Effect of Pre-Treatment Methods on the Quality Attributes of Tomato Powder

Abstract

Pretreatment of tomatoes into powder reduces spoilage and postharvest loses; however, maintaining the nutritional quality of the powder poses a challenge. Thus, a quantitative approach was employed to measure the effect of some pretreatment methods of making tomato powder, where fresh tomatoes were blanched and exposed to different pre-drying treatments (untreated, treatment with 2% NaCl, 2% CaCl and 0.25% Na₂S₂O₂). These samples were then oven dried at 60^oC for 8 h before blending to the various powders. The proximate parameters (ash, fibre, protein, CHO, fats, moisture), physic chemical, antioxidants, colour and microbial parameter of the powder samples were then determined over a duration of 3 months. Results of the study showed that oven drying and chemical pretreatment significantly increased the nutrient component of the tomato powder and decreased cfu/g of bacteria, which could enhance the shelf life of the product. The antioxidants properties such as lycopene, B carotene, Vitamin C, and colour were significantly retained with chemical pretreatment. All pretreated samples retained more nutrients and reduced microbial load of tomato powder. That of Na₂S₂O₅ retained more nutrients while CaCl₂ retained more antioxidant properties. The NaCl treated powdered samples retained more ash and total fiber. Similar observations were made for antioxidants properties. L*a*b values of colour were higher at month 0 and lowest at month 3, this implies that at month 3, traces of undesired colour change began and as such, storage beyond this time may be unhealthy. Also, at month 0, Na₂S₂O₅ retained higher values of colour (L*a*b) whereas CaCl₂ retained more at month 3. There was a gradual increase in the bacteria and fungi load as the storage period increased. The pre-drying treatments adopted showed potentials to enhance the quality and shelf life of tomato powder although may not be encouraged beyond 3 months of storage.