Potato tuber sugar content during development and storage (10°C): possible predictors of storage potential and the role of sucrose in storage hexose accumulation

Summary Reducing sugar and sucrose contents of potato tubers (Solanum tuberosum L.) from six cultivars were monitored both during the growing season and after a four months storage period at 10°C. Significant correlations were found between tuber sugar contents (sucrose, reducing and total) measured at harvest and the reducing sugar content after storage. Similarly, in five of the six cultivars, the sucrose loss and the corresponding reducing sugar gain during storage were significantly correlated.     

Increase in phosphorylase activity during cold-induced sugar accumulation in potato tubers

Summary The accumulation of reducing sugars, sucrose and hexose phosphates in cv. Bintje and genotype KW77-2916 during storage at 2, 4, or 8°C was studied in relation to several catalytic activities. Bintje tubers accumulated sugars during storage at 2 or 4°C, whereas KW77-2916 showed reduced cold-sweetening at 2°C. The increase in glucose 6-phosphate and sucrose occurred concurrently and preceded the increase in reducing sugar concentration. Phosphorylase activity showed a strong interaction with temperature, storage duration and sugar accumulation in both genotypes. Invertase activity increased in Bintje concomitantly with the increase in reducing sugars, but this effect was less obvious in KW77-2916. The activities of other glycolytic and Krebs cycle enzymes showed no obvious correlation with sugar accumulation. It is suggested that the increase in phosphorylase activity acts as a triggering event in the sweetening of potato tubers during cold storage.     

Effects of nitrogen,phosphorus and potassium fertilizer treatments on weight loss and changes in chemical composition of potato tubers stored at 4°C

Summary Pot and field experiments were carried out to test fertilizer treatments on the behaviour of potato tubers stores at 4°C and ≥90% relative humidity for 6 months. Weight losses (separated into water and dry matter) were enhanced after N and K fertilization and decreased by increasing P supply. Glucose and fructose contents were reduced at harvest by high N-fertilizer rates compared to no or low fertilization, but throughout storage reducing sugar accumulation was increased, sucrose reduction was decreased and ascorbic acid was increased. K fertilization affected the chemical composition of the tubers somewhat similar to that of nitrogen fertilization. High initial nitrate content of the tubers seemed to be increased and low nitrate values were decreased during storage. The tubers from pot experiments showed similar changes but of greater magnitude.     

The immediate effect of gamma irradiation upon the sugar content of potatoes previously stored at 2, 4.5, 6, 10 and 15.5°C

Summary The sugar content of samples of potatoes, cv. Majestic, was varied by storage for 4 weeks at 2, 4.5, 6, 10 and 15.5°C, before irradiation with 10 krad. With initial sucrose contents of 0.14–0.37% FW (tubers from 4.5–15.5°C) the marked temporary increase in sucrose, as reported previously, was observed, reaching a maximum after 3–7 days before falling rapidly to a level rather higher than in non-irradiated tubers. Tubers from 2°C, with 1.4% sucrose, showed an immediate drop in this after irradiation, succeeded within 3 days by a rise to values not significantly different from the controls. Irradiation caused a significant increase in reducing sugar content, for a period of up to 7 days in sweetened tubers, but for 21 days or more in unsweetened tubers. Previous storage at the different temperatures had some permanent residual effect upon the sugar content of the controls during subsequent storage for up to 90 days at 10°C.     

The relationship between common scab severity and reducing sugar contents in the peel of potato tubers

Summary Total sugar, reducing sugar, glucose, fructose, and sucrose of scabbed (Streptomyces scabies) and scab-free harvested tubers of several potato cultivars were analysed in four portions (pell and tube flesh separtely, from basal and apical halves), and also in small whole growing tubers. The peel of scabby harvested tubes had higher reducing sugar (glucose and fructose) contents than that of corresponding scab-free tubers. The sugar contents in the flesh and in small growing tubers did not show significant difference beween the scabbed and scab-free state. Tubers of scab-susceptible cultivars had more scab and a higher reducing sugar content than those of resistant cultivars. The results indicate that the contents of reducing sugar (glucose and fructose) in tuber peel are positively correlated with scab severity.     

Accumulation of sugars in microtubers of potato node cuttings (cv. Kennebec) during cold storage

Summary Microtubers of potato cultivar Kennebec were stored for two months at 2 or 8°C and sampled at selected intervals for the determination of glucose, fructose, sucrose and sprout weight. The aim of this experiment was to determine whether these microtubers show the same response to storage temperature with respect to sweetening as field grown tubers. During storage at 2 °C, reducing sugars and sucrose increased rapidly to a concentration of over 1.0 and 0.7 g/100 g fresh weight, respectively. In contrast, in tubers kept at 8°C, only a relatively slight increase in reducing sugar concentration to 0.3 g/100 g fresh weight was observed and sucrose concentration remained virtually the same.     

