This study evaluated the effects of pretreatments (blanching (60 and 95 °C) and boiling) and drying methods (freeze-drying and oven drying) on the quality characteristics of potato flour derived from three potato varieties, namely, Shangi, Unica, and Dutch Robjin. The percentage flour yield, color, particle size distribution, flow characteristics, microstructural and functional properties of the potato flour were determined. Unica recorded the least peeling loss, while the Dutch Robjin variety had the highest. Color parameters were significantly affected (p < 0.05) by the pretreatments and drying methods. Freeze drying produced lighter potato flour (L* = 92.86) compared to the other methods. Boiling and blanching at 95 °C followed by oven drying recorded a low angle of repose and compressibility index, indicating better flow characteristics. The smallest particle size (56.5 µm) was recorded for the freeze-drying treatment, while boiling followed by oven drying had the largest particle size (307.5 µm). Microstructural results indicate that boiling and blanching at 95 °C, followed by oven drying resulted in damaged starch granules, while freeze-drying and low-temperature blanching (60 °C) maintained the native starch granule. Particle size and the solubility index of potato flour showed strong positive correlation. This study revealed that the pretreatments and drying methods affected potato flour’s physical and microstructural parameters differently, resulting in changes in their functionality.

Long-term use of fresh potatoes is constrained due to post-harvest losses and limited or poor storage systems. Loss of potato quality during storage is mostly due to weight loss, excessive sprouting, decaying, greening, pest attack and changes in sugar content which is a major concern for processors. The storability of three potato varieties namely Shangi, Unica, and Dutch Robijn was evaluated under four storage conditions: (1) room temperature (RT) (21.7 ± 5 °C) and ambient relative humidity (RH) (73.5 ± 6.7%); (2) 10 °C/75% RH; (3) 10 °C/ambient RH and (4) 7 °C/75% RH for 3 months. Parameters analysed included weight loss, sprouting, greening, rotting incidence and changes in simple sugars (sucrose, glucose and fructose) content. Shangi variety had the poorest storability having exhibited the highest weight loss, sprouting, greening and rotting rates among the varieties and in all storage conditions. In all the varieties, weight loss was highest at room temperature/RH (6.9–35.13%) and lowest at 7 °C/75% RH (1.6–3.7%). Sprouting rate was highest at RT/RH (100%) and lowest at 7 °C/75% RH (2.0–45.2%). Greening incidence was highest at RT/RH (10.3–24.0%) and lowest at 7 °C/75% RH (2.0–16.1%). The tubers accumulated simple sugars during storage with the highest relative accumulation recorded at 7 °C/75% RH. Total reducing sugars increased by 3.8–9.3-fold at RT/RH to 26.0–68.5-fold at 7 °C/75% RH. Low-temperature storage minimized the rate of physical tuber deterioration with 7 °C/75% RH best preserving the potatoes’ physical properties while it led to the highest accumulation of simple sugars.

Potatoes have attracted great interest as a feasible solution to food insecurity and climate change in Kenya. Many varieties have been developed but their nutritional value and suitability for domestic and industrial use are not sufficiently studied. A comparative study of physical attributes (tuber weight, size, shape, eye depth and number, specific gravity, colour) and nutrient composition (proximate, minerals, vitamins, and simple sugars) of three varieties (Unica, Shangi and Dutch robjin) were evaluated using standard methods. Shangi and Unica had lengths above 50 mm recommended for French fry processing, but had deep eyes (1.54-2.98 mm). Unica had a red skin colour while Shangi was yellow. Both varieties had yellow coloured flesh. The specific gravity of the varieties ranged from 1.08-1.12. Shangi and Unica were suitable for processing based on their physical attributes except for eye-depths. Dutch robjin had the highest content of protein (1.76%), carbohydrates (20.43%), total ash (1.10%), crude fibre (1.11%), iron (0.87 mg/100 g), thiamine (0.036 mg/100 g), niacin (0.93 mg/100 g), pyridoxine (1.92 mg/100 g) and folic acid (34.62 µg/100 g). Unica had the highest zinc (0.41 mg/100 g) and calcium (8.51 mg/100 g) contents. Reducing sugar content across the three varieties was within recommended range for processing (97.75-107.53 mg/100 g). There was a significant (p<0.05) varietal difference in most of the nutrient components. Dutch Robjin showed the best nutritional quality.