Optimization of drying process parameters for cauliflower drying

Effect of the Drying Method and Storage Conditions on the Quality and Content of Selected Bioactive Compounds of Green Legume Vegetables

This study aimed to determine the effect of the drying method (freeze-drying, air-drying), storage period (12 months), and storage conditions (2-4 °C, 18-22 °C) applied to two legume species: green beans and green peas. The raw and dried materials were determined for selected physical parameters typical of dried vegetables, contents of bioactive components (vitamin C and E, total chlorophyll, total carotenoids, β-carotene, and total polyphenols), antioxidative activity against the DPPH radical, and sensory attributes (overall quality and profiles of color, texture, and palatability). Green beans had a significantly higher content of bioactive components compared to peas. Freeze-drying and cold storage conditions facilitated better retention of these compounds, i.e., by 9-39% and 3-11%, respectively. After 12 months of storage, higher retention of bioactive components, except for total chlorophyll, was determined in peas regardless of the drying method, i.e., by 38-75% in the freeze-dried product and 30-77% in the air-dried product, compared to the raw material.

Influence of Air-Drying Conditions on Quality, Bioactive Composition and Sensorial Attributes of Sweet Potato Chips

The drying process is an essential thermal process for preserving vegetables and can be used in developing dried products as healthy alternative snacks. The effects of air-drying conditions using a convection dryer with hot air at different temperatures (60°, 65°, 70°, 75°, and 80 °C, in the range 5–200 min, at a fixed air speed of 2.3 m/s) were tested on the quality of slices (2.0 ± 0.1 mm) of dried sweet potato (Bellevue PBR). For each time and temperature, drying condition, physicochemical parameters (moisture content, CIELab color, texture parameters, total phenolic and carotenoid contents) and a sensory evaluation by a panel at the last drying period (200 min) were assessed. Drying time was shown to have a more significant effect than temperature on the quality of dried sweet potato as a snack, except for carotenoid content. Given the raw tuber content, thermal degradation (p < 0.05) of total phenolic compounds (about 70%), regardless of tested conditions, contrasted with the higher stability of total carotenoids (<30%). The dried product, under optimal conditions (≥75 °C for 200 min), achieved a moisture content (≤10%) suitable for preservation, providing a crispy texture with favourable sensory acceptance and providing a carotenoid content similar to the raw product.

Effect of ohmic blanching on drying kinetics, physicochemical and functional properties of garlic powder

This study aims to perform an optimization of process parameter for ohmic blanching of garlic to focus on the drying characteristics of the garlic powder at different temperatures. Comparative analyses on physicochemical and functional properties of differentially blanched garlic powder are carried out. The browning intensity was found to be lesser in garlic with ohmically blanched at 26.66 V/cm for 30 s. Process optimization was carried using different thin layer models, out of which Midilli-Kucuck was found to best fit model (R 2 = 0.9954). Rate of drying was significantly higher in ohmically blanched garlic compared to conventional blanching. Obtained garlic powder by differential blanching methods was analyzed for physicochemical and functional attributes specifically; diallyl disulphide content was retained up to 945.8 mg/kg, 928.7 mg/kg and 667.6 mg/kg, respectively.

Modeling and Optimization for Konjac Vacuum Drying Based on Response Surface Methodology (RSM) and Artificial Neural Network (ANN)

To reveal quality change rules and establish the predicting model of konjac vacuum drying, a response surface methodology was adopted to optimize and analyze the vacuum drying process, while an artificial neural network (ANN) was applied to model the drying process and compare with the response surface methodology (RSM) model. The different material thickness (MT) of konjac samples (2, 4 and 6mm) were dehydrated at temperatures (DT) of 50, 60 and 70 °C with vacuum degrees (DV) of 0.04, 0.05 and 0.06 MPa, followed by Box–Behnken design. Dehydrated samples were analyzed for drying time (t), konjac glucomannan content (KGM) and whiteness index (WI). The results showed that the DT and MT should be, respectively, under 60 °C and 4 mm for quality and efficiency purposes. Optimal conditions were found to be: DT of 60.34 °C; DV of 0.06 MPa and MT of 2 mm, and the corresponding responses t, KGM and WI were 5 h, 61.96% and 82, respectively. Moreover, a 3-10-3 ANN model was established to compare with three second order polynomial models established by the RSM, the result showed that the RSM models were superior in predicting capacity (R2 > 0.928; MSE < 1.46; MAE < 1.04; RMSE < 1.21) than the ANN model. The main results may provide some theoretical and technical basis for the konjac vacuum drying and the designing of related equipment.

