Processing Quality Of Potatoes Research Articles

Effects of Nitrogen and Potassium on Yield and Quality Of Potato (Solanum Tuberosum L.) Cultivars

Effects of nitrogen (N) and potassium (K) fertilization rates on the yield and quality of two potato cultivars, Asterix and Courage were conducted. The treatment combination of N2K2 (N2: 140 kg ha−1 and K2: 152 kg ha−1) had the highest total yield (31.38 and 22.51 t ha-1), marketable tuber yield (29.08 and 20.49 t ha-1) and chips potato yield (36.63 and 36.96%) of the 18 treatment combinations for Asterix and Courage cultivar, respectively. The treatment combination of N2K2 had also the highest specific gravity (1.07 and 1.17 gcm-3), dry matter (22.65 and 22.77%), firmness (45.13 and 42.92 N), and lowest total soluble solid (4.30 and 4.23 oBrix) in both the cultivars, whereas the colour of the chips revealed the least crispness (0.15 and 0.17 N). In order to enhance potato processing quality without reducing production, a lower N and higher K treatment combination may be employed. Bangladesh J. Bot. 52(2): 267-275, 2023 (June)

The transcription factor StTINY3 enhances cold-induced sweetening resistance by coordinating starch resynthesis and sucrose hydrolysis in potato.

The accumulation of reducing sugars in cold-stored tubers, known as cold-induced sweetening (CIS), negatively affects potato processing quality. The starch to sugar interconversion pathways that are altered in cold-stored CIS tubers have been elucidated, but the mechanism that regulates them remains largely unknown. This study identified a CBF/DREB transcription factor (StTINY3) that enhances CIS resistance by both activating starch biosynthesis and repressing the hydrolysis of sucrose to reducing sugars in detached cold-stored tubers. Silencing StTINY3 in a CIS-resistant genotype decreased CIS resistance, while overexpressing StTINY3 in a CIS-sensitive genotype increased CIS resistance, and altering StTINY3 expression was associated with expression changes in starch resynthesis-related genes. We showed first that overexpressing StTINY3 inhibited sucrose hydrolysis by enhancing expression of the invertase inhibitor gene StInvInh2, and second that StTINY3 promoted starch resynthesis by up-regulating a large subunit of the ADP-glucose pyrophosphorylase gene StAGPaseL3, and the glucose-6-phosphate transporter gene StG6PT2. Using electrophoretic mobility shift assays, we revealed that StTINY3 is a nuclear-localized transcriptional activator that directly binds to the dehydration-responsive element/CRT cis-element in the promoters of StInvInh2 and StAGPaseL3. Taken together, these findings established that StTINY3 influences CIS resistance in cold-stored tubers by coordinately modulating the starch to sugar interconversion pathways and is a good target for improving potato processing quality.

StRAP2.3, an ERF\u2010VII transcription factor, directly activates StInvInh2 to enhance cold-induced sweetening resistance in potato

Potato invertase inhibitor (StInvInh2) positively regulates cold-induced sweetening (CIS) resistance by inhibiting the activity of vacuolar invertase. The distinct expression patterns of StInvInh2 have been thoroughly characterized in different potato genotypes, but the related CIS ability has not been characterized. The understanding of the regulatory mechanisms that control StInvInh2 transcription is unclear. In this study, we identified an ERF‐VII transcription factor, StRAP2.3, that directly regulates StInvInh2 to positively modulate CIS resistance. Acting as a nuclear-localized transcriptional activator, StRAP2.3 directly binds the ACCGAC cis-element in the promoter region of StInvInh2, enabling promoter activity. Overexpression of StRAP2.3 in CIS-sensitive potato tubers induced StInvInh2 mRNA abundance and increased CIS resistance. In contrast, silencing StRAP2.3 in CIS-resistant potato tubers repressed the expression of StInvInh2 and decreased CIS resistance. We conclude that cold-responsive StInvInh2 is due to the binding of StRAP2.3 to the ACCGAC cis-element in the promoter region of StInvInh2. Overall, these findings indicate that StRAP2.3 directly regulates StInvInh2 to positively modulate CIS resistance, which may provide a strategy to improve the processing quality of potatoes.

