Suspected mode of antimycotic action of brevicin SG1 against Candida albicans and Penicillium citrinum

Brevicin SG1, a novel, broad spectrum bacteriocin produced by Lactobacillus brevis SG1 isolated from ‘ogi’, a traditional Nigerian fermented cereal, was studied for its effects on fungal hyphal growth and morphology. The bacteriocin caused some morphological changes and a decrease in the total mass of Candida albicans and, cellular damage and an inhibition of pre-formed germ tubes in Penicillium citrinum. The inhibitory action was concentration- dependent, confirming that antibiosis was the mode of antagonism.Transmission scanning electron microscopy (TSEM) study revealed that the bacteriocin caused hyphal destruction and lysing of the cell wall in P. citrinum and distortion of shape in C. albicans. TSEM result suggested that the fungal cell wall and the cell membrane were the main target of this antifungal compound and the suspected mode of action was fungiolytic. Disintegration of fungal hyphae was probably due to a membrane disorder causing increased membrane permeability and the consequent osmotic effect.The bacteriocin was stable over a wide range of pH (1–10) especially between pH 5–7 while its production was maximal at pH 6.5. The production and stability of the bacteriocin at a broad pH makes it a suitable agent for controlling spoilage organisms of most foods and for using it as starter cultures of fermented foods. It also has the potential for probiotic usage.     

Effect of sodium alginate-based edible coating containing different anti-oxidants on quality and shelf life of refrigerated bream (Megalobrama amblycephala)

The effect of alginate-based edible coating containing Vitamin C (Vc) and tea polyphenols (TP) for shelf-life extension of bream (Megalobrama amblycephala) was evaluated over a 21-day storage at refrigerated temperature (4 ± 1 °C). Bream were left untreated (CK), or were treated with alginate–calcium coating (T1), alginate–calcium coating incorporating 5% Vc (T2), or alginate–calcium coating incorporating 0.3% TP (T3). The fish samples were analyzed periodically for water loss, microbiological (total viable count), chemical (pH, total volatile basic nitrogen (TVB-N), thiobarbituric acid (TBA), K-value) and sensory characteristics. The results indicated that coating treatments retarded the decay of fish compared to uncoated bream. T2 more efficiently inhibited the growth of total viable counts than did T1 or T3 (p < 0.05). Coating treatments predominantly reduced chemical spoilage, reflected in TVB-N, pH, and TBA, retarded water loss (p < 0.05) and increased the overall sensory quality of fish compared to uncoated bream.     

The changes in black tea quality due to variations of plucking standard and fermentation time

Catechin levels in green leaf, total theaflavins, brightness, thearubigins, colour, flavour index and sensory evaluation decrease with coarse plucking standard in clone 6/8. The sum of Group I volatile flavour compounds and C₆ aldehydes and alcohols, in particular, increases with coarse plucking standard. The sum of Group II did not follow a particular pattern, but flavour index decreased with coarse plucking standards. The decrease in total theaflavin levels was due to the decrease in all the individual theaflavins. Although all the individual theaflavin levels decreased with coarse plucking standards, the decrease was greater in galloylated theaflavins, especially in theaflavin digallate, compared with simple theaflavin. Short fermentation times produced black teas with higher brightness and flavour index, but lower theaflavins, thearubigins and colour, irrespective of plucking standard. Total theaflavins reached a maximum after 90 min of fermentation, irrespective of the plucking standard, whereas ungalloylated theaflavin levels decreased with extended fermentation duration at all plucking standards, theaflavin-3-gallate and theaflavin-3, 3’-digallate levels increased, resulting in the increase in theaflavin digallate equivalent. Brightness and flavour index decreased while thearubigins, colour, and Groups I and II volatile flavour compound levels increased with long fermentation.     

