The Effect of Drying Methods (Catalytic Flameless Infrared - Cfir, Oven and Solar Drying) On the Quality of Sweetpotato Flour

Conventional drying methods have many drawbacks that tend to reduce productivity. Infrared drying is one of the advance methods of drying technology that has higher drying rates and energy efficiency than most conventional methods. Catalytic flameless infrared (CFIR) drying is a new infrared drying technology that is being introduced into the food industry. In this work, the CFIR drying method was compared to solar and oven drying method to determine their effect on the proximate, physicochemical and pasting properties of sweetpotato (cv. Santom Pona) flour. Proximate compositions on six cultivars (Santom Pona, Apomuden, 199062.1, Faara, Cemsa 74-228 and Mohc) of sweetpotatoes were first determined. Since CFIR is a new technology in Ghana, drying conditions (drying temperature and time) were first investigated to help use the equipment. Proximate compositions on the six cultivars showed that moisture content ranged from 59.46±1.49 for Santom Pona to 84.71±2.93 in Apomuden. Ash content was highest in Mohc (4.88±1.52) and lowest in Santom Pona. Fibre content was also highest in Mohc (2.81±0.01) and lowest in Faara (0.90±0.00). Apomuden recorded the highest fat content (1.71±0.35) with Santom Pona recording the lowest (0.42±0.04). Protein content ranged from 1.27±0.62 (Mohc) to 4.22±0.33 (Apomuden). It was also observed that, drying temperature of 65°C and drying time of 120min produced good flour quality in terms of pasting profile. Comparing the three different drying methods, it was observed that, CFIR drying method produced flour with highest fat content (1.89±0.61), amylose content (37.87±0.00) and together with oven drying method, produced the highest bulk density. From the work, ash content ranged from 1.11±0.36% to 3.15±0.28%, fibre content ranged from 0.52±0.00% to 0.87±0.00%, protein content ranged from 1.12±0.36% to 3.15±0.94%, phosphorus content also ranged from 154.00±0.00mg/100g to 170.50±0.00mg/100g. Amylose content was observed to be between 23.09±0.00% (Solar drying) and 37.87±0.00% (CFIR drying). pH was least in CFIR (6.03) and highest in solar drying (6.23). Water solubility ranged from 20.31±0.15 to 27.87±0.90 whiles swelling power also ranged from 3.40±0.02 to 3.66±0.02 with CFIR recording the least. Bulk density was between 0.69±0.01g/ml and 0.81±0.04g/ml. For pasting properties, setback viscosity ranged from 25.50±2.12BU to 39±1.41BU, final viscosity ranged from 80.50±3.53 to 153.00±2.83BU with CFIR having the highest and solar drying having the least in both cases. Breakdown viscosity also ranged from 1.00±0.00 to 16.00±0.00BU, peak viscosity ranged from 62.50±0.71 to 138.50±2.12BU. CFIR also recorded the highest L* value for colour. This study has shown that, in drying sweetpotatoes (cv. Santom Pona), drying method is very essential because, it has effect on the final flour quality. CFIR, being a new technology, has also been shown to produce flour of high physicochemical and pasting quality. Therefore, in setting up a flour or starch factory, CFIR could be an alternative drying system.

Source: KNUST