Drying and Quality Characteristics of Pretreated Guava (Psidium Guajava) Slices

Guava (Psidium guajava Linn.) is a sweet and highly nutritious fruits, which is high in minerals and vitamins especially vitamin C , needs preserved immediately after harvest. Drying has been one of the effective methods of preserving fruits and vegetables by reduction in moisture present to a level at which biochemical activities are hindered. Osmotic pretreatment reduces initial moisture and enhance retention of nutrients and physico-chemical qualities of the products. This research was therefore designed to study drying and quality characteristics of p.guajava. The slices were spitted in three parts, two parts pretreated separately in sucrose and maltodextrin solutions (1:10 w/v) for 1 h while control was untreated. All the pretreatment slices. Rehydration ratio (RR), effective moisture diffusivity (Deff) and activation energy (Ea) were determined. Quality parameters such as ascorbic acid, lycopene, calcium, potassium, tannin, colour, water absorption capacity, bulk density (BD) and tapped density (TD) were determined using standard procedures. Three criteria namely: coefficient of determination (R2),chi-square(χ2) values and Root Mean Square Error (RMSE) were used to select the best among the chosen models using SPSS version 25. Rehydration ratio (RR) values ranged from (2.31-2.51), (2.35-2.54), and (2.14-2.38) for sucrose, maltodextrin pretreated and control samples respectively. The Deff values of sucrose, maltodextrin pretreated and control p.guajava samples at 50, 60 and 70 oC ranged from(1.19 ×10-9 - 3.141× 10-9m2/s). The activation energies of the samples were 22.53, 29.88 and 49.83 kJ/mol. K for sucrose; Maltodextrin pretreated and control samples respectively. . The Modified Henderson and Pabis model was found to be best fit for the slices due to highest values of R2 ,lowest χ2 and RMSE values being 0.999,9.31E-05,0.0014737 and -0.00246 correspondinly for sucrose ,maltodextrin and control respectively at all temperatures. The values of water absorption capacity (WAC), bulk density (BD) rehydration ratio (RR) and tapped density (TD) ranged from (183-184), for sucrose pretreated samples, ranged (126 - 129 ) for maltodextrin pretreated samples (184-180) for control, bulk density ranged from (0.98-0.89), (0.77-0.82),( 0.68-0.79) for sucrose, maltodexrin pretreated and control sample respectively. RR values ranged from( 2.31-2.51), (2.35-2.54), and (2.14-2.38) for sucrose, maltodextrin pretreated and control samples respectively.TD ranged from (0.57-0.67), (0.53-0.64) and (0.52-0.62) for sucrose, maltodextrin pretreated and control samples respectively. The values of colour change (∆E), decreases as drying time increases, the values of L*, a*, and b* for the samples were 56.04, 52.01 and 51.34, respectively. This research showed that drying at 70 oC retained the nutritional attributes of the samples evaluated. The Modified Henderson and Pabis gave the best model that best fits the drying process, while sucrose pretreated samples minimized nutrient loss. Thus, adoption of this method could help local farmers and food processor produce quality and shelf-stable products.