An investigation of the level of reducing sugars in diploid potatoes before and after cold storage

Summary The reducing sugar content and chip colour were studied in diploid potatoes bred for superior table and chipping quality. The reducing sugar content in the tubers of 119 diploid clones was estimated before and after cold storage (4–6°C) in the years 1987–1991, and reducing sugar and chip colour were determined in 1990 and 1991 for 36 clones. Thirty two clones had a significantly lower reducing sugar content after cold storage than cv. Mila. The year of evaluation, storage temperature and genotype significantly affected the reducing sugar content.     

High temperature storage of potato (Solanum tuberosum L.) for processing — a feasibility study

Tubers of three potato cultivars were stored at room temperature (20–39°C, 30–75% RH), under an insulated storage run on passive evaporative cooling (16–30°C, 70–90% RH) and a refrigerated storage (2–4°C, 90–95% RH) for 14 weeks and studied periodically for storage losses, reducing sugar content and dry matter percent of tubers, in order to explore the possibility of storing potatoes for processing at higher temperatures. Physiological losses in tubers remained less than 10% until 12 weeks of storage under evaporatively cooled storage. Reducing sugar contents increased by only 52.4–242.1% in tubers stored in evaporatively cooled storage as compared to 90.5–484.2% increase in tubers stored in refrigerated storage until 14 weeks. Potatoes stored in evaporatively cooled store were more suitable for processing into chips and french fries due to lower physiological losses and lower reducing sugar content of tubers.     

Effects of short periods of chilling and warming on potato sugar content and chipping quality

Two days of chilling (exposure to 1 C) had no detectable effect on chip color or sugar content of potato (Solanum tuberosum L.) tubers. Four days of chilling led to increases in sugars if potatoes were stored at 10 C or 19 C for 3 to 4 days after chilling ended. Longer chilling gave increases in sugars by the end of the chilling period, and returning tubers to 10 C or 19 C magnified the response. Glucose and fructose gave similar increases from chilling treatments, except that glucose levels were consistently greater. Sucrose was increased by chilling, but the response pattern did not always resemble that of the reducing sugars. Twenty-seven days of storage at 19 C after chilling lowered levels of reducing sugars late in the storage season but not in December. Cultivars differed in response to chilling. Kennebec tubers accumulated far more reducing sugars but much less sucrose than did Norchip tubers. Storage at 19 C after chilling lowered the sucrose content of Kennebec and Monona while raising that of Norchip.     

Small tuber studies of sugar accumulation in potatoes

Small potato tubers, less than 1 cm in diameter, responded in a manner typical of larger tubers and accumulated sucrose and reducing sugars during storage at 1°C. Prolonged soaking (50% submerged) was used as a method for introducing metabolic inhibitors into intact, small tubers. Judging from the effects on respiration, cycloheximide was absorbed within 25 h. Cycloheximide treatment inhibited the sucrose and reducing sugar accumulation associated with storage at 1°C     

Sugar-end in Russet Burbank potatoes

Tissue selected from the stem- and bud-end of reconditioned tubers having sugar-end disorder was compared by color after frying and chemical composition to tissue removed from the two ends of tubers without sugar-end disorder taken directly from cold storage at 45 F, and after reconditioning 3 weeks at 70 F. Chemical analyses of selected tissue suggested that the dark finish-fry color at the stem-end of sugar-end tubers following reconditioning at 70 F was due to the inability of the physiological systems within the tissue to convert reducing sugars to starch and/or to use these sugars in the respiratory process. Of the components analyzed, only a high reducing sugar content was associated with a dark finish-fry color. Neither sucrose nor free amino acid content was associated with the sugar-end disorder. Extending the reconditioning period at 70 F for sugar-end tubers did not lower the reducing sugar content or the darkening of the stem-end tissue on frying.     

马铃薯贮藏还原糖含量与不同因素的相互关系的分析

马铃薯贮藏过程中其还原据含量受温度、体积、时间以及通风量和光照条件的影响。用夏·薛·哈(Somogyi—Shaffer—Hartmarin)三氏法测定了8541至8545、东北白和紫花白7品种(系)的马铃薯还原糖在贮藏期随温度、体积、品种以及不同时期的含量;并对正交试验数据进行了处理,得到了贮藏期还原糖含量受诸多因素影响的变化关系,结果表明,正交试验法是一种行之有效的研究方法。     

Influence of stem canker (Rhizoctonia solani Kühn) on tuber yield,tuber size,reducing sugars and crisp colour in cv. Record

Summary In eight experiments in 4 years, inoculating seed tubers withR. solani caused stem canker and in seven experiments decreased the total yield and the yield of tubers 40–70 mm. Yields of larger tubers were usually increased. In most experiments inoculating increased the reducing sugar content of the tubers and darkened the colour of crisps, but did not consistently affect the amounts of sucrose. Treating soil with aldicarb or oxamyl before planting also slightly increased the total reducing sugars.     

