| Because of the advantages of refreshing taste,chewy and pure wheat odor,semi-dried noodle(SDN)is more and more popular.However,the relatively high water content and abundant nutrients could promote microbial growth and reproduction,accelerate the quality deterioration,and shorten its shelf-life.Moreover,the surface of SDN prepared by conventional dehydration process could be hardened and easily broken when bended.In order to better solve the present problems of SDN,this paper tried to find effective ways to prolong its shelf-life by using slightly acidic electrolyzed water,increasing dehydration temperature and prolonging dehydration time,adding bio-inhibitor and alcohols.Effects of alcohols on the hardening improvement of SDN were also investigated preliminarily.Firstly,effects of slightly acidic electrolyzed water(SAEW)on the initial bacterial content and quality of SDN were investigated.The results showed that SAEW significantly(p?0.05)reduced the initial bacterial content of SDN.When the SAEW concentration reached 70 mg/L,the initial total plate count(TPC)of SDN decreased 1.27 lgCFU/g.The results of gelatinization properties showed that SAEW slightly increased the peak gelatinization temperature(T_p)and conclusion gelatinization temperature(T_c)of SDN.In addition,SAEW significantly(p?0.05)increased the hardness and tensile force of SDN,and extended its shelf-life by 15 days at 4?.Meanwhile,SAEW repressed the pH change of SDN during storage.Secondly,effects of increasing the dehydration temperature and prolonging the dehydration time on the initial bacterial content and quality of SDN were investigated.The results showed that increasing the dehydration temperature(105°C to 135°C)significantly(p?0.05)reduced the initial number of mold,yeast and thermophilic bacteria on the SDN.Prolonging dehydration time(205 s to 330 s)reduced the TPC and bacillus number in the SDN by 1.57 lgCFU/g and 0.37 lgCFU/g respectively.And extending the dehydration time to 290 s extended the shelf-life of SDN for 30 days.The two dehydration processes significantly(p?0.05)reduced the gelatinization enthalpy(?H)of SDN,and improved the cooking and texture characteristics of SDN to varying degrees.Scanning electron microscopy(SEM)results showed that the two dehydration processes affected the surface and internal microstructure of the SDN.In addition,effects of adding bio-inhibitor on shelf life and quality of SDN were investigated.The results showed that 0.01%(w/w)?-polylysine hydrochloride(?-PLH)and0.02%(w/w)nisin(Nisin)extended the shelf-life of SDN to 15 days and 10 days,respectively.The compound addition of 0.01%?-PLH and 0.02%Nisin could prolong shelf-life by 21 days.Compound biological antimicrobial agents could actively inhibit the growth of bacillus in SDN,which could delay the rising trend of the TPC of SDN during storage.At the same time,the addition of the biological antimicrobial agents significantly delayed the rate of changes in acidity,pH and overall acceptability of SDN during storage.Finally,effects of adding alcohols on the shelf-life and quality of SDN were investigated.The results showed that 2%(w/w)sorbitol could extend the shelf-life of SDN for 14 days,while2%(w/w)ethanol and 2%(w/w)propylene glycol could extend the shelf-life of SDN by 49days and 42 days,respectively.Meanwhile,the addition of ethanol leaded to the shift of the gelatinization peak of SDN,which reduced the?H of SDN and increased the cooking loss of SDN.The addition of ethanol caused SDN to be brittle and easily broken.SEM results showed that the addition of ethanol had a greater degree of damage to the internal structure of SDN.However,propylene glycol and sorbitol delayed the hardness of SDN during storage.Further analysis found that propylene glycol and sorbitol increased the bound water content,free sulfhydryl content,?-turn structure and protein extractability of SDN. |
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