Quest for Suitable Storage Condition for Sustainable Processing Quality of Potato Tubers

Processing quality of potato tubers depend on the physico-chemical properties which changes within the time in long-term storage period. The present study was conducted to find out a suitable storage condition that could be able to maintain the processing quality of potatoes. Three potato varieties namely Asterix (BARI Alu-25), Courage (BARI Alu-29) and Lady Rosetta (BARI Alu-28) and three different storage conditions viz. Bamboo chamber (BC), earthen chamber with evaporative cooler (EC) and refrigerator (RF) were used in this study. Data were recorded monthly-basis on the physico-chemical processing qualities of the potato tubers. Potato tubers stored in RF was able to maintain higher dry matter content and lower weight loss, shrinkage and energy content than BC and EC. Though the physical qualities of the refrigerated tubers were well-maintained, but produced considerably higher amount of mean reducing sugars (2.69 mg/g FW) which was 11.6 and 17.9% higher than the mean of BC (2.41 mg/g FW) and EC (2.28 mg/g FW), respectively; and higher mean sucrose contents (2.46 mg/g FW) which was 6.5 and 18.8% higher than the mean of BC (2.31 mg/g FW) and EC (2.07 mg/g FW), respectively. EC maintained significantly lower amount of mean glucose (0.17 mg/g FW), fructose (1.96 mg/g FW) and total soluble sugar (4.20 mg/g FW) contents than BC and RF. Compared to pre-storage, mean reducing sugar content was increased by 1.5, 1.7 and 2.0 times in EC, BC and RF, respectively until 90 days of storage and the increase in mean sucrose content was 1.7-, 2.1- and 2.3-fold in EC, BC and RF, respectively. Among the varieties, Courage and Lady Rosetta were suitable for long-term storage for processing than Asterix. Chips produced from the potatoes stored in the EC acquired significantly higher scores for sensory attributes than that of BC and RF. Results clearly depicted that potatoes stored in EC were more suitable for processing due to moderate retention of dry matter content (22.13%) and lower accumulation of different sugars and were able to retain processing quality up to 90 days of storage than that of BC and RF.
 Ann. Bangladesh Agric. (2019) 23(2) : 61-78

Influence of Harvesting Date on Chemical Maturity for Processing Quality of Potatoes

The present study was conducted to find out a suitable harvesting date of processing potato varieties (Asterix, Courage and Lady Rosetta) from three different harvest dates [80, 90, and 100 days after planting (DAP) harvest] by chemical maturity monitoring. Eighty DAP harvest resulted the lowest mean total soluble sugar (TSS) (3.77 mg/g FW), reducing sugar (RS) (1.57 mg/g FW), sucrose (2.40 mg g-1 FW), fructose (0.77 mg/g FW) and polyphenol (238.94 μg/g FW) contents in all the varieties and at the same DAP harvest, dry matter (DM) content (21.71%) and chip color index (CCI) (0.67) remained at the lowest. Tubers harvested at 80 DAP produced good quality and acceptable colored processed products as it meets up the required processing quality, but lesser DM content might increase the cost of the product. Optimum DM content (24.07%) with moderate level of different sugar contents and acceptable CCI (1.13 to 1.85, <2.00) was found at 90 DAP harvest. Therefore, 90 DAP harvest could be considered as suitable harvesting date for processing by compromising some quality parameters (TSS, RS, sucrose, fructose and polyphenol contents). Among the varieties, Lady Rosetta and Courage were preferable for producing quality potato products. Highly significant and positive correlation existed between CCI and different chemical parameters. A strong correlation coefficient (r = 0.822**) and good fit (R2 = 0.6755) of the regression equation (CCI = 0.9341RS – 0.4969) between CCI and RS indicated that RS content played the vital role in the browning of the processed potato products.
 Ann. Bangladesh Agric. (2019) 23(2) : 89-103

Inhibitory effect of tartary buckwheat seedling extracts and associated flavonoid compounds on the polyphenol oxidase activity in potatoes (Solanum tuberosum L.)

