Screening Potato Cultivars for Sugar Accumulation in Response to Cold Storage and Their Mitigation Through Reconditioning

Abstract

Potato processing industry is rising globally and increasing fast food demand of consumers exerts pressure on researchers to identify suitable potato cultivars for processing into chips and fries. Low sugar contents and light frying color are the principal traits to be observed for good chipping performance of potatoes. In potato industry, determination of sugar contents is particularly important as presence of high levels of sugars causes non enzymatic browning or Maillard reaction after frying of potato chips at high temperature. The current study was designed to screen out and assess the chipping potential of indigenous potato cultivars namely, Lady Rosetta, Santé. Hermes, Crozo, Kuroda and Asterix for sugar accumulation during storage at 3, 7 and 11ºC for 160 days (Phase I). The second phase was aimed to estimate the sugar reversion by applying reconditioning treatment at higher temperatures of 15, 20 and 25ºC for a short period of 30 days. All the physicochemical (specific gravity, dry matter, total starch ascorbic acid, sprouting, weight loss, hardness/firmness,) and biochemical analyses such as sugar contents (glucose, fructose, sucrose) and invertase enzyme activity were carried out at a regular interval of storage days. High Performance Liquid Chromatography (HPLC) was adopted for the quantification of sugars whereas the associated invertase activity appraised by spectrophotometrically. Considering the result of first phase; the correlation matrix for physicochemical and biochemical analyses revealed that specific gravity, dry matter content, percent weight loss and sprouting rate were positively correlated to sugar contents and invertase activity while negatively correlated to total starch, ascorbic acid and tuber’s hardness/firmness. Over the storage, gradual increase in sugar contents was observed during phase I, in which the maximum sugar accumulation was exhibited by tubers stored at 3ºC in contrast to 7 and 11ºC. Cold induced sweetening (CIS) under the influence of invertase activity was recorded highest in cultivar Kuroda, following the Santé, Asterix, Crozo, Hermes and Lady Rosetta. High temperature exposure to the stored tubers or reconditioning treatment for short time (Phase II) resulted in reversion of accumulated sugars to starch. The maximum reversion of sugars was attained at 20ºC as compared to 15 and 25ºC after 30th day of reconditioning. All the cultivars showed significant results for glucose, fructose and sucrose contents after reconditioning treatment such as Lady Rosetta (43.23, 38.33, 49.21 mg/100g), Hermes (48.97, 43.23, 39.23 mg/100g), Crozo (51.94, 46.72, 41.74 mg/100g), Santé (54.41, 51.37, 83.31mg/100g), Asterix (59.53, 62.11, 47.52 mg/100g) and Kuroda (86.93, 81.96, 51.21 mg/100g), respectively. The pattern of chips color was assessed and scored by using nine-point Hedonic scale after both phases. Consequently, significant variability (P < 0.05) in sugar contents and frying color was found among all cultivars, whereas Lady Rosetta with golden yellow chips color, Hermes having slightly yellow color and Crozo with yellow color were the most suitable cultivars for chips preparation after reconditioning. The outcomes of current study indicated that reconditioning at higher temperatures for short time resulted in a strong and diverse effect on starch sugar interconversion during storage. More importantly, these results proposed that reconditioning treatment of stored tubers could reduce CIS depending on the nature and type of the cultivar along with the applied storage conditions.