Relationship of sucrose synthetase cleavage activity to the chemical and physical maturity of Norchip and Kennebec potatoes

A role for sucrose synthetase in the development of Kennebec and Norchip potatoes is supported by its high activity evident in immature tubers. The total activity per tuber increased markedly after tuberization and remained at a constant elevated level for the majority of the growing season. Its activity per tuber demonstrated a sharp decline when both varieties reached a certain degree of chemical and physical maturity. When the activity was expressed as units per gram of potato or per mg protein, two apparent decreases were evident during tuber development. A gradual decline occurred early in the season from July 21 to August 25 and a smaller more abrupt drop occurred in mid-September. The latter reduction, which lowered the sucrose synthetase activity to almost zero, corresponded with the time when the tuber reached its average mature size, when the mg of extractable protein was maximized, and when visible physical deterioration of foliage was noted. When Kennebec and Norchip potatoes reached a certain state of physiological maturity, sucrose synthetase had apparently fulfilled its function in relation to tuber development. It is suggested that these similar physiological states might be indexed by a sucrose synthetase cleavage activity which decreases to approximately 3 units per gram of potato, and/or drops to 1000 units or less per tuber.     

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.     

The effects of handling on chip color and sugar content of potato tubers

Color of chips made from potatoes (Solanum tuberosum L.) subjected to handling treatments was darker than of non-handled tubers in nine of ten experiments. ‘Monona’ and ‘Rosa’ appeared to be more vulnerable to the adverse effects of handling than were ‘Kennebec’ and ‘Norchip,’ but all cultivars were affected. Levels of fructose and glucose were elevated by handling. Sucrose also increased in all cultivars except ‘Kennebec.’ The handling effect was most noticeable early (December) or late (March or April) in the storage season. The effect of chilling did not appear to be intensified by handling.     

Ac novachip: a new potato cultivar with excellent chip quality after long storage and reconditioning

AC Novachip is a smooth, white-skinned potato cultivar with oval to oblong tubers and a maturity similar to Kennebec. It has excellent chip quality, especially after long storage and reconditioning. The boil and bake quality is similar to Kennebec; the specific gravity is higher than Kennebec but lower than Atlantic. AC Novachip has moderate resistance to common scab and PVY.     

Potato chip color,specific gravity and fertilization of potatoes with N−P−K

The effects of fertilizers on potato chip color were studied over a period of 11 years. Yield and specific gravity data also were taken. Single element and compete fertilizers were used in randomized block and split plot experiments. Most of the work was done with the Russet Burbank variety but in some experiments the Kennebec, White Rose, Norgold Russet and Cascade varieties were also included. Specific gravity and chip color data were taken immediately after harvest. Effects of storage and reconditioning on chip color were recorded in some cases. Though statistically significant effects of N?P?K on chip color were found, the differences were small and of no commercial importance. Neither nutrient balance nor total amount of fertilizer used greatly affected chip color whether the tubers were harvested “immature” in July or in October after the vines were dead. The greatest effect of over-fertilization was on the specific gravity of the tubers. As amount of fertilizer applied increased, specific gravity often decreased which would reduce the amount of processed product per unit of fresh produce. Since most manufacturers of processed potatoes prefer high specific gravity tubers perhaps varieties should be grown specifically for the processing industry. Since proper fertilization did not have a commercially important effect on chip color but greatly increased the yield, farmers should fertilize for maximum production when growing potatoes for potato chips.     

Potato glycoalkaloids: Increases and variations of ratios in aged slices over prolonged storage

Four commercial cultivars of potatoes were maintained under normal storage conditions at 44 F for 34 weeks. Except for a final 10 week interval tubers were withdrawn at 6 week intervals. After slicing, a portion of the slices was immediately analyzed for total glycoalkaloid content. The remaining slices were aged for four days in the dark at room temperature, then similarly analyzed. The total glycoalkaloid content of the aged slices increased dramatically on aging. This increase on aging of slices reached a maximum early in storage then decreased gradually over the storage period. In determining the individual glycoalkaloids, α-solanine and α-chaconine both increased in these slices, but the greatest increase was in the former. Appearing solely in the aged slices of the Kennebec variety, α-and β-solamarine appeared early in the storage period and gradually decreased over the storage period. Analyses of the unaged slices indicated that the glycoalkaloid content and composition of the potato tubers was little affected by storage. Aging of potato sprouts did not change their glycoalkaloid content.     

