Study On Process Optimization And Quality Characteristics Of Black Garlic Prepared By Wushan Purple-red Garlic

Garlic,as a kind of medicinal and edible substance with high nutritional value,has been widely used.However,garlic has high water content and is not resistant to storage.It is a semi-perishable substance^[1].So it is very important to discuss the deep processing of garlic and extend the garlic industry chain.Black garlic is a new garlic deep-processing product,which is concerned as a healthy food because of its unique flavor,good preservation and convenient eating.Nowadays,black garlic is mainly fermented under high temperature and high humidity conditions.The longer fermentation time makes it difficult to control the quality and increase the production cost.This study took chongqing wushan amaranthus garlic rich in allicin as raw material,mainly studied the optimization of garlic pretreatment to shorten the fermentation time of black garlic,and studied the quality characteristics of black garlic,providing reference for the intensive processing and industrial production of wushan amaranthus garlic.The main research contents and results are as follows:1.Optimization of pretreatment conditions on the quality of fermented garlicWushan garlic was pretreated by low-temperature freezing,microwave and ultrasonic respectively.The changes of nutritional quality and physical properties were studied under different pretreatments,so as to determine the optimal process parameters of low-temperature freezing,microwave and ultrasonic pretreatments.(1)The results of low temperature pretreatment showed that the content of each component of garlic pretreated at 4?and 0?was little different from that of fresh garlic,but at-20?and-40?,the water content and texture parameters of garlic decreased with the increase of treatment time,the degree of fragmentation and color difference increased with the increase of time,and the chemical quality components showed the trend of first rising and then falling,and the treatment 1-3 d,The content of allicin was higher at 0.5 d and total polyphenols was higher at 2 d.Therefore,the pretreatment condition of garlic was determined to be-20?for 2 days.(2)The results of microwave pretreatment showed that there was no significant change in the color of garlic cloves after microwave treatment.The higher the microwave power or the longer the treatment time,the lower the water content,the specific degree of cell fragmentation,the lower the content of allicin,the smaller the hardness,and the fluctuation trend of viscoelasticity and chewability.The contents of soluble sugar,total acid,amino nitrogen and total polyphenols were appropriate when treated for 10s under 400W,640W and 800W condition.Therefore,the microwave pretreatment condition of garlic was determined to be 640W for 10 s.(3)Results of ultrasonic pretreatment:according to the single factor experiment,the ultrasonic time(0.5 h,1 h,1.5 h),power(200W,300W,400W)and ultrasonic temperature(10?,20?,30?)were selected to carry out the orthogonal experiment of three factors and three levels,and the ultrasonic pretreatment conditions of garlic were determined as 300 W,40?for 0.5 h.2.Optimization of fermentation technology of garlic with different pretreatment and its effect on the quality of garlicAccording to the above pretreatment optimization process,we can get the best pretreatment conditions of three ways.On this basis,we prepare fermented black garlic,and study the influence of different fermentation temperature and humidity on the quality of black garlic,and then select the optimization process of three pretreatment methods.(1)The results showed that the water content decreased first and then increased slightly with the increase of time;the texture characteristics of black garlic decreased first and then increased with the increase of fermentation time;the texture of black garlic was soft and waxy after 9 days fermentation at 75?,with the texture of preserved fruit;The content of 5-HMF was suitable for 9-12 days fermentation at 80%RH.Allicin decreased rapidly after 9 days fermentation without pungent taste,and the total polyphenol content of garlic was more than ten times of that of fresh garlic at 80%RH and 90%RH.To sum up,it is the most suitable condition for garlic to ferment at75?and 80%RH for 12 days.(2)The results showed that the change range of water content was large,the texture was suitable for 9-12 days,and there was no significant difference in color difference after 9 days.The contents of soluble sugar,total acid,5-HMF and free amino acid increased with the increase of fermentation time,and the content of flavor components in 9?12d fermentation was appropriate.Allicin decreased with the increase of fermentation time,and the activity of total polyphenol and SOD increased first and then decreased with the increase of fermentation time.In the comprehensive sensory evaluation of black garlic,samples fermented at 75?and 12d at 80%RH were selected.(3)The results showed that the moisture content of garlic was about 30-40%,the viscoelasticity and chewability were appropriate,the content of soluble sugar increased first and then decreased,the total acid accumulation increased,the content of 5-HMF and free amino acid increased first and then decreased with the increase of fermentation time,75?and 70-80%RH fermentation 9-12 d had lower allicin content,higher polyphenol content and SOD activity,so the fermentation conditions of 75?and 70%RH for 9 days were determined.(4)The average sensory score of microwave pretreatment was higher than that of freeze and ultrasonic pretreatment.Combined with the analysis of volatile flavor substances,after high temperature and high humidity fermentation,the kinds of thioether substances in garlic were greatly reduced,the number of irritant odor substances was reduced,the kinds and contents of food aroma components were significantly increased,and the quality of fermented black garlic by microwave pretreatment was better,so the fermentation technology of preparing black garlic by microwave pretreatment was finally selected.3.Quality characteristics and product quality standards of wushan black garlic prepared by microwave pretreatment were establishedTen batches of black garlic products fermented by the best technology were selected.The sensory quality,water content,color,texture,5-HMF,soluble sugar,total acid,free amino acid and microbe related indexes of the products were determined to provide a theoretical basis for the establishment of the quality standard of Wushan black garlic.The results showed that the basic components of Wushan black garlic were water,protein,crude fat,carbohydrate and the ash content was 32.168,9.079,0.294,55.536,and 2.923 g/100g.The quality standard includes sensory quality,physical and chemical indexes and health indexes,among which the sensory description is that the garlic is complete,almost free of micro cracks and other impurities visible to the naked eye;the shell is grayish brown,and the content is black or dark brown;it has a light burnt smell and no peculiar smell;it is slightly sour,sweet,spicy,astringent and bitter;it has a soft,waxy q-shaped taste,not dry,hard and not sticky The main physical and chemical indexes were water content 28%-34%,hardness 104-523 g,total acid content 13.607-19.779 mg/g,soluble sugar content 395.757-452.516 mg/g.The health indicators are colony count?1000 CFU/g,mould?50 CFU/g,and Escherichia coli?10 CFU/g.