Establishment Of Shelf-life Prediction Model And Optimization Of Positive And Negative Pressure Production Technology For New Radish Pickles

Sichuan pickle,has a long history,is sweet,sour,refreshing and appetizing.Sichuan pickle is honored as “the Bone of Sichuan Cuisine”.Due to the limitation of scientific cognition,the development of Sichuan pickle is slow and production quality is unstable.The production has the characteristics of high content of salt and nitrite and onlinemonitor is difficult.Its production process which stills maintain natural inoculation,natural fermentation stage andmanual operation has great impact on the environment with the high salt wastewater producing,so the traditional pickle industry chain's promotion is also imminent.In order to solve these problems,this paper had developed a new radish pickle process,that was achieved by using drying to replace the traditional salted dehydration,fermentation broth preparation,positive and negative pressure infiltration technology.For the first time,the spicy substances in radish were detected by technical means and the physical methods were used to get rid of the spicy substances in radish.Firstly,the drying time of radish drying to the target moisture at different temperatures and the drying rate of radish at different stages were obtained by drawing the moisture content and drying rate of radish at different temperatures.According to rehydration ratio,total carbohydrates and vitamin C content and SEM observation results,it showed that the optimum drying temperature for radish was 70 ?.The drying kinetics model of radish at different temperatures was:,r...,0.76580.0057 0.0002.This model exhibited the good reliability.The results of verification experiment showed that the actual value of the experiment was consistent with the predictive value of the model which could be used to describe the changes of moisture content of drying radish at different temperatures.Secondly,head space solid phase microextraction method(HS-SPME)was used to extract volatile spicy compounds of radish,the extracted compounds were separated by gas chromatography mass spectrometry(GC-MS).The main volatile and spicy flavor compounds in the radish were sulfur compounds and alcohols.At the end of the fermentation,it was not possible to detect the spicy substances of radish by sensory evaluation.The nonvolatile spicy compounds in radish was detected by silver nitrate titration and the content of it in radish was 0.425%.Through water immersion,low-temperature blanching and salting,the content of nonvolatile spicy substances in radish was reduced by 48.94%,thus improving the taste and sensory quality of the new radish pickle.Moreover,the factors such as garlic,pepper,ginger,millet pepper,sugar candy,cold water,microbial inoculum and salt content were studied by Design-export software.The Placket-Burman design selected for fermentation broth sensory evaluation was remarkable affected by the three factors of millet pepper content,microbial inoculum content,salt content.By the steepest climbing experiment,Placket-Burman experiment and Box-Behnken experiment,the best formula of fermentation broth was as follows: salt 30 g,microbial inoculum 0.5g,millet pepper 15 g,garlic 5g,celery 15 g,onion 20 g,ginger 5g,cold water 200 g,sugar candy 20 g,bay leave 1 piece,illicium verum 1 piece,cold water 800 g,sensory scores were above 85.Then,based on fuzzy sensory evaluation,the positive pressure,vacuum degree,processing time and solid-liquid ratio were investigated by single factor experiment and orthogonal experiment.The optimum processing of new type of radish pickle was obtained as follows: positive pressure 12 MPa,vacuum degree-0.08 kpa,processing time 15 min and solid-liquid ratio 1:2.Positive and negative pressure infiltration equipment which consisted of positive and negative pressure chamber,pressurization system,vacuum system,heating system,mixing system,inlet and outlet system had the characteristics of automatic temperature control,automatic heating,wide range of applications,etc.Finally,through the analysis of accelerated shelf life testing(ASLT)and the coefficient of variation,it could be obtained that the hardness of new radish pickle could be used as the index of the quality changes of the new type of pickle during the storage.The shelf life model of the new type of pickle was as follows: y=173.36e-0.7084x(R2=0.9963).The predictive shelf life of the new type of pickle was 130 days at 4?,and the actual shelf life was 132-136 days.The error was 3.65%,which indicated that the model was accurate.The new radish pickle's production quality standards were set up,which provided a theoretical basis for industrial production in the future.