Yield and relationships among tuber size,sucrose and chip color in six potato cultivars on various harvest dates

Cultivars were harvested biweekly for yield, weekly for sucrose determinations, and stored for chipping. At the last harvest Crystal was highest in total and marketable yield. Specific gravity was higher in Lemhi, Russet Burbank, and Norchip than in Kennebec, Crystal and Dakchip. Storage tests showed Norchip had superior chipping color to other cultivars. Dakchip had better color after short rather than after long-term storage, while the opposite was true for Kennebec and Russet Burbank. Lemhi and Crystal were marginal in color throughout storage. Sucrose (mg sucrose/g fresh tuber) expressed as a sucrose rating (SR) ranged from 1.2 to 11.9 among the various cultivars and harvest dates. Correlation between SR’s and tuber size within cultivars ranged from ?.91 to ?.97. Variability in sucrose content of immature tubers explained 70% of the variability in chip color among cultivars after storage from four to six months. Sucrose levels may be used to predict relative chipping quality of various cultivars after moderate to long-term storage if measured during early tuber development when differences in sucrose concentration are greatest among cultivars.     

Factors influencing reconditioning of Russet Burbank potatoes

Studies were made to determine factors which influence reconditioning of Russet Burbank tubers. Tubers from plants grown under low fertility were more difficult to recondition than tubers from plants adequately fertilized. Low specific gravity potatoes were also more difficult to recondition than high specific gravity potatoes even though the initial sugar content was approximately equal. The stem portion of Russet Burbank tubers lost considerably less sugars than the bud portion during the reconditioning process. It appears that factors which are responsible for high sugar development are also responsible for difficulty in sugar loss. Results also indicate greater difficulty in reconditioning early in the storage period with the loss of sugars becoming easier as the storage season progressed into spring.     

Sensory quality of Ontario potatoes compared with principal varieties grown in Maine

Baked potatoes of five varieties grown at the same location in Maine were evaluated for quality shortly after harvest and after six months’ storage by sensory panels of 16 and 18 members. The Ontario variety was rated significantly poorer (P = 0.05) in flavor than Russet Burbank, Katahdin, and Superior, but did not differ from Kennebec when tested in November. Following storage, however, these differences were not significant. At the 1% level of detection, Ontario tubers were judged significantly less mealy than those of the Russet Burbank, Katahdin, Superior, and Kennebec varieties (Nov. Kennebec excepted) and were grayer (Mar. Superior excepted). Due to the low mealiness ratings and grayness of flesh, tubers of the Ontario variety were considered less desirable for table stock than potatoes of other principal varieties grown in Maine.     

Changes in the content of L-ascorbic acid,glucose, fructose,sucrose and total glycoalkaloids in potatoes (cv. Bintje) stored at 7, 16 and 28°C

Summary We investigated the changes in the content of L-ascorbic acid (L-AA), glucose, fructose, surose and total glycoalkaloids (TGA) during storage of potatoes, cv. Bintje, for 12 weeks at 7,16 and 28°C. The initial amount of L-AA was 8.2 mg/100g fresh weight; after 12 weeks' storage at 7°C it had decreased, while at 16 and 28°C it had increased. The sugar content went up most in potatoes stored at 28°C, but remained below the level at which potatoes taste sweet. The sugar content rose slightly at 16°C, while it decreased in tubers stored at 7°C. The initial TGA content, in equivalent amounts of α-solanine, was 3.6 mg/100 g fresh weight; after 12 weeks' storage it had decreased slightly at all three storage temperatures.     

