Study Of The Antibacterial Activity Of Purple Sweet Potato Anthocyanins Compound With Preservatives Optimized By Response Surface Methodology

Purple sweet potato anthocyanins (PSPAs) are not only a natural pigment but also had antibacterial effect. At present there are lots of research reports about the method of extracting and purifying PSPAs. In recent years, with the improvement of people’s living standard and health consciousness, people’s demand for safe food is increasing constantly. The dosage of chemical preservatives is wanted to be reduced in food. Studies show that when several natural preservatives compounded or one natural preservative compounded with other chemical preservatives, the compounds could give better antibacterial effects than it is used alone because of synergy effect, the advantages of this are that it not only could obtain better antibacterial effect with less dosage of preservatives, but it also could moderate the conditions of sterilization and bacteriostasis of food. Because most of the natural active substances have pHysiological activity, so they have good healthcare function to human health.In this article, the optimum conditions of ultrasonic wave-assisted extraction technology for PSPAs are determined with the Response Surface Methodology (RSM) based on single factor analysis, AB-8macroporous resin and thin layer chromatograpHy (TLC) are used to purify PSPAs, which not only could shorten the extracting times but also could increase the extracting rate, The effect of pH、 temperature and ultraviolet rays to PSPAs bacteriostatic actions are also studied for the first time in this article.The focus of this article is the innovative use anthocyanins which have been extracted and purified as natural antibacterial substance compounded with food preservatives potassium sorbate and sodium benzoate, optimize the best proportions of three factors compound by an innovative use of the RSM, and then study the bacteriostatic action of StapHylococcus aureus、Escherichia coli、Bacillus stubtilis、White mold and Monilia albican through bacteriostasis experiments, select the best antibacterial compound to each strain, and design experiment on the simple application in steamed bread、fresh pork and pineapple juice drinks. The relevant conclusions are as follows:(1) The optimum conditions of ultrasonic wave-assisted extraction technology for PSPAs are:the best extraction solvent for PSPAs is acidulated alcohol [1.5mol/L HC1:95%ethanols (v/v)=15:85]. The best extraction conditions of PSPAs which are determined by RSM are:ultrasonic time,16min; extracting time,70℃; liquid ratio, 10. Under these conditions, the actual production of anthocyanins is363.24mg/100g. The color value of PSPAs which have been purified is20.4.(2) The result of the research for the first time of the effect of pH、temperature and ultraviolet rays to PSPAs bacteriostatic action are:PSPAs have the best bacteriostatic action under acid condition; the bacteriostatic action of PSPAs is almost unaffected under high temperature-short time, but have a certain decrease under high temperature for a long time, and almost unaffected under the instantaneous high-temperature; At the same time, the bacteriostatic action of PSPAs is almost unaffected by UV treatment.(3) This article first use PSPAs as natural antimicrobial substances compound with sodium benzoate and potassium sorbate to do bacteriostasis experiments, the relevant conclusions are as follows:a:The MIC of optimal compound of sodium benzoate-potassium sorbate or sodium benzoate-potassium sorbate-PSPAs are lower than single factor through comparison, which indicate that the synergy effect between compounds could improve bacteriostatic efficacy.b:The optimal proportion of the bacteriostatic compound for each strain are: StapHylococus aureus:sodium benzoate:potassium sorbate:PSPAs=0.480:0.260:2.05; Escherichia coli:sodium benzoate:potassium sorbate:PSPAS=0.550:0.290:6.59; Bacillus stubtilis:sodium benzoate:potassium sorbate=6:4; White mold:sodium benzoate:potassium sorbate:PSPAs=0.300:0.290:13.9; Monilia albican:sodium benzoate:PSPAs=7:3.c:The interactions between PSPAs and other two preservatives are different to different kinds of bacteria, and the antibacterial effect is also different to different kinds of bacteria. To StapHylococcus aureus, Escherichia coli and White mold, the optimal compounds are the mixture of sodium benzoate-potassium sorbate-PSPAs, when add PSPAs, the MIC of the compound of sodium benzoate-potassium sorbate-PSPAs are lower than the compound of sodium benzoate-potassium sorbate, and also lower than single factor, which indicate that PSPAs are not only have significant effect between sodium benzoate and potassium sorbate, but also could improve the bacteriostatic effect. But to StapHylococcus aureus, the optimal compound is sodium benzoate:potassium sorbate=6:4, which indicate that PSPAs have not significant effect when compound with other two preservatives, while to Monilia albican, the optimal compound is sodium benzoate:PSPAs=7:3, which indicate that interaction between PSPAs and sodium benzoate is significant than the compound of sodium benzoate-potassium sorbate and the compound of sodium benzoate-potassium sorbate-PSPAs.(4) Add the optimal compounds to steamed bread、fresh pork and pineapple juice drinks to design simple fresh-keeping experiment, the results prove that the fresh-keeping effect of experimental group of adding preservatives are better than the controls, and fresh-keeping effect of the optimal compounds are better than the compound of sodium benzoate-potassium sorbate, which indicate that bacteriostasis function of the optimal compound are the best and could prolong the quality guarantee period of food.