Development and effectiveness of greenhouse type solar dryer for coriander leaves

Aim: Sun drying system is not able to provide the best drying performance and quality dried produce of leafy vegetables. To facilitate better options to the farmers, this study aims to develop and evaluate a cost-effective greenhouse type solar dryer to improve shelf stability of coriander leaves. Methodology: A greenhouse type solar dryer (5m x 3m x 2.3m) was developed with the provision of rigid frame, 200 µ UV stabilized LDPE glazing material, solar collector cum drying chamber, inlet air and outlet air openings. The dryer was evaluated for its performance, drying characteristics of coriander leaves and qualitative evaluation of dried product as compared to open sun drying. Results: The greenhouse type solar dryer performed well for coriander drying with increased level of temperature inside the dryer (42oC) and 24% reduced drying time as compared to sun drying (29oC).The loading capacity, efficiency, payback period and B:C ratio of the dryer were found to be 100 kg, 70.47 %, 1.26 yr and 1.79, respectively. The drying of coriander leaves occured mostly in falling rate period. Coriander leaves dried under the dryer possessed higher values of chlorophyll content (1.356 mg g-1 of tissue), ascorbic acid content (111.257 mg 100g-1), rehydration ratio (5.302) and coefficient of rehydration (0.762) than sun dried coriander leaves with the respective values of these quality parameters being 1.097 mg g-1 of tissue, 62.37 mg 100g-1, 4.715 and 0.689, respectively.

Evaluation Data of Dried Vegetables and Fruits

Drying is the process of removing of the water that has destroying effect in food products by evaporation and. Research project on the basis of direct sun drying and solar greenhouse. Basic operations research in food engineering, food chemistry, food quality control and toxicology has been established over such a broad spectrum. Subjects of investigation were in accordance with all of the values of dry matter basis. The study of dry matter and water activity values of each product (aw), direct sun drying, drying in the greenhouse. It was determined comparing nutrients of samples those were applied directly to the greenhouse and drying in the sun. Sampling patterns of research were explained as follow; tomatoes drying in the sun (external environment), and greenhouse, bell peppers in the greenhouse and drying in the sun, soaked raisins (sultanas) and not-soaked (raisin), sun-dried, sun-dried fig products directly. Nutrients of the samples such as; lycopene, thiamine (B1), riboflavin (B2), retinol (A), Pyridoxine (B6), ascorbic acid (C), folic acid, magnesium (Mg), potassium (K), sodium (Na), phosphorus (P), zinc (Zn), iron (Fe), copper (Cu) were quantitatively determined. The red pepper products, dried figs and dried grapes mycotoxin amounts were in safe levels, which had not created any hazard and risk for health. Red pepper and dried figs, total aflatoxins, (B1, B2, G1, G2), ochratoxin A (OTA) levels in raisin in the European Union is set well below the limits in terms of human health hazard and the risk factor has been identified.

Thermal Analysis of Tilapia Fish Drying by Hybrid Solar Thermal Drying System

The present work presents a hybrid solar thermal drying of Tilapia fish to improve the product quality and satisfy the importers. The developed hybrid dryer utilized direct solar drying, a solar air heater and a thermal backup unit which sustains the drying process during the night, cloudy and rainy weather conditions. Besides, a new feature of the developed dryer utilizes the flue gas exhausted from the thermal unit to enhance the updraft in the drying chamber by re-injection of the flue gases in the chimney. The initial moisture content of the Tilapia fish used in the investigation was 246.6% on a dry basis, equivalent to 74% on a wet basis. The investigations were repeated three times on different days. Experimental results showed that the moisture content was reduced to an average final of 17.0% db (5.0% wb) within 17.5 hours, while in the open sun drying, it required around 48-72 hours. Hybrid solar drying required around 72% shorter time than open sun drying. The average overall drying efficiency of the developed system for drying Tilapia fish was 13.0%. The Re-injection technique used in the present hybrid solar-thermal system has excluded the need for an electric source for air extraction from the drying chamber, which is highly desired in the rural and fishery regions.

Impact of Different Drying Techniques on Quality Traits of Ginger (Zingiber officinale Rosc.) Rhizomes

Under the present investigation, ginger was produced at the instruction cum research plots of the Department of Plantation Crops and Processing, Faculty of Horticulture, Uttar Banga Krishi Viswavidyalaya, Pundibari, Cooch Behar, West Bengal. The experiment was laid out in a factorial CRD. The study was undertaken with four ginger varieties namely Gorubathan, Suprabha, Suruchi and Suravi to evaluate the effect of different drying methods (sun drying, hot air drying at 50OC, 60oC and 70oC and microwave drying on time required for drying to a moisture content of 8 – 10% and to chemical composition (essential oil, oleoresin content and crude fiber content) of the end product. Results shown that Gorubathan variety has the highest essential oil (2.243%) and oleoresin content (14.840%) among the four varieties in this study, highest crude fiber content (5.253%) was observed in Suprabha and highest dry recovery (25.77%) was obtained from Suravi variety. In hot air drying, with increase in temperature essential oil, oleoresin and crude fiber content in dry ginger as well as dry recovery reduced. With high dry recovery (25.77%), essential oil (2.037%) and oleoresin content (13.510%) and moderately low crude fiber content (4.637%), it can be concluded that Suravi variety is best suitable for producing dry ginger. Apart from microwave drying, sun drying can be recommended as better practice, when hygienically conducted, based on essential oil and oleoresin content.