To improve the processing quality of potatoes, phosphate buffer extract (PBE), 50% ethanol (E50), and aqueous extract (AE) of tartary buckwheat seedlings were evaluated for their ability to inhibit the enzymatic browning of potatoes. The results suggest that all extracts of tartary buckwheat seedlings exert significant inhibitory effects on the polyphenol oxidase (PPO) activity in potatoes. The relative concentrations required for a 50% reduction in the PPO activity (IC50) were 0.21, 0.28 and 0.41 mg mL−1, for PBE, E50 and AE, respectively. The strongest inhibitory activity was observed for PBE, followed by E50 and AE. Four flavone compounds in the PBE of tartary buckwheat seedlings (i.e., rutin, kaempferol-3-O-rutinoside, quercetin, and kaempferol) were identified by high-performance liquid chromatography. These compounds were subsequently evaluated for their roles in the inhibition of PPO from potatoes using a model system. The results indicated that rutin exhibited the highest inhibition rate on the PPO of potato. A synergistic inhibitory effect was observed by mixing rutin, kaempferol-3-O-rutinoside, quercetin, and proteins. The inhibitory patterns of rutin, kaempferol-3-O-rutinoside, and quercetin on the enzyme were noncompetitive and reversible, with inhibitory constants of 0.12, 0.31, and 0.40 mg mL−1, respectively. Flavonoids from tartary buckwheat seedlings may exhibit a common mechanism with phenolic compounds, involving the blockage of the reaction of oxygen with PPO leading to the inhibition of the enzymes involved in browning. Based on these results, extracts of tartary buckwheat seedlings can be used as potent natural inhibitors.

Chitosan: a Safe Alternative to Synthetic Fungicides to Manage Dry Rot in Stored Potatoes

Sub-tropicalisation of potato has increased the threat of dry rot during postharvest potato storage at elevated temperatures (10–12 °C). Potatoes meant for processing are generally stored at 10–12 °C, where not only sugars accumulate during prolonged storage, also Fusarium species affects the tuber quality and leads to more losses. Therefore, the present study aimed to reduce the physiological and pathological losses by retaining the processing quality of potatoes through coating with three concentrations of chitosan (0.1%, 0.25% and 0.5%). Tubers were stored at 12 ± 1 °C with 90–95% relative humidity up to 170 days and analysed periodically. Sugar accumulation reduced with chitosan coating of tubers. Chip colour was retained in all coated as well as uncoated tubers. Coating at 0.25% chitosan showed improved chip colour compared to others. Concentration of flavouring compounds increased with increasing chitosan concentration. Chitosan coating reduced the rate of respiration and weight loss. Maximum decrease in rate of respiration with coating was 22% in cultivar Kufri Jyoti and 25% in cultivar Kufri Frysona. Weight loss decrease was 26% in Kufri Jyoti and 15% in Kufri Frysona compared to uncoated tubers. Chitosan coating reduced the Fusarium incidence significantly in dose-dependent manner. Chitosan at 0.25% concentration was able to completely inhibit Fusarium growth. Coating of whole potatoes with chitosan increased the storage life of tubers by reducing the pathological and physiological losses. Coating of tubers with chitosan prior to cold storage will help potato processors to reduce postharvest losses.