Comparison of Traditional and Novel Drying Techniques and Its Effect on Quality of Fruits, Vegetables and Aromatic Herbs

Drying is known as the best method to preserve fruits, vegetables, and herbs, decreasing not only the raw material volume but also its weight. This results in cheaper transportation and increments the product shelf life, limiting the food waste. Drying involves the application of energy in order to vaporize and mobilize the moisture content within the porous products. During this process, the heat and mass transfer occurs simultaneously. The quality of dehydrated fruits, vegetables, and aromatic herbs is a key problem closely related to the development and optimization of novel drying techniques. This review reports the weaknesses of common drying methods applied for fruits, vegetables, and aromatic herbs and the possible options to improve the quality of dried products using different drying techniques or their combination. The quality parameters under study include color, bulk density, porosity, shrinkage, phytochemicals, antioxidant capacity, sugars, proteins, volatile compounds, and sensory attributes. In general, drying leads to reduction in all studied parameters. However, the behavior of each plant material is different. On the whole, the optimal drying technique is different for each of the materials studied and specific conditions must be recommended after a proper evaluation of the drying protocols. However, a novel or combined technique must assure a high quality of dried products. Furthermore, the term quality must englobe the energy efficiency and the environmental impact leading to production of sustainable dried products.

Parametric optimality of tray dried Musa balbisiana Colla blossom

Musa balbisiana Colla blossom has enriched applications as a key constituent of dried vegetable formulations. With restricted prior art, the article addresses the optimality of tray drying characteristics of the blossom from both statistical design and drying kinetics perspective. The process variables in due course of optimization refer to moisture content, antioxidant activity and vitamin C for variation in drying time and temperature. Model fitness, analysis of variance based analysis and numerical optimization were considered during the statistical design of experiments. Drying kinetics involved fitness studies of alternate models, moisture diffusivity and process variable characteristics. Thereby, the sensitivity of both approaches to obtain optimal parameters associated with tray dried product have been targeted for a comparative assessment.

Multi-Objective Optimization and Quality Evaluation of Short- and Medium-Wave Infrared Radiation Dried Carrot Slices

Optimum technology and quality evaluation of short- and medium-wave infrared radiation (SMIR) dried carrot slices were studied. Effects of drying temperature, drying time and infrared power of SMIR drying on the moisture content, color parameter and β-carotene content of dehydrated carrot slices were investigated. The experimental data were well predicted by a modified second-order polynomial model. Drying temperature and drying time had significant effects on moisture content, color parameter and β-carotene content. However, infrared power only showed significant effect on the moisture content. Response surface method (RSM) was used for optimization of SMIR drying of carrot slices, and the optimum condition was found as drying time of 50 min, infrared power of 1125 W, and drying temperature of 70 °C. SMIR dried products were proved to be favorable by comparing with hot-air dried ones due to its higher rehydration ratio (6.89) and β-carotene content (462.48 μg/g).

Drying Kinetics and Activation Energy of Asparagus Root (Asparagus racemosus Wild.) for Different Methods of Drying

Drying reduces the water activity of food product and hence increases the shelf life of the food. In the present study, fresh asparagus roots were pretreated in hot water at 80oC for 5 min. The methods of drying used for the study were tray drying, solar drying, vacuum drying and fluidized bed drying at four temperature levels 40, 50, 60 and 70oC. The complete drying of asparagus follow falling rate period only. The total time for drying decreases with increase in temperature of drying air from 40oC – 70oC. Fluidized bed dryer has a highest average drying rate as compare to tray dryer, solar dryer and vacuum dryer. Four empirical models, namely Page’s, Exponential, Generalized exponential and Logarithmic model were fitted in the drying data to describe the phenomena of drying process using a linearized regression technique. It was found that the Page’s model was best as it describe most precisely about the drying behavior of asparagus roots. The effective moisture diffusivity of asparagus roots varies from 7.14 × 10-9 to 3.70 × 10-8 m2/s and it was also found that diffusivity increases with increase in temperature. The activation energy was found to be from 11.797 to 30.318 kJ/mol.