Potato sprout inhibition and tuber quality after treatment with high-energy ionizing radiation

The use of industrial-type linear accelerators may be an alternative treatment for controlling sprouts in potatoes during long-term storage. The technical aspect of treatment has been described and may include largescale treatment of bulk potatoes as they are moving along a system of conveyors either to or from storage. The objective of the study was to evaluate the use of a linear accelerator for long-term sprout control under commercial storage conditions and the effects on tuber quality. An 18-MeV linear accelerator was used to provide sprout-inhibiting irradiation to various lots of ‘Russet Burbank’ potatoes. Successful sprout suppression was achieved with doses of 40 to 50 Gy (0 g sprout weight after 9 months of storage at 7.2 C) while higher doses caused undesirable increases in reducing sugars in the tubers. Glucose concentrations of treated tubers (0.25% fresh tuber weight) were higher after treatment than the untreated controls (0.08%), but returned to control levels after 2 to 6 months in storage. Glucose concentrations in treated tubers were significantly reduced with storage management for reconditioning by increasing the storage temperature for one month (from 7.2 C to 14.4 C) resulting in glucose concentrations near control concentrations. By increasing the dose-rate from the accelerator, recovery of tuber glucose concentration due to radiation treatments was significantly faster than when the dose was given more slowly. Potato tubers irradiated with high rates (100 Gy) of high-energy electrons exhibited an increase in soft rot and dry rot incidence in storage. Disease development in potatoes treated with sprout inhibiting doses of radiation (50 Gy) increased in lots with a high rot potential. Treated lots with low rot potential were successfully stored for 8 months or more without an increase in rot potential or shrinkage. Selection of lots for irradiation treatment should include some preliminary evaluation for development of disease in long-term storage.     

Incidence of mechanical injury to potatoes during certain storage-related handling operations in the Red River Valley production area

Injury to potatoes during three commercial harvesting and bin-filling operations in the Red River Valley of Minnesota and North Dakota averaged 46.9%. The varieties Norchip, Kennebec, and Viking averaged 24.1, 64.5, and 73.2% respectively in these observations. The Kennebec potatoes, which had the most injury at bin filling, had the least decay at the end of the storage period. Loss of weight during storage averaged 2.04, 2.33 and 1.75 g/kg of potatoes per week, respectively for the Norchip, Kennebec and Viking tubers. During bulk scoop operations none of the factors: type of bucket, condition of pile, or operating speed significantly influenced handling damage.     

The effects of ozone and 1,8-cineole on sprouting,fry color and sugars of stored Russet Burbank potatoes

Ozone and 1,8-cineole were investigated as alternatives to isopropyl-n-(3-chloro-phenyl)carbamate (CIPC) to control sprout development of potato (Solatium tuberosum) tubers cv Russet Burbank during long-term storage. Sprout development was similar in ozone-treated and air-stored tubers, but both had much larger and more numerous sprouts than CIPC-treated tubers. Sucrose and reducing sugars in ozone-treated tubers were similar to levels in air-stored potatoes. Fry color was not different among potatoes stored in ozone, air and CIPC. Conversely, potatoes treated with 1,8-cineole did not produce any sprouts during the 25 week study. The fry color of tubers exposed to cineole was darker than either air-stored or CIPC-treated tubers. Sucrose and reducing sugar levels were higher in cineole-treated tubers than in tubers treated with CIPC.     

Inheritance of glucose content in tubers of diploid potato families

During two consecutive years 17 unselected families of diploid potatoes in comparison to their parents and standard cultivars were assessed for glucose content in tubers. Glucose content was evaluated using Potato Test Strips in tubers stored at 10 C, 4 C, and 4 C followed by reconditioning at 18 C. Distribution of glucose content in families indicated that the trait is inherited in a polygenic way. Transgressive individuals in families in comparison to respective parents were found in all treatments applied. Maternal effect on glucose content in tubers was found in one out of three tested families after cold storage (4 C) and the same families after reconditioning. Analysis of variance showed significant influence of year on the trait. Significance of GCA and SCA showed that both additive effects and genetic interactions are involved in determining of glucose content in tubers in all applied treatments. It was found that glucotests can be recommended for evaluation of chipping ability in early stages of selection.     