Effect of Hhydrogen Peroxide Foliar Spraying on Tuber's Quality of Three Potato Cultivars

Two field experiments concerning potato (Solanum tuberosum L.) crop werecarried out during two successive winter seasons of 2009/2010 and 2010/2011 in a private farm ata newly reclaimed area, in El-Amria region, Alexandria governorate, Egypt. The experiment wasperformed to study the effect of hydrogen peroxide (H2O2) on the potato processing quality and theeconomical characters. The split-plot design in three replicates was used, where potato cultivarswere placed in the main plots, while doses of foliar spraying with hydrogen peroxide were occupiedthe sub-plots. Three potato cultivars were tested in this investigation; Lady Rossetta, Valor andMondial. Four doses of hydrogen peroxide were used as zero, 25, 50 and 75 mM in the first year.Two higher doses, 100 and 125 mM of hydrogen peroxide were added in the second year. Potatoplant stem diameter was positively affected with the increasing of H2O2 concentrations from zero up to 125 mM. The results showed that the 25, 50 and 75 mM of H2O2 concentrations did not affect thepotato tuber yield. The other two high levels (100 and 125 mM) of H2O2 resulted in lower potatoyields. The number of tubers/ 10 Kg weight trait seemed to be affected with H2O2 concentrations, inwhich it was above the accepted number during the second year (more than 112 tubers/10 Kgweight).In the first year, the data indicated that spraying potato plants with 75 or 50 mM of H2O2significantly increased dry matter percentage compared with the control treatment. Both treatmentsof 75 and 50 mM of H2O2, produced the highest levels of tuber starch content in the first year , whilethe treatment 75 mM of H2O2, produced the highly tuber starch content with significant differencesamong the other tested treatment in the second year of the study. The effect of hydrogen peroxideon parenchyma cell diameter trait differed from year to another. The treatment of 50 mM of H2O2possessed the highest value for parenchyma cell diameter trait, whereas, the treatments of both 25and 125 mM of H2O2 increased the parenchyma cell diameter trait. The lowest chipping defectswere produced when potato plants sprayed with 50 mM H2O2. The control treatment gave thelowest mean value (result) where this treatment produced highly significant level of tuber chippingdefects.

Modulation of gene expression in cold-induced sweetening resistant potato species Solanum berthaultii exposed to low temperature

Cold-induced sweetening (CIS) is a crucial factor influencing the processing quality of potato tubers. To better understand the molecular events of potato CIS and different CIS-sensitivity among various potato species, a suppression subtractive hybridization library and cDNA microarray gene filters were developed. A total of 188 genes were found to be differentially expressed (DE) in Solanum berthaultii (ber) upon cold stimulation. These functional genes were mostly related to cell rescue, defense and virulence, metabolism, energy and protein fate, included in various processes of plant defense against abiotic stresses. Four expression patterns of these DE genes were profiled by qRT-PCR using the cold-stored tubers of both CIS-resistant (ber) and CIS-sensitive (E-potato 3, a variety of S. tuberosum) potatoes. The expression pattern and abundance of many DE genes encoding proteins involved in metabolism were different in these two potato tubers, especially genes associated with amylolysis, sucrose decomposition and glycolysis pathways, indicating distinct regulatory mechanisms between ber and E3 in response to cold stress, which may be crucial for potato CIS. Further investigation of these cold-regulated genes will deepen our understanding of the regulatory mechanisms of potato CIS and direct approaches for the genetic improvement of potato processing quality.

Zebra Chip Progression: From Inoculation of Potato Plants with Liberibacter to Development of Disease Symptoms in Tubers

Zebra chip (ZC), a new and serious disease of potatoes, has caused millions of dollars in losses to the potato industry in the United States, Mexico, Central America, and New Zealand. The disease has been associated with the bacterium “Candidatus Liberibacter solanacearum” transmitted to potato by the potato psyllid, Bactericera cockerelli (Sulc). The most characteristic symptoms of ZC develop in potato tubers and include browning of vascular tissue concomitant with necrotic flecking of internal tissues and streaking of the medullary ray tissues, all of which can affect the entire tuber. Upon tuber frying, these symptoms become more pronounced and potato chips or fries processed from ZC-affected tubers show very dark blotches, stripes, or streaks, rendering them commercially unacceptable. Field experiments were conducted to determine how rapidly ZC symptoms develop in potato tubers following plant exposure to liberibacter-infective potato psyllids and to assess how the disease affects the overall potato yield and tuber processing quality over time. Results indicated that ZC symptoms developed in potato tubers 3 weeks following plant exposure to psyllids. Tuber development ceased upon the onset of ZC symptoms, resulting in substantial yield loss. Levels of tuber solids decreased as soon as initial disease symptoms were observed. In contrast, reducing sugar levels in tubers increased dramatically upon the onset of ZC symptoms, significantly affecting potato processing quality. This information, in combination with effective psyllid monitoring and control, will assist potato producers make harvest timing decisions following infestations of potato psyllids in their fields to minimize damage caused by ZC.