Effects of boiling and in vitro gastrointestinal digestion on the antioxidant activity of Sonchus oleraceus leaves

Leaves of Sonchus oleraceus L. are especially rich in phenolic compounds and have potent extractable antioxidants. However, it is not known how their antioxidant activity changes after cooking and gastrointestinal digestion. We recorded the profile of phenolics and their associated antioxidant activity in both raw and boiled S. oleraceus leaf extracts after in vitro gastric and intestinal digestion, and quantified their antioxidant potentials using Caco-2 and HepG2 cells. Boiling significantly diminished the oxygen radical absorbance capacity (ORAC) and concentrations of ascorbate and chicoric acid in the soluble fractions. In contrast, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and concentrations of caftaric and chlorogenic acids were unaffected. Phenolics in the soluble fraction were absorbed into cultured human cells and exerted antioxidant activity. Only chlorogenic acid content remained stable during gastrointestinal digestion. S. oleraceus appears to be an excellent dietary source of phenolic antioxidants.

Steeping preservation of cauliflower with hurdle concept

Cauliflower is a rich source of proteins, carbohydrates, vitamins and minerals and also a very important vegetable having maximum availability in tropical climate from November to February which causes glut in the market and consequently producers do not get remunerative prices. The partially blanched cauliflower pieces of 3-4 cm long having stalk upto 2 cm in length are steeped in different levels of sodium chloride (NaCl, 2-6 %) and acetic acid (1-2 %) along with 350 ppm sulphur dioxide (SO2) using modified response surface methodology (RSM). The cauliflower samples steeped in 4 % NaCl, 1 % acetic acid and 350 ppm SO2 were rated best with maximum mean overall acceptability (OAA) score (6.90) and minimum mean preference (6.25) to the experimental run consisting of 6 % NaCl, 2 % acetic acid and 350 ppm SO2 was noted after 120 days of storage. There has been sharp decrease in pH values after 15 days of storage in all the experimental run of preserved cauliflower samples. The maximum mean decrease in hardness values (15.20-0.55 g.cm) was obtained in steeped cauliflower samples consisting of 6 % NaCl, 2 % acetic acid and 350 ppm SO2 during storage for 120 days at room temperature. The decrease in extent of browning, ascorbic acid and total carotenoids content in cauliflower samples was reported in all the experimental runs during 120 days of storage at room temperature. The optimum concentration for maximum desirability in the preservation of cauliflower consisted of 3.5 % sodium chloride and 1.1 % acetic acid and 350 ppm SO2.

Stability of vitamin C in fresh and freeze-dried capsicum stored at different temperatures

The objective of this study was to determine vitamin C stability in fresh and freeze-dried capsicum during storage at different temperatures. Fresh capsicum stored at 20 °C showed an initial decrease in vitamin C with a minimum peak after 2 days and then increased to a maximum peak after 13 days followed by a gradual decay. In general a gradual decrease of vitamin C was observed in the cases of fresh (i.e. stored at 5, -20, -40 °C) and freeze-dried capsicum stored at all temperatures (i.e. 60 to -40 °C). The degradation kinetics of vitamin C was modeled by zero and first order reaction and rate constants were estimated. The rate constant increased with the increase in storage temperature, while it was decreased with the decrease of moisture content. At storage temperature 5 °C, first order rate constants were observed as 7.1 × 10(-2), 7.7 × 10(-2), and 4.3 × 10(-3) day(-1) in the cases of samples containing moisture contents 94, 15 and 5 g/100 g sample, respectively.