Effect of Storage Method on the Nutritional Composition and Sensory Acceptability of Potato in Holeta, Ethiopia

Moisture Content

Five gram of ground sample in a clean dry moisture crucible were placed in oven at 105oc for three hour and the sample were allowed to cool in a desiccators to maintain the sample temperature to room temperature for 30 minute.

𝑀𝐶 = Weight before−Weight after ∗100 /Total weight

Total Protein–Kjeldhal Method

One gram ground sample measured and transferred into completely dry kjeldhal flask. Ten gram of kjeldhal Tablet was added to the sample inside the flask. Twenty milliliter of 98% concentrated sulphuric acid was mixed with the sample. The sample digestion was started by connecting the kjeldhal flasks with the digestion rock (2000 Food ALYT SBS). And the digestion was completed when the brown color of the sample was completely disappeared. After the digested sample was cooled, 250 ml of distilled water and 70 ml of sodium hydroxide (32%) were added and distilled into 25ml of excess boric acid containing 0.5ml of screened indicator. The distillate was titrated with 0.1N hydrochloric acid to the red end point.

𝑇𝑜𝑡𝑎𝑙 (%) = T−B ∗0.1401/ W, W is weight of the sample taken for analysis T is volume of HCl used for titration B is blank used as control Crude protein (CP%) = N*6.25

Fat Content

Three gram of dry sample was weighed to in an extraction thimble; it was placed in the extraction unit. The flask was connected to hexane containing at 2/3 of total volume to the extractor until 6 hours. When finished, the hexane was evaporated by distillation or in a Rota evaporator. The flasks were cooled in a dryer and weighed.

% oil = weight of sample–weight of residue after extraction x 100/Weight of sample

Ash Content

Three gram of dry sample was weighed out into the crucible, after the crucible has been heated and weighed and was placed in a temperature controlled furnace at 550oC for about 3hours for proper ashing. The crucible was then cooled in desiccators and immediately weighed.

% Ash = weight of ash remaining x 100/Weight of original sample

Physiological changes

The physiological change observed for five month storage period was presented in Table  1. Physiological changes in the stored potato were very low in the first month and in ground pit storage were very low. The physiological change such as shape, weight, color and germination were normal up to fourth month storage. For ground pit storage up to five month storage there were no physiological changes. But for the other storage methods there were physiological change. Dark house storage and infield storage were more physiological change was observed especially in weight loss and sprout. Ground pit storage method was superior in preserving the physiological change which keeps from sprouting and fresh more than in field and dark house storage methods. These findings were in agreement with reports by Sandifolo, et al. [7].

Nutrient Content Analysis Of Potato

The means of percent change in the various nutrients before and after the five month storage were observed. The ash content of potato among the five storage months there were significant different at p<0.05 (Table 2). While protein, Fat and Moisture content of potato for the five month storage there were not significant different at p<0.05 (Table 2). The ash content of protein increase from first month (5.2) up to the five month storage (6.2). among the storage methods the ash content of potato there were significant different at p<0.05.while protein, fat and moisture content there were not significant different at p<0.05.after five month the ash content were high value in ground pit storage(5.9%) and infield storage (6.02%) respectively. Generally results of chemical analysis of crude protein, fat, ash and moisture content shown in Tables 2 & 3 the storage methods differed significantly (p<0.05) in preserving the ash content. Protein, fat and moisture content were not differed significantly both on effect of storage methods and storage time (Tables 2 & 3). While the ash content was significantly (p<0.05) higher in all storage methods and storage time (Tables 2 & 3).

Acceptability of Stored Potato

For five month storage sensory data for crisp and boiled potato food products were evaluated .taste and color of the crisp evaluated for five month storage there were no significant different at p<0.05 (Table 4). While texture and overall acceptability of the crisp have a significant different at p<0.05 (Table 4). the overall acceptability during the first month were (4.5%) and it decrease after five month (3.5) Table 4 indicates after five month storage the acceptability of potato crisp decrease. for boiled potato for five month storage sensory data for taste, color ,texture and overall acceptability for the crisp were significant different at p<0.05 (Table 4). Among the storage methods color, taste, texture and overall acceptability there were no significant different at p<0.05 (Table 5). While taste, color and texture of the boiled potato there were no significant different at p<0.05 (Table 5). Generally Results of sensory evaluation shown in Tables 4 & 5. Texture and over all acceptability in fried and boiled form of potato significantly affect acceptability of potato in all storage methods. Taste and color in fried form of potato not significantly (p<0.05) affect acceptability of potato in storage methods and storage time (Tables 4 & 5). This finding in agreement with Mbeza, et al. [8]. In ground pit and dark house storage were more acceptable in fried and boiled form of potato shown in Tables 4 & 5. Dark house storage was preferable for the two potato products boiled and fried form (crisp) forms Tables 4 & 5. In terms of physiological and nutrient preservation of potato ground pit were preferable up to five month storage (Tables 1-3) [9, 10, 11].