Stability of eight potato genotypes for sugar content and French fry quality at harvest and after storage

Affleck, I., Sullivan, J. A., Tarn, R. and Yada, R. 2012. Stability of eight potato genotypes for sugar content and French fry quality at harvest and after storage. Can. J. Plant Sci. 92: 87–96. Processing quality of potatoes for French fries is partially determined by reducing sugar content of the tuber. Much of the potato crop is processed after a storage period when sugar content can change and affect processing quality. In this study, the stability of sugar levels in eight potato genotypes was studied over four environments (i.e., two locations over 2 yr). The GGE biplot analysis was used to measure the stability of, and the association between, quality traits and sugar content. Quality and sugar content were measured 105 and 120 d after planting and 60 and 120 d after storage. The biplots indicated a change in French fry colour scores and stability between the 105 and 120 d after planting harvest dates. Genotypic differences were noted for French fry colour scores and glucose content. Genotypes were identified that were stable for French fry colour during the two storage periods indicating low genotype by environment interaction. The GGE biplot identified mega-environments that encompassed a group of environments with similar attributes. Based on this finding potatoes from only one environment within the mega-environment would need to be stored for quality evaluations.

Prediction of Potato Processing Quality by near Infrared Reflectance Spectroscopy of Ground Raw Tubers

The technique of near infrared reflectance spectroscopy was tested to predict the processing quality of potatoes by scanning (850–2500 nm) ground raw potatoes ( n = 2517) from nine growing seasons and four to five locations. Calibration equations were developed for dry matter, starch, reducing sugars, sucrose and total sugar as well as lightness of dehydrated potatoes and potato crisps, and quality score of finished French fries. Two strategies in modelling were compared, an annually repeated (incremental) and a retrospective calculation at the end of the project with inclusion or removal of spectral outliers. The best coefficients of determination ( r2) within independent validation sets were about 0.99 for dry matter, 0.96 for starch, 0.43 for reducing sugars, 0.71 for sucrose and 0.66 for total sugar. The RPD statistic (ratio of standard error of prediction to sample standard deviation) was up to 8.5 and 5.4 (dry matter and starch content, respectively), but was unacceptably low in the case of reducing sugars (1.7) and low for sucrose (2.4) and total sugar (2.3). Direct prediction of processing quality resulted in r2 values of 0.52 for dehydrated potatoes, 0.69 for potato crisps and 0.56 for French fries, but the RPD of these models were too low even for screening purposes ( RPD < 2.0).

Cold storage, reconditioning potential and chip processing quality of spring potato (Solanum tuberosum L. cv. Hermes) tubers in response to differential nitrogen fertilisation

AbstractBACKGROUND: Crop management has been implicated in tuber sugar accumulation and potato processing quality. However, reports on potato postharvest behaviour, tuber composition and processing quality in response to crop nitrogen (N) fertilisation have been sparse and inconclusive. In this study, chipping potato cv. Hermes was treated with four preplanting N rates (0, 100, 200 and 300 kg ha−1) to evaluate the effect of N fertilisation on sugar accumulation profiles and processing quality at harvest, after cold storage at 4.5 °C for up to 200 days and after reconditioning at 16 °C for 10–30 days.RESULTS: Preharvest leaf petiole analysis and tuber nitrate analysis at harvest confirmed crop response to N rates. At harvest, tuber specific gravity decreased marginally beyond 200 kg N ha−1. Chip colour as well as tuber sucrose and reducing sugar (RS) content was unaffected by N fertilisation rate. During cold storage and reconditioning, tuber fresh weight loss and sprout growth were unaffected by N rate, while its effect on tuber sugar levels was either statistically or practically insignificant. Tuber sucrose and RS contents correlated highly with chip colour (r = − 0.729, P <0.001 and r = −0.791, P <0.001 respectively). Importantly, postharvest chip colour was also unaffected by N rate, though it declined markedly with the onset of cold storage and improved significantly throughout reconditioning. Differences in chip colour between years were limited but potentially critical in meeting the commercial standard.CONCLUSION: Completion of physiological crop senescence of the spring potato crop under Mediterranean climatic conditions seems to mitigate the potential interference of preplanting N fertilisation with tuber maturation and subsequently cold storage performance, reconditioning potential and processing quality. Copyright © 2009 Society of Chemical Industry

