Study On Formation And Control Of Flavour Deterioration And Non-Enzymatic Browning Of Cloudy Bayberry Juice

Cloudy bayberry juice, with rich nutritional compositions and unique flavour, is popularto Chinese consumers. However, cloudy bayberry juice usually suffers from off-flavourproblems during processing&storage. Another striking problem for the production of cloudybayberry juice is non-enzymatic browning. In ordor to improve cloudy bayberry juice quality,this paper analyzed the causes of off-flavour and non-enzymatic browning, then put forwardthe corresponding improved measures. The flavour and colour of cloudy bayberry juice wasimproved by a series of control measures.Firstly, in ordor to study flavour change of cloudy bayberry juice during processing&storage, its aroma components, physicochemical characteristic and sensory evaluation werecomparatively analyzed. The results showed that the contents of esters, alcohols, total sugarand titratable acidity of the raw juice with rancid flavour (RF) are, respectively,6.03%,8.24%,5.56g/L,0.18g/L less than that of good flavour raw juice (GF), while the contents ofaldehydes is4.19%higher than that of GF. Compared with appropriate heat-treatment (AF),warmed-over treatment (WF) caused esters, total sugar and titratable acidity respectivelydecreases6.19%,4.88g/L and0.13g/L. It also caused the generation of dimethyl sulfoxide.Compared with newly produced juice (NF), the cloudy bayberry juice producedfermentation-like flavour (FF) with alcohol increases (11.51%) as well as esters (14.91%) andtotal sugar (3.27g/L) decreases.Secondly, in ordor to improve off-flavours, suitable processing and recipe were choosed:(1)5-10mg/kg ethyl maltol could improve warmed-over flavour and keep good quality;Warmed-over flavour also could be improved by adding β-cyclodextrin. However,β-cyclodextrin had negative affect on suspension stability and color of cloudy bayberry juice.(2) Extending the degassing time to45s made esters (19.06%) increases and alcohols(17.26%) decreases, then inhibited the generation of fermentation-like flavour.Thirdly, in ordor to study the mechanism of non-enzymatic browning of cloudy bayberryjuice during storage, the changes of browning index (A420), chroma difference and severalmain browning factors of cloudy bayberry juice were investigated by correlation and pathanalysis. The results of path analysis showed that oxidation and polymerization of phenolswas a chief element for non-enzymatic browning of cloudy bayberry juice during storage at25°C. When at37°C, the major reasons were oxidation and polymerization of phenols andMaillard reaction. The results of correlation analysis between phenols and browning index,chroma difference showed that the accumulation of anthocyanins was the most importantfactor for non-enzymatic browning of cloudy bayberry juice during storage.After that, the effect of juice pH, color fixative and illumination intensity onnon-enzymatic browning of cloudy bayberry juice were researched. The results showed thatjuice pH had an effect on non-enzymatic browning of cloudy bayberry juice during storage,the juice browning decelerated when juice pH lowed;0.2g/L phytic acid, L-Cys and rutincould improve anthocyanin retention rate (16.18%,19.34%and22.32%, respectively) andhad good inhibition effect on non-enzymatic browning of cloudy bayberry juice duringstorage; The greater the intensity of the light led to deeper browning.Finally, the quality of bayberry juice was improved by addition5mg/kg ethyl maltol and 0.2g/L rutin as well as extending the degassing time to45s. Compared with controls, theimprovement measures made the bayberry flavour enhanced, the warmed-over andfermentation-like flavour weaken, total sugar (3.77%) and titratable acidity (5.13%) increased,A420decreased, the value of a*increased and anthocyanin (3.86mg/100mL) increased.