Research On Aroma Change And Functional Properties Of Egg White Peptide Powders During Storage

This study was granted by the Key Projects in the National Science & Technology Pillar Program during the Twelfth Five-Year Plan Period(No.2012BAD33B03).In the present thesis,the egg white peptide powders(EWPPs)with molecular weight range from 1 to 3 k Da was taken as material.The headspace solidphase micro-extraction(HS-SPME)conditions were optimized.At the same time,the effects of storage temperature and relative humity(RH)on the volilate components of EWPPs were detected by using HS-SPME-GC-MS,and the key volatile components responsible for the aroma changes were futher identified.In the end,the changes of structure and functional properties were also studied.The main results are as follows:1.The EWPPs with molecular weight range from 1 k Da to 3 k Da was taken as material.The total peak area of volatile components,measured by using HS-SPME conmbined with GC-MS,was selected as evaluation index The best extraction conditions were selected as following: the fiber is 65 μm PDMS/DVB,the extraction temperature was 50 °C,the extraction time was 40 min,and the desorption time was 5 min。2.30 kinds of volatile components was identified in EWPPs during storage,including 5 aldehydes,5 ketones,5 esters,3 aromatic hydrocarbons,3 alkanes,3 alcohols,2 phenols,2 heterocyclic compounds and 2 sulfur-containing compounds.During storage,the total concentration of the carbonyl compounds,the esters,the phenolic compounds and the heterocyclic compounds is larger under the higher RH condition when stored at the same storage temperature.And at the same RH,the storage temperature of 25 °C was more conducive to the generation of carbonyl compounds,heterocyclic compounds and sulfur-containing compounds than 4 °C.With the increase of storage time,the total concentration of carbonyl compounds,hydroxyl compounds,heterocyclic compounds and sulfur-containing compounds tended to increase gradually,and the total concentration of phenolic compounds showed a decreasing trend,while that of the ester compounds and alcohols did not have significant tendency of variation.3.The results of sensory evaluation showed that the EWPPs showed a strong fat odor and it score was 5.42 ± 1.00.With the increase of storage temperature and RH,the intensity of fat flvoar became weaker and the intensity of roasted and rubbery odors became stronger.The EWPPs-IV presented the strongest roasted and rubbery odors and the weakest fat flavor,and their sensory scores were 2.17 ± 0.72,6.42 ± 1.08,and 6.83 ± 1.11,respectively.The results of sensory evaluation showed that storage temperature and RH had significant effects on the aroma changes of EWPPs.Furthermore,the EWPPs stored at the same temperature had similar aroma profiles,which had been confirmed through the relative position of samples in PCA analysis.In Addition,the verification experiment about contributions of volatiles,temperature and RH to the changed aroma were conducted,the results further revealed that 3-ethyl-2,5-dimethyl-pyrazine and benzothiazole may be the key volatiles responsible for aroma changes.4.The antioxidant activity of EWPPs decreased significantly after storage at different conditions.The antioxidant activity of EWPPs-III and EWPPs-IV at 25 °C were both higher than than of EWPPs-II,which may be due to the Maillard reaction.And the antioxidant activity of EWPPs-II was the lowest,the DPPH scavenging activity and ABTS scavenging activity were 31.07 ± 1.55 % and 53.73 ± 0.59 %,respectively.The functional properties,including solubility,emulsifing capacity,emulsifing stability,foaming capacity and foaming stability,decreased gradually in the order of EWPPs,EWPPs-I,EWPPs-II,EWPPs-III and EWPPs-IV.The results indicated that the high temperature and RH had a bad effect on the storage stability of EWPPs.5.After storage at different conditions,the contents of amino acids in EWPPs decreased to some extent.Tryptophan was the main source of endogenous fluorescence,the decrease of its content resulted in a obvious decrease of endogenous fluorescence intensity.The secondary structure of EWPPs changed to random keystone structure after storage,and the stability of EWPPs was decreased,which resulted in the decrease of denaturation temperature.