ANTIFUNGAL EFFECTS OF SORBIC ACID AND PROPIONIC ACID AT DIFFERENT pH AND NaCl CONDITIONS

The effect of pH (7, 5.6, 3.5), NaCl concentration (3 to 20% w/v) and EDTA on the antifungal activity of sorbic acid and propionic acid (Ca salt) against Candida spp. , Sporothrix sp. , Fusarium sp. , Penicillium spp. , Paecilomyces sp. and Aspergillus spp. was investigated by the Spiral Gradient End Point Test. Sorbic acid was active against most yeasts and molds, and in the presence of EDTA, which enhanced the effect of sorbic acid, all the organisms tested were inhibited. Sorbic acid was most effective at low pH. The inhibitory effect of sorbic acid increased with increasing NaCl concentration for all test organisms. Propionic acid was not as active as sorbic acid, but when combined with EDTA the inhibition was improved for some of the molds tested. Increasing or decreasing the pH did not change the antifungal activity of propionic acid. Synergistic effects of NaCl occurred at concentrations higher than 10%, but when EDTA was added, the inhibition was seen even at the lower NaCl concentrations.     

ENHANCEMENT OF ANTIMICROBIAL ACTIVITIES BY THE FOOD-GRADE MONOLAURIN MICROEMULSION SYSTEM

Monolaurin (M) is a potential natural antimicrobial agent used in foods. It is considered to have an antimicrobial activity against gram-positive bacteria. A monolaurin microemulsion (MME) system inhibited the growth of Bacillus subtilis, Escherichia coli, Aspergillus niger and Penicillium digitatum . Microemulsions (MEs) are transparent, isotropic solutions of oil, surfactant, cosurfactant and water, which are thermodynamically stable and have been much studied in terms of pharmaceutical and cosmetic applications. The growth of B. subtilis was inhibited more strongly by MME than by M. A similar pattern was observed for E. coli, A. niger and P. digitatum , although an enhanced inhibition by MME system over that obtained in comparable M alone was not observed.

PRACTICAL APPLICATIONS

Monolaurin is considered to have an antimicrobial activity against gram-positive bacteria but not against gram-negative bacteria. A monolaurin microemulsion system inhibited the growth of Bacillus subtilis , Escherichia coli , Aspergillus niger and Penicillium digitatum , and will be regarded as a "natural" antimicrobial preservative.     

INHIBITION OF ASPERGILLUS GROWTH AND EXTRACELLULAR AFLATOXIN ACCUMULATION BY SORBIC ACID AND DERIVATIVES OF FATTY ACIDS

A study was conducted to determine the effects of sorbic acid and several derivatives of fatty acids (amides, aminimides, and monoglycerides) upon toxigenic cultures of Aspergillus flavus and A. parasiticus. A synthetic medium was inoculated with spores, incubated for 48 h at 27°C, and then supplemented with sorbic acid and fatty acid derivatives. Cultures were then incubated for an additional 5 days. Aflatoxins were extracted, separated, and quantitated. Mycelial mats were dried, weighed, and analyzed for lipid and mineral content. Cerulenin (8 μg/ml) was the most effective fatty acid derivative examined, reducing mycelial growth by 37% and completely inhibiting extracellular accumulation of aflatoxins. Other derivatives, in decreasing order of effectiveness, included M-20 (an aminimide), lauribic, and lauricidin. Mycelia grown in the presence of fatty acid derivatives contained less phosphorus, potassium, magnesium, phosphatidyl ethanolamine, phosphatidyl serine, cholesterol, and triglycerides, but more cardiolipin, phosphatidyl choline, free fatty acids, fatty acid esters, and diglycerides. Levels of monoglycerides and cholesterol esters remained essentially unchanged. Inhibition by sorbic acid was nonspecific, affecting both mycelial growth and extracellular aflatoxin accumulation to approximately the same extent. Utilization of fatty acid derivatives for determining mechanisms of aflatoxin accumulation and lipid biosynthesis appears promising.     

