Study On Foundational Theory And Technology Of Avocado Jam Based On High Pressure Processing

Avocado contains abundant nutrition,which can not be stored for a long time.At present,avocado were consumed by fresh mostly.Although it possesses high nutrition,its tastes was not cater to Chinese.Therefore,improving avocado’s flavor and developing new products is particularly important.Jam has abundant nutrition and great taste,is an important processing direction for fruits and vegetables now.This paper produced an avocado jam,which taken fresh avocado as raw materials.The process parameters were determined after a group of tests,applying HPP to sterilize for jam.Compared with pasteurization and autoclaving to evaluate HPP well,measure the microbiological and physicochemical related indexes of avocado jam,and the changes of the microbiological and physicochemical related indexes during storage to select the best pressure and dwell time to sterilize.In addition,to reduce influence on jam from the property changes of the materials during HPP treatment and storage,the paper contrasts some main materials(Polyamide PA,Polypropylene,Co-extruded composite)that are suitable for HPP at present,researches barrier and mechanical property under HPP.The main results of the paper are as follows:(1)The most optimal parameters of avocado jam:ratio of avocado and water was 2:1,potassium sorbate ratio was 0.04%;sugar ratio was 23%;citric acid ratio was 0.7%;thickener ratio was 0.5%according to the ratio of low methoxy pectin and xanthan gum was 1:2,the time of jam concentrated was 20 min.(2)During the rise of pressure and continual dwell,the number of total bacterial colonies decreased,after 300MPa/15min HPP treatment,the number decreased obviously.300MPa/15min,400MPa/5min and 500MPa/5min could kill all coliforms.300MPa/5min could make the number of mold and yeast colonies arrive commercial asepsis,300MPa/15min could kill all mold and yeast colonies.Pressure had an evident effect on mold and yeast,coliform,continual dwell had no evident effect.(3)Brix,pH of avocado jam had no change after different pressure and dwell time treatment.Pressure elevate,total acid increased,?E and viscidity had no evident fluctuation,but total sugar declined.Under continual dwell,total acid declined and?E rised,but total sugar had no evident difference,viscidity fluctuated irregularly.V_C declined with the rise of pressure and continual dwell,while exceeded pasteurization and autoclaving.(4)During storage,the number of total bacterial colonies increased after100~300MPa/5min and pasteurize treatment,others had no evident change.The number of coliforms had no evident change after 200~500MPa/5min and autoclave treatment.The number of mold and yeast colonies had no evident increase after 300~500MPa/5min treatment.The number of total bacterial colonies increased slightly after 300MPa/15min treatment,it had no evident difference with the increase of dwell time.Dwell time had no significant effect on the number of coliforms.The number of mold and yeast colonies increased slightly during terminal storage after 300/15min and 300/20min.(5)During storage at 4℃,Brix,pH of avocado jam had no change after different pressure and dwell time treatment.V_C declined but exceeded pasteurization and autoclaving.The increase of pressure and dwell time could restrain degradation of V_C.?E increased but had no obvious difference between different pressure.?E had the most obvious change after autoclave treatment.The increase of dwell time could restrain the change of color.Viscidity had no obvious change after HPP.Viscidity changed evidently after pasteurize and autoclave treatment.Total acid and total sugar respectively increased and decreased after different pressure treatment,the speed of change descend with the increase of pressure.Total acid and total sugar were free from different dwell time.By all-sided consideration,300MPa/15min had a better effect on sterilizing and keeping quality for avocado jam.(6)After different pressure treatment,the gas permeability of PP fluctuated up and down,PA and co-extruded composite had smaller change,moisture permeability of PA10c and o-extruded composite 10c was basically stable,amount of water vapor of PA10c was smaller,other materials all had a certain degree of change.After different dwell time treatment,the gas permeability of PP declined,especially under 10 and 15min.The gas permeability of PA were inferior to control group,co-extruded composite had no evident increase.Moisture permeability of PA remained steady mainly,PP and co-extruded composite material fluctuated obviously within 20min.After HPP treatment,the tensile strength of PA8c declined,PP and co-extruded composite increased,but all materials had no apparent change as pressure increased.Under 200MPa,elongation at break of co-extruded composite 10c and PA8c increased obviously,then had no obvious change,other materials had no significant difference as pressure change.After 300MPa treating5~20min,the tensile strength of PP4c and PP5c was larger at 10min,PA8c declined and increased,PA10c changed not obviously,the tensile strength of co-extruded composite had no significant difference as dwell time changed.Dwell time had no obvious effect on elongation at break.By all-sided consideration,PA10c was the best material.