The influence of drying on the physical properties of sweet potato slices

The effects of varying drying conditions on the physical properties of sweet potato slices were studied. Fresh tubers were peeled, washed and cut into two shapes (rectangular: 50 x 60 mm and cylindrical 60 mm diameter) of two thicknesses (4 and 6 mm) slices. Some slices were blanched in water at 90oC for 5 mins and some unblanched. Both were either sun dried or oven dried at various temperatures; 50 oC , 70 oC and 90 oC. The bulk density, dimensional changes and moisture loss were investigated. The results shown that, moisture loss and percent shrinkage increased with increased in temperature. Sweet potato of 4 mm thick samples lost more moisture with higher % shrinkage than 6 mm thick samples, although not significantly (P>0.05). Logarithmic equations gave best fit of moisture loss with time at the different temperatures. Generally, in all the samples, thickness had a greater influence on % shrinkage than shape. Blanching minimized %shrinkage although not significantly (P>0.05). Greater shrinkage took place in the sample thickness (up to 63%) than across product diameter or thickness (values up to 26.3%). % shrinkage can be predicted using either the linear or logarithmic equations. The bulk densities of dried sweet potato slices were not influenced by blanching

Bread-slicing machine

This study developed a compact front loading machine for slicing loaves of bread.  The machine is fast, efficient, safe and easy to operate.  It was designed to accommodate a normal loaf of bread per pass.  It works on the principle of gravity loaf in-feed system and the up-and-down reciprocating motion of the blade frame that carries 22 parallel cutting blades spaced at a regular interval of 14.5 mm apart.  It is driven by a 2 horsepower electric motor via a V-belt power transmission system.  The moving components are born on self-lubricating bearings and specially designed vibration absorbers; it automatically stops to save running cost once the loaf is completely sliced.  It also incorporates a crumb collection tray to enhance the hygiene of the process. Evaluation tests revealed that increasing the cutting speed above the standard commercial bakery speed of 420 r/min increased bread wastage and reduced uniformity of slice thickness

Some quality properties of yellow-fleshed sweet potato flour as affected by different drying methods

Abstract This study compared some quality properties of yellow-fleshed sweet potato flour samples as affected by pretreatments (0.02% sulfite; blanching 85 °C for 3 min 30 s and steam blanching 100 °C for 2 min) and drying methods (oven, sun, and drum drying). The physicochemical composition, functional properties, pasting profile, and least gelation concentration of the flours were determined. Before pretreatment, the sweet potato tubers were sorted, weighed, rinsed, peeled, and diced. The smallest particle size (58 μm) was recorded for samples blanched at 85 °C followed by oven drying while drum-dried samples had the largest particle size (119.5 μm). The pH values (5.58 - 5.90) of the pretreated sun- and oven-dried samples were significantly (p<0.05) impacted by 0.02% sulfite. Compared to other drying methods. drum-dried samples had low bulk density (0.36 g/ml), the highest water (531%) and oil absorption capacities (168.5%,) and the least dispersibility (35%). Drum-dried samples had the highest swelling capacities at 60 – 80 °C but the values decreased at 80 – 90 °C compared to samples from other drying methods that had low swelling capacity at 60 - 70 °C but the values increased as the temperature increased from 70 – 90 °C. Results of the sample pasting profiles showed that pretreatment and drying techniques were significant on the various viscosities measured. Drum-dried samples had the lowest trough viscosity (18.13 RVU), final viscosity (24.88 RVU), setback viscosity (6.75 RVU), peak time (1.07 min), and pasting temperature (0 °C). This study concluded that the pretreatment and drying methods affected the quality properties of the yellow-fleshed sweet potato flour samples differently, consequently altering their functionality. Graphical Abstrac