Effect of osmotic dehydration pretreatments on drying rate and post-drying quality attributes of red bell pepper(capsicum annuum)

Bell pepper (capsicum annuum) is a common vegetable plant and the most popular world-wide and mildest member of capsicum family. It is very easy to cultivate but highly perishable because of its characteristic lower sugar and acidic contents. It lacks built-in protection mechanisms which makes it more vulnerable to deterioration and thus leading to rapid metabolic activities within its cells once harvested. As a result of the aforementioned, it usually experience high postharvest losses in its season and becomes scarce and of low standard at off-season. This work was done to study the factors affecting the drying process of pretreated red bell pepper; and also to investigate the effect of osmotic pretreatments(solution concentration, solution temperature and process duration) on the drying rate and quality attributes (vitamin C, vitamin A and ash content) of red bell pepper. A 43 factorial experiment in Randomized Complete Block Design (RCBD) was used. The factors taken into consideration were osmotic process duration (60 min-150 min), osmotic solution concentration 5% (w/w)-20% (w/w), and osmotic solution temperature (30°C-60°C), all at four levels and replicated three times. A drying temperature of 60˚C was used for all the pretreated samples inside a temperature-controlled fabricated dryer. Results revealed that not all the osmotic dehydration pretreatments showed significant effect on the drying rate at p≤0.05. Also, increase in osmotic dehydration pretreatment conditions did not cause the average values of vitamin C, vitamin A and ash content to fall below 120 mg/100g, 1.40 mg/100g and 8.0% respectively. Further studies should be carried out on the storability, shrinkage and rehydration properties of dried samples, and modeling and optimization of the process

Effects of Pre-Treatments and Drying Temperatures on Drying Rate and Quality of African Catfish (Clarias gariepinus)

Effects of pre-treatments and drying temperatures on the drying rate and the quality of African Catfish Clarias gariepinus was examined by drying samples of catfish under four different temperatures (40 0C, 45 0C, 50 0C and 55 0C) and four different pre-treatment methods (Salting, Sugaring, Blanching, and Control) using an experimental dryer. Drying of the fish samples for all the pre-treatments at 40 0C to 55 0C occurred in the falling rate period only showing that the predominant mechanism of mass transfer in drying process of catfish is that of internal mass transfer. The drying rate increases with increase in temperature for all the pre-treatment methods and decreases with time. The statistical analysis using a factorial design shows that drying rate was significant at (F; 0.05) but there is no significant difference in the pre-treatment methods as well as the interaction between drying temperature and the pre-treatment. The quality parameters (Protein, crude fat and Ash) measured decreases with increase in the drying temperature for all the samples with the blanched samples having the highest value of % protein of 55.94 at 45 0C. The sugared samples have the least value of 43.82% at 55 0C. The control has the highest amount of Ash 5.36% at 40 0C and 4.04% for blanched samples at 55 0C. Generally the values are higher for blanched samples and low for the sugar treated samples. Keywords: Temperature, pre-treatment, falling rate, drying rate, quality

Process of Modeling and Optimizing the Osmotic Dehydration Pre-treatment of Okra Drying

Okra [Abelmoschuscaillei (A. Chev.) Stevels] drying was studied by a factorial experiment under randomized complete block design using a laboratory-scale hot-air dryer. Two osmotic solution concentrations (40 and 60 oBrix of sucrose), three osmotic process durations (60, 120 and 180 min) and four drying temperatures (50, 60, 70 and 80 oC) were considered with each trial conducted in triplicates. Drying rate was determined as the ratio of change in mass of okra to the change in drying time as drying progresses. The ash content, crude fibre, crude fat, crude protein, bulk density, least gelation concentration and water absorption capacity were investigated as quality parameters. Model equations were developed using Essential Regression (ESSREG) analysis and Statistical Package for Social Sciences (SPSS) to relate output parameters to process variables. The results showed that an optimum drying rate of 16.69 g/h could be achieved by subjecting okra to osmotic dehydration pretreatment using a solution of 40 oBrix sucrose for 149.10 min and dried with a temperature of 80 oC. The ash content of 3.76% could be obtained at 40 oBrix, 180 min and 50 oC. An optimum value of 29.65% was obtained for crude fibre at an osmotic solution concentration of 60 °Brix, osmotic process duration of 180 min and drying temperature of 80 oC. Crude fat content of okra has 4.03% as its optimum value and this corresponds to a combination of 60 oBrix osmotic solution concentration, 180 min osmotic process duration and 74.60 oC drying temperature. An osmotic solution concentration of 60 °Brix, osmotic process duration of 60 min and drying temperature of 80 oC should be selected to give the optimum crude protein of 14.12%. Predicted values of drying rate, ash content, crude fibre, crude fat, crude protein and water absorption capacity (WAC) compared favourably with the observed values. This implies the models reliably predicted the drying characteristics of okra very well in terms of these output parameters. It could be inferred from this study that the drying process of okra can be optimized under different drying conditions. Further studies should be carried out on the factors that affect the storability of dried okra for long-time storage and preservation. An investigation into the use of sodium chloride for osmotic dehydration pretreatment as a means of improving the post-drying palatability of okra should be considered for further study

Process modelling and optimization of osmotic dehydration assisted drying of red bell peppper

Osmotic dehydration (pretreatment) of red bell pepper in hypertonic salt (NaCl) solution and drying was studied. A  4X4X4 factorial experiment in a Randomized Complete Block Design (RCBD) was used for the pretreatment and pretreated samples were later dried in a fabricated laboratory dryer. Process variables considered were four levels each of osmotic process durations (30, 60, 90 and 120 min), osmotic solution concentrations (5, 10, 15 and 20 % w/w of sodium chloride) and osmotic solution temperatures (30, 40, 50 and 600C) with each trial conducted in triplicates while a drying temperature of 600C was used throughout the experiment. Drying rate was estimated for all test runs while vitamin C, vitamin A, ash content, water loss and solid gain were estimated as quality parameters. Model equations were developed with Essential Regression (ESSREG) software package which related output parameters to process variables and validated. Results gave optimum drying rate (maximized), vitamin C (maximized), vitamin A (maximized), water loss (maximized), solid gain (maximized) and ash content (minimized) of 4.26 g/h, 152.82 mg/100g, 1.42 mg/100g, 0.24 g/g, 0.91 g/g and 8.04 % respectively.Keywords: osmotic dehydration, drying, optimizatio

ALMOND OIL: POWERHOUSE OF NUTRIENTS

The relative abundance of almond seed in several tropical regions of the world coupled with the little knowledge of its utilization in vegetable oil production prompted the need for this review. The aim is to review almond oil expression through different extraction/expression approach, the economic and health benefits of almond oil, and the challenges and prospects of almond oil extraction in Nigeria. This review covers the recent significant materials found in the literature on almond seed and oil extraction/expression. Almond oil is an essential oil packed with a lot of nutrients that are beneficial to human health. Therefore, it is important to devise better approach for maximum oil extraction/ expression