The effect of nisin and garlic (Allium sativum L.) essential oil separately and in combination on the growth of Listeria monocytogenes

In the present study, the anti-listerial activity of the nisin and garlic (Allium sativum L.) essential oils (GO) alone and in combination was investigated at different temperatures (20 and 30 °C), pH (6.8, 5.6 and 4.8) and NaCl concentrations (0, 0.5, 2.5 and 4.5 g/100 mL). Minimum inhibitory concentrations (MICs) against Listeria monocytogenes were assessed for the nisin and essential oil. Furthermore, for combinations of the antimicrobials, the Differences in Population (DP) method were used to determine their effect. Both essential oil and nisin possessed considerable antimicrobial effects on the microorganism. The MICs for nisin and GO were 12.5 IU/mL and 100 μg/mL, respectively. Regardless of NaCl concentration and temperature, the anti-listerial activity of both GO and nisin was strongly influenced by pH. Moreover, at the same temperature, and regardless of pH value, the growth of the organism was also affected by increasing NaCl concentration. In combination, the DP was related strongly to the agent’s concentration and media pH. Meanwhile, among all combined systems, the effect of the combination (EC) of nisin with GO at 30 °C, pH 5.6 and 0 g/100 mL NaCl, showed significant anti-listerial activity (P ≤ 0.05).     

大蒜渣中混合氨基酸的提取工艺研究

通过水解法,活性炭吸附,丙酮降解对氨基酸的提取,首次确定了从大蒜渣中提取混合氨基酸的最佳工艺条件为:盐酸浓度25%,温度107℃,水解时间8h提取效果最佳;活性炭为投入渣量的12%,在75～80℃脱色25min效果最好;当pH为3.0、乙醇用量是水解液体积的1.25倍,混合氨基酸的产率可达6.5%.     

防止蒜泥绿变方法的研究

研究了不同的处理方法对蒜泥绿变的影响。并通过效果比较,确定了两种防止蒜泥绿变的较好方法。     

硅窗袋贮藏蒜苔的技术研究

采用带硅橡胶薄膜的低压聚乙烯塑料袋贮藏蒜苔,控制0~－0．5℃的稳定库温;90%~95%的相对湿度;气体成分为O_21．0%~2．0%,CO_2 5．0%~7．0%。可以收到比普通塑料袋气凋好的效果,贮期7个月以上,总损耗率＜1．0%,保鲜指数98．5%,商品率＞99．5%。     

Dehydration of Garlic Slices by Combined Microwave-Vacuum and Air Drying

Combination of microwave-vacuum drying and air drying was investigated as a potential mean for drying garlic slices. The sample was dried by microwave-vacuum until the moisture content reached 10% (wet basis), and then by conventional hot-air drying at the temperature of 45°C to final moisture content less than 5% (wet basis). Pungency, color, texture, and rehydration ratio of garlic slices dried by this method were evaluated and compared with those dried by freeze drying and conventional hot-air drying. The comparison showed that the quality of garlic slices dried by the current method was close to that of freeze dried garlic slices and much better than that of conventional hot-air dried ones. The lab microwave-vacuum dryer which the materials to be dried could be rotated in the cavity was developed by the authors.     

Stabilization of sunflower oil by garlic extract during accelerated storage

Efficacy of garlic extract in stabilizing sunflower oil during accelerated storage has been studied. Extracts of garlic were prepared in different solvents; extract yield was in the range of 6.24–23.2% and antioxidant activity range in the linoleic acid system was 14.1–93.2%. Being highest in yield and antioxidant potential, methanolic extract was thermally evaluated by heating the extract at 185 °C for different intervals, i.e. 0–80 min and evaluating antioxidant activity of the heated extract in the linoleic acid system (71.6% inhibition). Methanolic extract of garlic at three different concentrations, i.e. 250 (SFO-250), 500 (SFO-500) and 1000 ppm (SFO-1000) were added to preheated RBD sunflower oil. BHA (SFO-BHA) and BHT (SFO-BHT) at 200 ppm served as standards besides the control. Weight gain (WG), antioxidant activity index (AAI), free fatty acid (FFA) content, peroxide value (PV), conjugated dienes (CD), conjugated trienes (CT) and thiobarbituric acid-reactive substances (TBARS) were taken as parameters for evaluation of effectiveness of garlic in stabilization of sunflower oil. Results from different parameters were in agreement with each other, suggesting the highest efficiency of SFO-1000, followed by SFO-BHT, SFO-BHA, SFO-500, SFO-250 and Ctrl. Results reveal garlic to be a potent antioxidant for stabilization of sunflower oil.     

Biochemical studies with garlic (Allium sativum) cell cultures showing different flavour levels

Garlic (Allium sativum L) cell cultures, unorganised white as well as organised green callus, revealed a total of five amino acid precursors (methyl, propyl, allyl, cysteine sulphoxides) and two unidentified ninhydrin-positive compounds. All the five compounds were hydrolysable by alliin lyase to yield pyruvic acid. Their relative concentration varied in the cultured systems and the explant. The total flavour substrate index in globular white callus and semi-differentiated green callus was 4 and 13% respectively of the original explant. In contrast to the substrate levels, the specific activity of alliin lyase enzyme showed half the original activity of the garlic bulb explant. The relationship between intermediary metabolism and flavour formation was studied in these cultures with the help of ¹⁴C-glucose and ¹⁴C-methionine. The incorporation of ¹⁴C label was lower in the protein, carbohydrate and lipid fractions with a concomitant higher incorporation in the volatile fraction of semi-differentiated cultures, whereas this trend was reversed in the white globular callus. ¹⁴C Conversion to the flavour fraction was much lower in the in-vitro cultures when compared with the garlic bulb. The activity of some enzymes such as amino transferase, malate dehydrogenase, polyphenol oxidase, peroxidase, and alkaline phosphatase was higher in the cultured cells than in garlic bulb. There were differences also in the protein, free amino acid profiles and peroxidase isozymes of garlic cell cultures and the original explant.     

大蒜病毒原与其寄主细胞病理变化的电镜研究

电镜检查发现田间4个品种栽培大蒜各部位组织都含大量线形病毒粒子,长度为300nm～2200nm,但较多的集中在750nm和600nm两个范围内。感病大蒜叶组织细胞质大量存在着圆柱状内含体,内含体显然与内质网、质膜和胞间连丝有关。病毒粒子散布在细胞质中,有些附着在内含体上,未见病毒聚集体。病变细胞严重空泡化,有些细胞质中出现大量含纤维状物的小囊泡和类似内质网膨大的结构,同时伴随着大量病毒粒子。叶绿体和根细胞中的前质体产生特殊泡状腔结构,细胞核中未见内含体和病毒粒子。     

辐照大蒜生长点细胞超微结构及抑制发芽效果的研究

电镜观察表明：受０．０２、０．０５或０．３ｋＧｙγ射线辐照大蒜的生长点细胞的超微结构受到不同程度的损伤，生长点细胞变长，细胞壁增厚。，微结构中液胞对辐照敏感性最强，核仁和线粒体最抗辐照，在细胞壁受损破裂情况下，仍保持基本完，萌动期的结构损伤较休眠期显著，说明通过代谢活动，使辐照损伤进一步扩大，因此细胞分裂受阻，抑制大蒜的发芽。