| Nipagin ester (also called as paraben or p-hydroxybenzoate), a wide-spectrum, high-effective and low-toxic food preservative, is recognized as one of the three main food preservatives internationally. Ethyl paraben, propyl paraben and butyl paraben has been domestically widely used as food preservative, whereas parabens with longer alcohol group represented as heptyl paraben has not been manuafactured and applied industrially. Heptyl paraben has the advantages such as low dosage, high effect and low toxicity when applied as preservative for alcoholic beverage. Mixed with the paraben with shorter alcohol group, heptyl paraben is more effective, more water-soluble, with its inhibitory spectrum widen. Heptyl paraben has a great application and development prospect; accordingly it is imperative for us to study the chemical synthesis technology, inhibitory characteristics and its preservative effect in specific food.In the first part, the synthesis of heptyl paraben was studied. The effect of reaction conditions i.e. different catalysts, the concentration of p-methyl phenylsulfonic acid as catalyst, temperature, the reaction time and the ratio of p-hydroxybenzoic acid and heptanol was studied, and it was shown that the better reaction conditions was: the concentration of p-methyl phenylsulfonic acid 3%, the ratio of acid and heptanol 3:1, temperature 180～185℃, time 5 hour. Furthermore, the esterification of heptyl paraben is further optimized by orthogonal experimental design, and it was shown after variance analysis that the ratio of p-hydroxybenzoic acid and heptanol affected the reaction foremost, reaction time the second, when heptyl paraben was synthesized with the optimized conditions the convertion rate of heptyl paraben reached 93.5%. The esterified product was ascertained as heptyl paraben after qualitative analysis with infrared spectroscopy, mass spectroscopy and HPLC. The synthesized heptyl paraben meet the requirement of the quality standards and can be applied in food when its content of heptyl paraben, acid degree, heavy metal, weight lost after drying, melting point and burning residue is assayed. And the recycling of heptanol and the feasibility of industrial manufacture is also discussed.In the second part, the inhibitory effect of heptyl paraben on common pollutant microorganism in food was studied. Heptyl paraben, a wide-spectrum high-effective food preservative, has evidently bacteriostatic action on common pollutant microorganism of food. The inhibition on gram-positive bacteria was the stronger, the inhibition on yeasts, molds and gram-negative bacteria the weaker. The minimal inhibition concentration (MIC) of this inhibitor on several bacteria, yeasts and molds was determined, its MIC on Staph. aureus, Bac. subtilis, Can. tropicalis and Asp. niger is respectively 12mg/L, 12mg/L, 24mg/L and above 24mg/L. The inhibitor remains good stability and inhibitory effect after heat treatment at 121℃ for 30min, and its inhibitory effect was not affected by high temperature when food is processed by heat, which benefited its application in food. Heptyl paraben was also stable to pH, and it remained strong inhibitory effect at the pH value that acidic food preservative became ineffective. Compared with that of ethyl paraben, propyl paraben and butyl paraben, the inhibitory effect of heptyl paraben was between that of ethyl paraben and propyl paraben, the inhibitory effect of butyl paraben was the greatest for its moderate solubility and absorption. As a result, heptyl paraben is suitable for preservation in alcoholic beverage.In the end, heptyl paraben was applied for preservation in sake and beer. Applied in unsterilized sake, heptyl paraben decelerated the growth of pollutant microorganism in sake. Applied in fresh beer initially, 12mg/L heptyl paraben kept beer fresh for a month without any sediment, which proved that heptyl paraben was a good beer preservative with a small deficiency of affecting the form and stability of foam. Heptyl paraben inhibited the growth of Lactobacillus sake and A...
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