The impact of processing techniques on tea volatiles

The impact of various cultural and manufacturing techniques on volatile flavour composition was studied in order to optimize the conditions for production and retention of aroma in relation to tea quality. The Flavour Index was in the order: clonal variation—Assam > > Cambod > China Shoot maturity—Bud + 1st leaf > > > 2nd leaf > > 3rd leaf; plucking interval 7 day > 14 day; processing—green leaf > withered leaf—fermented dhool < dried tea < < tea brew; withering—soft < normal < hard. VFC Group I was in general dominated by trans-2-hexenal and Group II by linalool, phenylacetaldehyde and geraniol. Fresh green leaf had a high content of hexanol, hexanal, hexenol, hexenal and methyl salicylate. Upon withering, a sharp increase in Group I was noticed, the most remarkable being in hexenol. Group II also increased, but the extent was less except for linalool. During fermentation, Group I alcohols showed a sharp reduction with concomitant increases in aldehydes, especially trans-2-hexenal. In Group II, all compounds increased except methyl salicylate and the ionones. In the firing stage, high losses of Group I and Group II were registered. All the Group I compounds showed a decline with the progress of withering, but the opposite applied to Group II compounds, except for the alcohols. Mechanical injury during handling of leaf before cutting increased the Group I content enormously. The addition of exogenous fatty acids, mainly linoleic acid, produced substantial amounts of Group I compounds, dominated by trans-2-hexenal and hexanal. The inhibition of lipoxygenase totally reduced the formation of Group I volatiles.     

符离集烧鸡加工过程中的营养和理化品质变化

通过对符离集烧鸡在5个不同加工阶段下主要成分、pH、嫩度、食盐、总糖、氨基酸含量等的测定,探究其在加工过程中营养和理化品质的变化。结果表明,在加工过程中,鸡胸肉和鸡腿肉的水分含量、剪切力显著下降(P<0.05),灰分、蛋白质、脂肪以及食盐含量显著增加(P<0.05);卤制后鸡胸肉(pH=6.45)和鸡腿肉(pH=6.65)的pH达到最大,杀菌后有所下降;油炸时鸡胸肉和鸡腿肉总糖含量分别增加了75.34%和72.62%(P<0.05),卤制和杀菌后鸡肉的总糖含量下降。烧鸡加工过程中共检出17种氨基酸,其中谷氨酸(16.31%~17.11%)、天冬氨酸(9.53%~10.42%)、亮氨酸(8.16%~8.53%)、赖氨酸(8.48%~9.10%)是烧鸡中最主要的氨基酸,谷氨酸的含量最高。除苯丙氨酸外,成品烧鸡中必需氨基酸均高于FAO/WHO/UNU推荐含量,可见烧鸡具有较高的营养价值。卤制对烧鸡其营养品质影响较大,杀菌保证了产品安全性的同时,对其营养及理化品质无不良影响。     

Effects of storage period and temperature on the technological properties,starch digestibility,and phenolic compounds of mung beans (Vigna radiata L.)

This study aimed to evaluate the effects of storage period (0, 2, 4, and 6 months) and temperature (15 °C, 25 °C, and 35 °C) on the germination, vigor, technological properties, starch digestion, and phenolic compound content of mung beans. The germination, vigor, protein solubility, inhibition of the ABTS radicals, and the total free and bound phenolic compound content reduced while cooking time, leached solids, and electrical conductivity increased during storage. Minor changes were observed in grains stored at 15 °C. Starch digestion was higher in stored grains than in freshly harvested beans; however, it decreased on increasing the temperature. The content of bound gallic acid, bound chlorogenic acid, free and bound ferulic acid, free and bound rutin, and free and bound quercetin contents reduced after storage. In contrast, the content of bound caffeic acid, bound vanillic acid, bound myricetin, free coumaric acid, and free catechin contents increased after storage at 15 °C. These results suggested that mung beans could be cooled at 15 °C to reduce the detrimental effects of storage and maintain the nutritional value and germination viability.     

Comparison of chemical compositions of Ilex latifolia Thumb and Camellia sinensis L.