Drying characteristics and prediction of best fitted drying model for coriander leaves

Drying experiments were conducted on coriander leaves as affected by drying methods (solar greenhouse drying and open sun drying), pretreatments (dipping in a solution of magnesium chloride + sodium bicarbonate + potassium metabisulphite, boiled water blanching containing sodium metabisulphite, and untreated), and loading densities (2.0, 2.5 and 3.0 kg/m2). Validity of three commonly used drying models were examined to predict the most suitable drying model for coriander leaves. The increased drying temperature under solar greenhouse dryer (42°C) increases the amount of moisture removal from the coriander leaves and reduces the drying time by increasing the drying rate as compared to open sun drying (29°C), at all the selected levels of pretreatments and loading densities. Chemically treated coriander leaves dehydrated under a solar greenhouse dryer required less drying time than other treated leaves and dried leaves. Nevertheless, drying methods and loading densities had significant effects, while treatment effects were marginal. It was found that reduction of moisture and moisture removal rate per unit time occurred mostly in the falling rate period except some accelerated removal of moisture at the beginning up to 150 minutes. Page's model was found most appropriate for drying coriander leaves among the selected models.

Effects of sun-drying on the antioxidant potentials of pepper (Capsicum) varieties

The present study investigated the effects of sun-drying on the antioxidant potential of three pepper varieties: Capsicum annuum var, Capsicum chinense and Capsicum annuum. Fresh fruits of the pepper varieties were collected, washed under distilled water and were divided into two parts: one for fresh sample and the other for the dried sample. Dried and fresh samples of the pepper varieties were homogenized and extracted with methanol. The concentrations of total phenolics and flavonoids were evaluated; DPPH-radical scavenging activity and the FRAP potential of the extracts were also determined. The results revealed that sun-drying process significantly reduced the total phenolic content of C. annuum var, C. chinense and C. annuum from 5.91 ± 0.22 mg/g GAE, 6.9 ± 0.23 mg/g GAE, 6.67 ± 0.99 mg/g GAE to 3.31 ± 0.72 mg/g GAE, 3.59 ± 0.89 mg/g GAE, 3.01 ± 0.17 mg/g GAE respectively and flavonoid content from 3.80 ± 0.02 mg/g QE, 3.91 + 0.08 mg/g QE, 3.84 ± 0.08 mg/g QE to 1.26 ± 0.90 mg/g QE, 1.95 ± 0.07 mg/g QE, 1.23 ± 0.04 mg/g QE respectively. The result also revealed that the fresh samples of C. annuum var, C. chinense and C. annuum exhibited higher percentage inhibition of DPPH-radical at 59.4 ± 0.5%, 61.2 ± 0.6%, 58.9 ± 0.2% respectively and were significantly different from the percentage inhibition by the dried samples: 39.2 ± 0.5%, 42.4 ± 0.4%, 38.6 ± 0.6% respectively.The FRAP potential of the fresh samples of C. annuum var, C. chinense and C. annuum: 588.56 ± 29.4 ìmol Fe(II)/g, 691.34 ± 20.46 ìmol Fe(II)/g and 598.9 ± 23. 82 ìmol Fe(II)/g respectively were significantly different from the dried samples: 370.22 ± 14.75 ìmol Fe(II)/g, 392.34 ± 45.74 ìmol Fe(II)/g and 358.6 ± 30.08 ìmol Fe(II)/g respectively. The three Capsicum species are very rich in antioxidants. However, the sun drying method reduced the antioxidant capacities of the peppers, thus further studies should be carried out on the best method for the preservation of Capsicum species. Key Words: Capsicum. annuum var, C. chinense, C. annuum, Antioxidant, Sun-drying, methanolic extract

Effect of Heat Treatment on Rumen Degradability of Gliricia sepium leaves

An experiment with the objective to investigate the effect of different temperature regimes during heat treatment of Gliricidia sepium leaves was conducted following a completely randomized design with 4 treatments and 3 replications. Gliricidia leaves were exposed to three temperature regimes namely oven heating at 60oC (T60), 90oC (T90), and 120oC (T120) respectively and followed by sun-drying compared to sun drying as control (Con). The dry matter and protein degradation were measured using In Sacco method in three fistulated Bali cows fed a standard diet. Protein solubility (a) and the insoluble but potentially degradable fraction (b) were linearly reduced (P<0,001) by the increased temperature in the oven as compared to sun drying. The degradation rate (c) of protein in the rumen was increased at all heating treatments. The effective dry matter and protein degradation of gliricidia leaf was significantly (P<0,01) reduced by heat treatment in T90 and no further reduction in T120. The solubility fraction of DM was significantly reduced (P<0.05) when heated in the oven at 120oC, meanwhile the b value for DM linearly decline with the increasing heating temperature. Heating also increased the lag time required for the degradation to commence. It, therefore, can be concluded that oven drying at 90oC is a simple effective means to reduce ruminal protein degradation of gliricidia leaves.