马铃薯不同品系贮藏期品质分析

马铃薯秋天入窖后,测定不同品系的还原糖含量、可溶性糖含量、淀粉含量,其结果为:还原糖含量入窖后到次年3月份逐渐升高,之后又快速下降,6-21还原糖含量最低,小白花还原糖含量最高;可溶性糖含量较稳定,只是不同品系表现趋势不同,6-21可溶性糖含量最低,1-38可溶性糖含量最高;淀粉含量也较稳定,6个品系总趋势为逐渐下降;1-38淀粉含量最高;大多数马铃薯品系的还原糖与可溶性糖呈正相关,可溶性糖与淀粉、还原糖与淀粉呈负相关。     

Effect of static loading on sugar contents and activities of invertase, UDP-glucose pyrophosphorylase and sucrose 6-phosphate synthase in potatoes during storage

Summary Potatoes with an applied load of 196 N (20 kgf) were stored at 7°C for 60 days. The sugar contents (glucose, fructose and sucrose), invertase, UDP-glucose pyrophosphorylase (UGPase) and sucrose 6-phosphate synthase (SPS) of the potatoes were measured at intervals during storage. The aim of this study was to determine whether static loading affects the sugar contents and enzymes levels in potatoes during storage. Static loading increased the glucose, fructose and reducing sugar contents, as well as the invertase activity of potatoes during storage. The reducing sugar content of static loaded potatoes was correlated (P<0.01) with the invertase activity.     

Preconditioning and storage of chemically immature Russet Burbank and Shepody potatoes

Russet Burbank and Shepody potatoes of different chemical maturities (i.e. varying sucrose concentrations) at harvest were preconditioned by holding at 15 C for various durations to lower the concentration of reducing sugars to levels acceptable for processing as french fries out of 8 C storage. In chemically immature tubers (i.e. those harvested with a high sucrose), sucrose declined after harvest and stabilized in storage regardless of the preconditioning period. However, there was a temporary small increase in sucrose after harvest in more chemically mature tubers. The concentrations of the reducing sugars glucose and fructose were low at harvest, usually < 1.0 mg g^?1, but increased rapidly during the first 30 to 45 d of storage in tubers with more than 2.0 mg g^?1 sucrose at harvest. Preconditioning for up to 70 d at 15 C either limited the increase in reducing sugars or lowered them more rapidly during storage than when preconditioned for only 14 d. Fresh weight loss of Russet Burbank and Shepody was greater in physically and chemically immature tubers compared to more mature tubers. Extended preconditioning of Russet Burbank and Shepody resulted in minimal additional weight loss.     

The effect of storage temperature on reducing sugar concentration and the activities of three amylolytic enzymes in tubers of the cultivated potato,Solanum tuberosum L.

Summary Reducing sugar content, and activities of three starch hydrolysing enzymes, alpha-amylase, beta-amylase and debranching enzyme were measured over several months in tubers of five cultivars stored at 4°C or 10°C. Cultivars differed in their sensitivity to storage temperature. Reducing sugar content of tubers and the activities of three starch hydrolysing enzymes increased sharply during the first weeks of storage at 4°C. At 10°C, reducing sugar content, and the activity of the three enzymes remained constant or increased only slightly. Deceased.     

Changes in sugar content and invertase activity in tubers of some Indian potato varieties stored at low temperature

Summary Significant differences were found in sugar content and invertase activity of tubers of 8 Indian cultivars stored at 3–5°C. Freshly harvested tubers of all the cultivars had low amounts of sugars, which increased during storage, and little or no basal invertase activity but both basal and total invertase activities in all the cultivars increased during storage. There were significant correlations between the reducing sugar content and basal and total invertase activities. Publication no. 116, Central Potato Research Institute, Shimla.     

Storage temperature and maleic hydrazide effects on sprouting,sugars, and fry color of Shepody potatoes

The effect of low storage temperature (4 to 8 C) and maleic hydrazide (MH) treatment on sprouting, sucrose and reducing sugar (glucose and fructose) concentrations in tubers, and fry color-sugar relationships of Shepody were determined and compared to Russet Burbank. Sprouting of Shepody was delayed by 3 to 15 weeks when the temperature was lowered from 8 to 6 or 5 C, respectively. Shepody accumulated more sugars at all storage temperatures than Russet Burbank. The reducing sugars accumulated in Shepody at 5 and 6 C could be lowered to levels acceptable for processing for about 24 weeks after harvest by reconditioning at 18 C for at least two weeks. MH increased glucose in Shepody stored at 5 C compared to untreated tubers. Excessive sprouting (> 10 cm sprout length) of nonsprout inhibited Shepody occured late in storage with four weeks reconditioning. Although not statistically significant, MH tended to cause darker fry color per unit of reducing sugar in Shepody compared to tubers from untreated plants. Storage of Shepody tubers not treated with MH could be extended a few weeks by temperatures < 8 C only if there is precise control over temperature, sugars are closely monitored, and reconditioning is rapid to minimize sprouting.