Chemical composition of two beverage plant species, i.e. Ilex latifolia and Camellia sinensis were investigated. Fifteen and sixteen amino acids were detected in I. latifiolia and C. sinensis, respectively. Major amino acids were histidine, aspartic acid and glutamic acid in I. latifolia but theanine, glutamic acid and histidin in C. sinensis. Ascorbic acid and polyphenols in I. latifiolia were 0.46 mg g⁻¹ and 90.1 mg g⁻¹, less than one fourth and one half of those in C. sinensis, respectively. Eight catechin compounds were found in C. sinensis but only four in I. latifolia, i.e. l-catechin (C), l-epicatechin (EC), l-epicatechin gallate (ECG) and l-catechin gallate (CG). Three flavonoids, i.e. rutin, mericetin and quercetin were detected and their total contents in I. latifolia and C. sinensis were 4781 mg kg⁻¹ and 580 mg kg⁻¹, respectively. Caffeine was not detected in I. latifolia. The higher concentration of flavonoids in leaf of I. latifolia may be related to its value for a healthy beverage.     

Mechanism of Phospholipid Hydrolysis for Oyster <Emphasis Type="Italic">Crassostrea plicatula</Emphasis> Phospholipids During Storage Using Shotgun Lipidomics

A fast and efficient shotgun lipidomics strategy was applied to analyze phospholipids (PL) in the oyster Crassostrea plicatula, including 29 species of phosphatidylcholine (PtdCho), 23 species of phosphatidylethanolamine (PtdEtn), 11 species of phosphatidylserine (PtdSer), 6 species of phosphatidylinositol (PtdIns), and 17 species of lysophospholipids (Lyso-PL). During storage at 4 °C for 7 days, the PL content decreased by 68.08%, but a significant increase in the FFA content was observed (from 63.11 to 318.72 μg/g). PtdCho and PtdIns decreased relatively by 64.97 and 67.49%, and PtdSer decreased most markedly by 74.15%. However, the PtdEtn content increased slightly during the early stages of storage but subsequently began to decrease. Moreover, PL with eicosapentaenoic acid (EPA-PL) and docosahexaenoic acid (DHA-PL) decreased by 51.77 and 50.61%, whereas plasmalogens were relatively stable showing only a 25.46% decrease. In particular, through enzyme activity analysis of lipase, phospholipase A₁ (PLA₁), phospholipase A₂ (PLA₂), phospholipase C (PLC), and phospholipase D (PLD), it was observed that the activities of all these enzymes increased at the early stage at 4 °C, but their activities were at lower levels when the oysters were stored at ?20 °C. During the storage period at 4 °C, correlation analysis suggests that the degradation of PtdCho was mostly correlated to PLA₂ (p < 0.05), whereas PtdEtn and PtdSer were more markedly correlated to lipase and PLD, respectively. The above result indicates that the hydrolysis mechanism of PL during seafood storage was correlated to the lipid hydrolytic enzyme activities under different storage temperatures.     

橄榄多酚氧化酶和过氧化物酶的抑制剂筛选及其热失活动力学

本项目研究了七种抑制剂(分别为亚硫酸钠、明矾、O-异抗坏血酸、EDTA-2Na、Ca Cl2、多聚磷酸钠、柠檬酸亚锡二钠)对橄榄多酚氧化酶和过氧化物酶活力的影响,并采用两段模型分析了高温处理对橄榄果实多酚氧化酶(PPO)和过氧化物酶(POD)的钝化动力学。结果表明,橄榄中酚类化合物氧化分解与POD和PPO活性有关,在特定的环境条件下,O-异抗坏血酸和柠檬酸亚锡二钠抑制橄榄PPO酶和POD酶活性效果最好,譬如,其浓度为0.20 g/L时,可完全抑制橄榄PPO酶和POD酶活力;热烫时间和温度对橄榄果实PPO和POD活性影响较大,并随着热烫时间和热烫温度的增加,橄榄果实PPO和POD活性呈现先下降后处于平稳的趋势,故高温处理对橄榄PPO和POD的钝化过程符合两段模型。