Molecular characterization and biotechnological improvement of the processing quality of potatoes

Fries, chips, starches, flakes, and frozen pre-cooked potatoes, such as hash browns, are currently the main products made from processed potatoes. The processing quality of potatoes is largely determined by the carbohydrates, such as starch and glucose, in their tubers. The quantitative inheritance, heritability variation, transgene pleiotropic effects, and storage condition requirement of the processing quality are partly due to the carbohydrate metabolic network plasticity in potatoes. Pathway partition of sugars influences the processing quality such as chip color. This presentation attempts to review traditionally separate but related aspects (i.e., genetics, breeding, genomics, metabolism, marker-assisted selection, and transgenic engineering) of the potato processing quality and to discuss the integrated approach to its genetic improvement. Key words: Solanum tuberosum L., French fries, chips, carbohydrate metabolism, dry matter content, cold sweetening tuber morphology, metabolic network, partition of sugars, gene expression profile, transgenic regulation

Temperature-induced changes in potato processing quality during storage are modulated by tuber maturity

Knowledge of how potato (Solatium tuberosum L.) cultivars respond to non-conventional storage temperature regimes may expand options for managing immature, overmature, or otherwise stressed potatoes. Here we demonstrate that temperature-dependent changes in the processing quality of tubers are modulated by tuber maturity. ‘Russet Burbank’ (RB), ‘Ranger Russet’ (RR), and ‘Umatilla Russet’ (UR) tubers from early- and late- planted crops (grown for 163 d and 133 d, respectively) were conditioned for a month at 4.5, 6.7, or 9 C, and subsequently stored at 4.5, 6.7 or 9 C (nine temperature regimes) for an additional 182 d before reconditioning at 16 C. Fry color darkened as conditioning temperature (CT) decreased from 9 to 4.5 C, and tubers were most sensitive to low temperatures for loss of processing quality during the initial conditioning period following wound-healing. Conditioning at higher temperatures increased the tolerance of tubers to lower subsequent holding temperatures (HT) later in the storage season. The processing quality of chronologically older (early planting) RR and UR tubers was inferior to the younger tubers (late planting), resulting in fewer CT/HT combinations for managing the former. Regardless of maturity, RR tubers maintained processing quality for up to 230 d when conditioned and stored at higher temperatures; however, tubers from the late planting had a greater tolerance of lower temperatures than those from the early planting. Although reconditioning improved the processing quality for all cultivars and thus expanded the CT/HT management options, the responsiveness of cold-sweetened UR tubers to reconditioning attenuated over the 230 d storage period, reflecting earlier onset of irreversible senescent sweetening in this cultivar. Chronologically younger tubers of the most dominant processing cultivars in the Pacific Northwest stored better than tubers produced over a prolonged growing season. Collectively, these studies suggest strategies to manage tubers of differing maturity to best preserve processing quality during storage.

