Study On Ozone Combined With Superheated Steam On Sterilization Of The Dried Garlic Slices

Garlic(Allium sativum L)is one of the most important vegetables in China,which has important edible and medical value.It was difficult to kill the microorganisms during hot-air drying of these products.In this research,we used ozone,superheated steam and ozone combined with superheated steam to process dehydrated garlic slices,so as to reduce the number of microorganisms and reach the exportation standard.All the results can also provide guidance for manufacture garlic products in an industrial scale.The results are shown as follows:1.150 g of dehydrated garlic slices,the water content of which was 5.61 ± 0.06%,was put in a closed chamber.The thickness of the monolayer garlic is 3 mm.The effect of ozone concentration and treating time on the total number of bacteria and the quality of dehydrated garlic slices at 25 ? and RH 60%was investigated.The results showed that the total number of colonies in the dehydrated garlic slice significantly reduced(P<0.05)with the increase of ozone concentration and treatment time.When the ozone concentration was 30 mg/m3 and the processing time was 90 min,the anti-bacteria effect was best.Under this condition,the total number of colonies was 3.98 log(cfu/g),which was decreased by 0 9 log(cfu/g)compared with the control group.When ozone treatment time exceeded 90 min,there was no significant change in bactericidal effect(p<0.05).During ozone treatment,there was no significant change in garlic allicin content,moisture content,rehydration ratio,protein content and color.2.150 g of dehydrated garlic slices was put on the gauze and then placed in high pressure steam boiler for processing.Processing time ranged from 1 to 9 min and the temperature range was between 105-115 ?.The results showed that:when the steam processing time or steam temperature rose,the total number of colonies declined.When the temperature was 110 ?and the time was 9 min,the total number of colonies reached a minimum value(3.53 log cfu/g),which was reduced by 1.36 log(cfu/g).With the increase of steam treatment time,the color of dehydrated garlic changed markedly.When the processing temperature was 105 ? and processing time exceeded 5 min,dehydrated garlic slice color changed.When processing time reached 9 min,?E was 3,40 and a significant difference in color was observed.At 110 ?,the recovery of dehydrated garlic slice decreased with the increase of steam treatment time.When the treatment time was 9 min,the ratio decreased from 2.61%to 2.49%,although the change was not significant.Superheated steam had a certain effect on the protein content of dehydrated garlic tablets,and the soluble protein content decreased from 22.03%to 20.03%after treatment at 110 ? for 9 min.After heat steam treatment,garlicin significantly declined,and HPLC method cannot detect it when the heating time was over 5 min.Therefore,although the superheated steam can effectively reduce microorganisms in garlic slice,the destruction of sensory and Allicin garlic was severe.3.In order to find the best way to reduce microorganisms,the single factor and L9(34)orthogonal experimental design were applied in this study.The results showed that ozone combined with superheated steam treatment had a good bactericidal effect.After ozone treatment at 30 mg/m3 for 30 min followed by 115 ? steam treatment for 1 min,the total number of colonies was 1.813 log(cfu/g).The results showed that the steam temperature was the principal factor during extraction,followed by ozone duration,ozone concentration andsuperheated steam treatment time.Although the combination of ozone and superheated steam led to the change of color,the ?E between processed group and control group was less than 3,indicating no color difference.Meanwhile,rehydration ratio and the content of soluble protein would change,but the changes were not significant.The optimal group of rehydration.ratio was 2.55 and soluble protein content was 21.86%.Compared with the control group,there were no significant change in both parameters.In addition,allicin content decreased by 0.087%,being 0.054%.