Study On Influences Of Konjac Glucomannan-nano Si O2 Film-coating On The Freshness Preservation Effects Of Physalis Pubescens At Room Temperature

ObjectivePhysalis pubescens was studied in this article to investigate the influences of konjac glucomannan-Nanometer SiO₂ film-coating?KGM/nano-SiO₂?on the freshness preservation effects of Physalis pubescens at room temperature,for the purpose of providing an experimental basis for the freshness preservation of Physalis pubescens.MethodsThe influences of KGM/nano-SiO₂ film-coating on the physicochemical property and active substance of Physalis pubescens during its storage period were analyzed by measuring a series of indicators concerning Physalis pubescens,such as rotting rate,weight-loss rate,total soluble solid?TSS?,titratable acid?TA?,vitamin C?Vc?,content change of total phenols and flavones.Texture analyzer and the method of texture profile analysis?TPA?were employed to study the changes of film-coated Physalis pubescens in terms of its hardness,resilience,elasticity,coherency,viscosity and chewiness.Meanwhile,correlations between each texture parameter were also analyzed.Electronic nose was employed to monitor the smell changes of film-coated Physalis pubescens.Methods of radar chart,principal component analysis?PCA?and linear discriminant analysis?LDA?were applied to analyze Physalis pubescens during its storage period about the trend of its smell changes,majoringredients and the influences of film-coating on the smell preservation.The influences of KGM/nano-SiO₂ film-coating on the anti-aging effects of Physalis pubescens were investigated by analyzing the activity changes of polygalacturonic acid?PG?,polyphenol oxidase?PPO?,lipoxygenase?LOX?and peroxidase?POD?during the aging process of Physalis pubescens.ResultsThe rotting rate of Physalis pubescens preserved at room temperature was significantly reduced by using the KGM/nano-SiO₂ film-coating.Ater a storage period of 29 days,compared with the control group,the rotting rate of the film-coating treatment group with 0.4%KGM+0.01%nano-SiO₂ was decreased by a maximum level of 31±1.2%.Meanwhile,the film-coating could bring down the loss of moisture for Physalis pubescens,decrease its weight-loss ratio,effectively prevent the rising of total soluble solid for fruits,slow down the consumption of titratable acid and help preserve the Vc contents in Physalis pubescens to a certain extent.After film-coating treatment,the arrival of peak accumulation volume of phenolic ketone active substances contained in fruits of Physalis pubescens was delayed by 2 days and the loss of phenolic ketone in fruits was reduced.At the later stage of storage?29 d?,after treated by0.4%KGM+0.01%nano-SiO₂ and 0.6%KGM+0.01%nano-SiO₂,the contents of flavones and total phenols for the treatment group were respectively 1.43 times and 1.41 times of that for the blank control group.In line with the texture analysis,the hardness,resilience,elasticity,coherency,viscosity and chewiness were properly kept by the KGM/nano-SiO₂film-coating treatment of different concentrations in a good status for fruits of Physalis pubescens.The analysis on the correlations between each indicator showed that hardness maintained a significantly positive correlation with resilience,elasticity,coherency,viscosity and chewiness?R2=0.725-0.995?.It was found from the analysis results of electronic nose and radar map thatthe fragrance emitting of Physalis pubescens fruits could be effectively delayed by the KGM/nano-SiO₂ film-coating.The major fragrant ingredients of Physalis pubescens include terpenoid and oxynitride.In an unsealed open space,the fragrant ingredients of Physalis pubescens in each film-coating treatment group were gradually decreased,reaching its maximum loss on the 10 th day.From then on,the loss was increasingly declined.PCA and LA analysis further indicated that there were no obvious changes for volatile ingredients of Physalis pubescens in each treatment group.And the film-coating treatment could exert remarkable influences on the volatilization of gragrance for Physalis pubescens fruits.By putting off the arrival of activity peaks for peroxidase?POD?,polygalacturonic acid?PG?and polyphenol oxidase?PPO?during the aging process of fruits,the film-coating treatment group with0.4%KGM+0.01%nano-SiO₂ could suppress lipoxygenase's?LOX?activity to minimize damages for peroxidating free radical,prevent softening and loss of flavor substances for fruits and delay their aging process.ConclusionsPhysalis pubescens,treated by 0.4%KGM+0.01%nano-SiO₂ film-coating technique for the purpose of preserving it at room temperature,could remarkably bring down the rotting rate and loss of moisture and titratable acid for Physalis pubescens fruits,prevent rising of total soluble solid,delay the arrival of peak accumulation volume of phenolic ketone substances,decrease the loss of Vc and phenolic ketone in fruits,preserve the texture properties of Physalis pubescens fruits,and significantly delay the volatility of fragrant substances in Physalis pubescens fruits.In the mean time,there were no significant color differences for Physalis pubescens fruits in both control group and treatment group.By postponing the arrival of activity peaks for POD,PG and PPO,LOX's activity was suppressed by the treatment with0.4%KGM+0.01%nano-SiO₂,which would help minimize damages for peroxidating free radical,prevent softening and loss of flavor substances for fruits and delay their aging process.Compound film-coating agent with0.4%KGM+0.01%nano-SiO₂ proved the best preservation performance.