Arup Jyoti Das

Modeling and optimization of the process parameters in vacuum drying of culinary banana (Musa ABB) slices by application of artificial neural network and genetic algorithm

ABSTRACT The influence of drying temperature, sample slice thickness, and pretreatment on quality attributes like rehydration ratio, scavenging activity, color (in terms of nonenzymatic browning), and texture (in terms of hardness) of culinary banana (Musa ABB) has been evaluated in the present study. A comparative approach was made between artificial neural network (ANN) and response surface methodology (RSM) to predict various parameters for vacuum drying of culinary banana. The effect of process variables on responses during dehydration were investigated using general factorial experimental design. This design was used to train feed-forward back-propagation ANN. The predictive capabilities of these two methodologies for optimization of process parameters were compared in terms of relative deviation (Rd). Results revealed that a properly trained ANN model is found to be more accurate in prediction as compared to RSM. The optimum condition selected from ANN/GA responses on the basis of highest fitness value revealed that culinary banana slices of 6 mm thickness pretreated with 1% citric acid and dried at 76°C resulted in a maximum rehydration ratio of 6.20, scavenging activity of 48.63% with minimum nonenzymatic browning of 25%, and hardness of 43.63 N. Results further revealed that, in the case of rehydration ratio, temperature and pretreatment showed a positive effect while thickness had a negative effect. On the contrary, for scavenging activity, temperature showed the highest negative effect followed by slice thickness and positive effect with pretreatment. For nonenzymatic browning, thickness showed the highest negative effect but temperature and pretreatment showed a positive effect. Similarly, for hardness, all three parameters showed a negative effect.

In Vitro Antioxidant Activities of Polyphenols Purified from Four Plant Species Used in Rice Beer Preparation in Assam India

The purified phenolic extracts of Artocarpus heterophyllus, Oldenlandia corymbosa, Cyclosorus extensa, and Alpinia malaccensis were tested for the presence of various polyphenols and antioxidant activities. The polyphenols were extracted with ethanol and purified by stepwise dialysis and column elution. High-performance liquid chromatography was performed to detect and quantitate the polyphenols and 10 different in vitro methodologies were used to measure antioxidant properties. Quercetin, ferulic acid, and salicylic acid were present in all the species. Chlorogenic and p-coumaric acid in A. heterophyllus; p-coumaric acid, caffeic acid, naringin, catechol, and resorcinol in C. extensa; chlorogenic, caffeic, and quinic acid in O. corymbosa and naringin, quinic acid and catechol in A. malaccensis were detected with varied concentrations. The 2-deoxyribose, 1,1-diphenyl-2-picryl-hydrazyl and 2,2’-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) assays exhibited high radical scavenging activities and they were also able to combat •OH radicals and H2O2 to an extent of 25.53 and 71.23% respectively. Superoxide anions and nitric oxide radicals were scavenged up to 63.85 and 56.24%, respectively, and the extracts exhibited ferric ions chelation and ferrous ions reduction capacity. A reduction in the level of lipid peroxidation was also observed. All four species were found to be potent sources of polyphenols having antioxidative property. The results fully justified the use of these plants in the beer making process of Assam, India.

Drying Characteristics and Assessment of Physicochemical and Microstructural Properties of Dried Culinary Banana Slices

Abstract This study quantifies the drying characteristics and quality attributes of culinary banana at various temperatures (40–70°C) which exhibited falling rate period. Among the different drying models, Wang and Singh model was found the best fitted model with lowest Ӽ2 and highest R2 values. The coefficients of Wang and Singh model were expressed in nonlinear form as a function of temperature and a new model was developed in which moisture ratio is expressed as a function of time and temperature. Effective moisture diffusivity increased with increase in drying temperature. Scanning electron micrographs showed that samples dried at 70°C produced larger pores which resulted in better rehydration ratio and minimum hardness. The nonenzymatic browning occurred faster at 70°C and in addition, the chemical properties were not significantly affected by drying temperatures.

Phytochemical Constituents, Attenuated Total Reflectance Fourier Transform Infrared Analysis and Antimicrobial Activity of Four Plant Leaves Used for Preparing Rice Beer in Assam, India

Phytochemicals content and antimicrobial activity of Artocarpus heterophyllus, Cyclosorus extensa, Oldendia corymbosa, and Alpinia malaccensis were investigated. Maximum alkaloids and terpenoids were found in A. heterophyllus; tannins and saponins in C. extensa; flavonoids, polyphenols, and phytosterols in O. corymbosa and anthraquinone, glycosides, and anthocyaninin A. malaccensis. Aqueous, methanolic, ethyl acetate, and hexane extracts were prepared from all the leaves. Attenuated total reflectance Fourier transform infrared spectrophotometric (ATR-FTIR) analysis revealed that alkanes and alkyl halides were prevalent in all the extracts and the ethyl acetate extracts contained comparatively higher number of functional groups, which were also more effective against Candida albicans, Escherichia coli, and Staphylococcus aureus. The minimum inhibitory concentration values of A. malaccensis against the tested pathogens were found to be lesser than the other species.

Amylolytic fungi in starter cakes for rice beer production

Two types of starter cakes, viz. amou and perok-kushi, used in the production of rice beer in Assam, India, by the Bodo and Deori communities, respectively, were used for the isolation of amylolytic fungi. Based on the sequencing of their internal transcribed spacer (ITS) regions the fungi were identified as Amylomyces rouxii and Rhizopus oryzae, and given the strain names TU460 and TU465, respectively. Both the strains showed the ability to degrade and saccharify starch. The glucoamylase activity was considerably high in A. rouxii TU460 (14.92 μmol/min) as compared to R. oryzae TU465 (1.41 μmol/min), whereas α-amylase activity was found to be closely related, i.e. 7.02 and 6.09 unit mL-1, respectively. SDS PAGE for the determination of the molecular size of the glucoamylase enzymes revealed the production of two distinct units of 59 kDa and 31 kDa by A. rouxii TU460, and one unit of 72 kDa by R. oryzae TU465. LC MS/MS analysis revealed that no mycotoxins were produced by either of the strains. The overall study indicated a good amylolytic property of both strains and a potential for application in the starch processing industries.

Optimization of the extraction of phenolic compounds from Cyclosorus extensa with solvents of varying polarities

ABSTRACT The leaves of Cyclosorus extensa are used in the preparation of rice beer in Assam, India. The optimal conditions of time and temperature of fermentation for extraction of bioactive compounds from the dried leaves were obtained using response surface methodology. The central composite rotatable design was used and 13 experimental runs based on two-factor-five-level design were generated and performed for each of the solvents. The independent variables were extraction time (12 and 48 h) and temperature (25 and 55°C). The responses studied were total polyphenol content, radical scavenging activity, antibacterial activity, and antifungal activity. The analysis of variance of the test data was performed and the sequential sum of squares, F-value, R2, and adjusted R2 were deduced. The predicted models for all the response variables were adequately fitted to the observed experimental data (p ≤ 0.001). The maximum extraction of bioactive compounds under the optimum conditions of extraction temperature and time for hexane, ethyl acetate, methanol, and distilled water were found to be 25°C for 29.43 h, 28.28°C for 41.27 h, 43.95°C for 29.61 h, and 55.00°C for 48.00 h, respectively. It was also observed that the solubility of the polyphenols was higher in methanol, followed by ethyl acetate, and the highest antibacterial activity against Escherichia coli was shown by the ethyl acetate extracts.