DETERMINATION OF BENZOIC AND SORBIC ACID IN TURKISH FOOD USING HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY

Benzoic and sorbic acid levels in different brands of jam, candied chestnut, carbonated drink, pickle, black table olive, green table olive, wholemeal/brown bread and white bread, which are available on the Turkish market, were determined by high-performance liquid chromatography with diode array detector (235–254 nm). Chromatographic separation was achieved with a C18 column and acetate buffer (pH 4.74)–methanol mixture (70:30) as a mobile phase. The levels of benzoic and sorbic acid in the analyzed samples were in the range of not detected to 662 mg/kg or L, and not detected to 432 mg/kg or L, respectively. Only one sample (jam) presented a preservative although not permitted by the legislation enforced in Turkey. The levels of preservative in the other samples were determined in legal limitations. According to the results, the utilization of benzoic and sorbic acid is lower than the certain legal limitations permitted by legislation to be used.

PRACTICAL APPLICATIONS

The amount of the sorbic and benzoic acid used as preservatives during food processing is important for consumer health. Determination of the amounts of the preservatives mentioned above will be possible in a short period of time (11 min) with the methods used in this study (high-performance liquid chromatography). According to the results obtained from study and data about food consumption, daily intake amount of these preservatives (benzoic and sorbic acid) will be able to be defined in Turkey, separately.     

异Vc和Vc水溶液稳定性的比较研究

将Vc和异Vc配成水溶液，利用碘量法测定在不同时间、不同条件下它们的浓度，通过比较保存率，考察了水溶液pH值、金属离子和金属络合剂、光、水质、食盐和温度等因素对它们稳定性的影响。试验所表现出的总体规律是：相同条件下，Vc比异Vc更稳定。     

ANTIFUNGAL ACTIVITY OF MONOLAURIN AND RELATED COMPOUNDS

Lauricidin^R (monolaurin) and related compounds were tested against 16 fungi belonging to different groups and having different cell wall composition. Lauricidin Plus F (a combination of monolaurin, butylated hydroxy anisole and ethylenediaminetetraacetic acid) was the most effective agent and inhibited the growth of all fungi tested at a concentration of 0.1%. Lauribic (a combination of monolaurin and sorbic acid) also exhibited strong antifungal activity but was less effective than Lauricidin Plus F. In most cases Lauricidin showed antifungal activity at a concentration of 0.5%. Other commercial samples of monolaurin, e.g. Lauricidin 812 (A), Lauricidin 802 (B), and Lauricidin 112 (C), showed higher antifungal activity than Lauricidin. Tests comparing Lauricidin Plus F with sorbic acid, K sorbate and propionic acid, showed that Lauricidin Plus F has higher antifungal activity except when sclerotia of Sclerotium rolfsii were used for inoculation. Lauricidin Plus F was fungistatic and maintained its activity in a semi-synthetic medium for at least 21 days at 26°C.     

反相HPLC快速测定饮料中的苯甲酸和山梨酸

建立一种测定饮料中苯甲酸和山梨酸含量的快速反相高效液相色谱法。优化条件为：Lichrospher C18（250mm×4．6mm，5μm）反相柱，流动相为V（甲醇）：V（0．5g／L柠檬酸铵）=20：80，流速1．0mL／min，检测波长225rim。苯甲酸和山梨酸的直线回归方程分别为y=5171．56x-572．13和y=5089．85x-10．65，检测范围为0-90mg／L，相关系数为0．9999，回收率达98．3％-100．3％。分离时间从20min缩短至7min。     

COMPARISON OF THE FRYING STABILITY OF REGULAR AND LOW-LINOLENIC ACID SOYBEAN OILS

The frying stability of a regular soybean oil (RSO) was compared with a modified low linolenic-acid soybean oil (LLSO). The rate of free fatty acid (FFA) formation was similar for both oils during 72 h of frying. Despite a reduction in polyunsaturated fatty acids, however, the rate of formation of total polar compounds (TPC) in LLSO was greater than RSO. The higher production of TPCs in LLSO was explained, in part, by a lower level of tocopherols and a more rapid rate of degradation of the main isomers, γ- and δ tocopherols. This study points to the limitations of predicting frying stability based solely on fatty acid composition.