking reduced tannic acid contents by 31.0–47.3%. Soaking for three days decreased TI activity by a mean of 31.2%, hemagglutinin activity by 19.0%, tannic acid by 13.4% and phytic acid by 24.4%. Maximum germination effects on TI and hemagglutinin activities were obtained in 'Westbreed' and 'Kano 1696' where percentage losses amounted to 57.2 and 57.6, respectively. The phytic acid contents of all varieties were greatly reduced by germination.