| Garlic（Allium sativum L.）is an ancient medicinal and edible plant,which has been widely concerned and favored by people for its nutritional value and health care functions.Garlic is one of the important vegetables and cash crops in our country.Garlic occupies an important position in the vegetables in our country and is an important source of increasing farmers’income.Garlic is usually processed into various garlic products to improve its utilization value.Dehydrated garlic slices and garlic powder are important garlic export products in China.The dried products obtained by hot air-drying method can completely retain the effective components of fresh garlic,but there are often have the problems of insect eggs and microorganisms exceeding the standard,which seriously affects the export of dried garlic products in China and the health of consumers.Therefore,further research on bacteria reduction technology to produce high-quality,safe and economical dried garlic slices and garlic powder is of great significance for increasing the farmers’income and prospering our economy.In this paper,the optimal technology for reducing bacteria of garlic powder by ozone,ultraviolet and their combined treatment was studied;The effects of ozone,UV and ozone combined UV treatment on the main quality indexes of garlic slices and garlic powder were studied;Qualitative and quantitative research on flavor compounds of untreated and ozone combined UV treated garlic powder.The main results are as follows:（1）On the basis of the single factor experiment,response surface experiment was used to optimize the sample thickness,ozone concentration and treatment time,it was concluded that the best process of ozone sterilization was as follows:the thickness of garlic powder was 2mm,the ozone concentration was 120 mg/m~3,the treatment time was 28 min,the sterilization rate was 84.01%.At this time,the total number of colonies was 5.03 lg（CFU/g）,which decreased by 0.80 lg（CFU/g）compared with the controls.Applying this method to garlic slices,the total number of colonies in garlic slices after treatment was 4.81 lg（CFU/g）,which decreased by 0.59 lg（CFU/g）compared with the control group.After ozone treatment,the product reached a low microbial level,and there was no significant change in color,water content,rehydration ratio and allicin content.（2）On the basis of the single factor experiment,response surface experiment was used to optimize the sample thickness,irradiation distance and irradiation time,the best process of UV sterilization was as follows:the sample thickness was 2 mm,the irradiation distance was14 cm,the treatment time was 43 min,the sterilization rate was 88.82%.At this time,the total number of colonies was 4.87 lg（CFU/g）,which decreased by 0.95 lg（CFU/g）compared with the control group.Applying this method to garlic slices,the total number of colonies in garlic slices after treatment was 4.86 lg（CFU/g）,which decreased by 0.62 lg（CFU/g）compared with the control group.The product reached a low microbial level after UV treatment,and there was no significant change in color,water content,rehydration ratio and allicin content.（3）On the basis of ozone and UV single factor experiment,the two sterilization methods were combined.Ozone concentration,ozone time,UV irradiation distance and UV irradiation time were selected for orthogonal experiment,and the best combination was obtained:ozone concentration 140 mg/m~3,ozone time 30 min,UV irradiation distance 15 cm and UV irradiation time 40 min,the sterilization rate was 99.93%.At this time,the total number of colonies was 2.65 lg（CFU/g）,which decreased by 3.18 lg（CFU/g）compared with the control group.Applying this method to garlic slices,the total number of colonies in garlic slices after treatment was 2.63 lg（CFU/g）,which decreased by 2.78 lg（CFU/g）compared with the control group.After combined treatment,the product reaches ultra-low microbial level,and there was no significant change in color,water content,rehydration ratio and allicin content.（4）Effects of ozone combined with UV treatment on flavor compounds of garlic powder.Thirty volatile components were identified in the garlic powder before and after sterilization,mainly including aldehydes,ketones,sulfur-containing compounds,esters,and alcohols.There were some differences in the flavor substances in garlic powder before and after the combined sterilization treatment.After garlic powder was treated by ozone combined with UV sterilization,the types of sulfur-containing compounds did not change,but the overall content decreased,and the content of aldehydes and ketones increased.Therefore,after the combined sterilization treatment,the garlic powder still retains the unique flavor of garlic,which reduces part of the pungent and irritating odor and increases the fragrance. |
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