Influence of potato storage and handling stress on sugars,chip quality and integrity of the starch (amyloplast) membrane

Mechanical handling of Norchip (cv.) potatoes resulted in sucrose concentrations that exceeded 1% (fresh wt basis) 10 days after treatment. More than 65% of the maximal sugar accumulation occurred within 5 days of handling. Potatoes increased in their ability to produce sucrose as storagetime increased. Sucrose accumulation in response to handling stress was not mediated via gross physical disruption of the amyloplast membrane. Electron micrographs indicated that starch granules of both handled and control potatoes were surrounded by intact and continuous plastid (amyloplast) membranes throughout the major portion (1 to 8 months) of the storage season (8.9 C). Glucose levels did not increase at a similar rate compared to changes in sucrose concentration. Results suggest that the majority of the sucrose, which occurred during storage and/or handling stress, was not efficiently converted to reducing sugars via the enzyme invertase. Sucrose and glucose concentrations in all potatoes began to increase and chip color darkened as tubers senesced (9 to 10 months storage). Examination of electron micrographs during this storage period revealed that the bi-layers of the amyloplast membrane were separating. The mechanical handling of senescing potatoes (10 months in storage) resulted in a shift of the plastid membrane to a more disrupted state over that noted in the control. The variation in chip color induced by handling and/or storage time in Norchip potatoes was closely associated with the variation in glucose content (r = 0.953).     

Differential response of cold stored potato tubers to ethylene

The chip color of two potato varieties (Monona and Kennebec) processed directly out of 40 F storage changed in different directions after short exposure to ethylene and continued cold storage. Monona tubers produced much darker chips after ethylene treatment whereas non-enzymatic browning of Kennebec chips was considerably less after gassing. The distribution of pigmentation in chips prepared from both tubers was more uniform after ethylene treatment.     

Potato composition: I. Tissue selection and its effects on solids content and amylose/amylopectin ratios

Solids content and amylose/amylopectin ratios were determined in different parts of tubers of White Rose, Red La Soda, Kennebec, Russet Burbank, Norchip and Lenape at harvest, after storage at 7 C for 2 and 4 mo, and after reconditioning at 20 C for 3 wk following each storage period. In all cultivars, solids content was greatest in stem-end, lower in bud-end and lowest in core tissue. The relationships for distribution of solids among the different parts of the tubers was not changed by storage treatments in any of the cultivars. Amylose/amylopectin ratios were similar in all parts of the tuber. Both the solids content and amylose/amylopectin ratio were changed by storage, but not uniformly in all cultivars.     

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.     

Changes in ascorbic acid content during growth and short-term storage of potato tubers (Solanum tuberosum L.)

Changes in ascorbic acid levels were followed in apical and basal portions of Russet Burbank and Kennebec tubers during growth and development. Influence of nitrogen fertilization during growth and short-term storage on ascorbic acid level of the tuber was also studied. Changes in ascorbic acid content during growth showed two distinct phases, the first phase being characterized by an increase in ascorbic acid content with growth and development of the tuber, followed by a second phase which showed a decrease in ascorbic acid content with increasing maturity. The shift from the first phase to the second phase occurred earlier for Kennebec than for Russet Burbank. Increased nitrogen fertilization resulted in a delay of this shift from the first to the second phase. The apical portion of the tuber consistently showed higher ascorbic acid content than the basal portion. Kennebec tubers were higher in vitamin C content than tubers of Russet Burbank cultivar. High nitrogen fertilization resulted in less ascorbic acid content during growth. Storage of tubers for four weeks at 5.5°C also resulted in a marked decrease in ascorbic acid content of tubers. Nitrogen fertilizer rate during growth had no influence on the decrease in ascorbic acid content of tubers in storage.     

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.