Distribution of Selenium in Different Biochemical Fractions and Raw Darkening Degree of Potato (Solanum tuberosum L.) Tubers Supplemented with Selenate

Effects of Se fertilization on potato processing quality, possible changes in Se concentration and form in tubers during storage, and retransfer of Se from seed tubers were examined. Potato plants were grown at five selenate (SeO4(2-)) concentrations. Tubers were harvested 16 weeks after planting and were stored at 3-4 degrees C prior to analysis. The results showed that the Se concentration did not decrease during storage for 1-12 months. In tubers, 49-65% of total Se was allocated in protein fraction, which is less than found in plant leaves in a previous study. The next-generation tubers produced by the Se-enriched seed tubers had increased Se concentrations, which evidenced the relocation of Se from the seed tubers. At low levels, Se improved the processing quality of potato tubers by diminishing and retarding their raw darkening. The value of Se-enriched potato tubers as a Se source in the human diet was discussed.

Physiological Losses and Processing Quality of Potatoes under Ambient Temperature Storage as Influenced by Tuber Maturity

Two potato cultivars belonging to an early-maturing group were harvested at different stages of maturity directly or after a ten-day period of defoliation. Tubers were evaluated for storability and processing quality during ambient temperature storage (16.5-36.5°C, 37.4-91.3% RH). Mean tuber yield and tuber dry matter content increased up to last stage of harvest (80 days after planting). Tuber yield on fresh weight basis increased and dry matter content decreased during the ten-day period following defoliation mainly due to water uptake. Mean respiration rates of tubers decreased from 16.07 to 4.72 mg CO 2 kg - 1 hr - 1 during the curing period up to 20 days after harvest. Respiration rate one day after harvest was highest in immature tubers harvested directly 60 days after planting and rates decreased as the harvest was delayed. Harvesting trauma was minimal in mature tubers harvested 90 days after planting following a ten-day period of defoliation, where the decline in respiration rate during the curing period was minimal. Weight loss in stored potatoes was affected by harvest date with more physically immature tubers losing more weight during curing and throughout storage. Rotting in tubers up to 120 days storage was also higher in immature tubers. Defoliation of the crop ten days prior to harvest further reduced weight loss and rotting in tubers during storage. Contents of reducing sugars and sucrose in tubers were also affected by harvest date: immature tubers of both the cultivars exhibited higher amounts at harvest and during storage and produced chips of unacceptable colour. Chip colour improved with maturity of tubers. Mature tubers were found suitable for short-term non-refrigerated storage due to reduced physiological losses and acceptable processing quality.

ALTERNATIVE COMPOUNDS FOR the MAINTENANCE of PROCESSING QUALITY of STORED POTATOES (SOLANUM TUBEROSUM)

alternative sprout inhibitors were testedfortheir efficacy in retaining processing quality of potatoes during long term storage. Carvone, dimethylnaph-thalene and ethylenewere compared to the commercial standard, CIPC, (isopropyl N-(3-chlorophenyl) carbamate) and anair control, for their effects on sprout development, fry color andsugar content of potato tubers, during 25 weeks ofstorage at 9C. All treatments reducedsprouting although the amount of sprouting variedamong treatments. At the end of the 25 week storage period, the amount of sprouting based on total sprout weightand maximum sprout length was, inorder from least to most, CIPC, carvone, ethylene, DMN and air, Poorer processing quality due to darker fry dcolor and higher levels of reducing

Effect of Different Controlled Atmospheres on Processing Quality of Potatoes

Four potato cultivars responded positively to a commercial reconditioning treatment after being stored for seven months at 4 °C and 8 °C under different controlled atmospheres. CA combinations of 9.7-12% CO2 with 2.0-2.9% O2 delayed sprouting in all the cultivars. It has been found that low CO concentrations (0.7-6.3%) increased the number of sprouted eyes, and increased sprout growth in Saturna and Panda respectively. The highest weight loss after reconditioning was found in the potatoes which has previously been stored in the gas combination of 0.9% CO2 and 21% O2, while the gas combinations with high CO2 showed the lowest weight loss after reconditioning. Results also indicated that the fry colour on the surface of crisps produced from all the cultivars for most of the CA combinations, at both temperatures, was lighter than that obtained after curing.

Effect of low‐temperature storage, gamma irradiation and iso‐propyl‐N‐(3‐chlorophenyl carbamate) treatment on the processing quality of potatoes

AbstractIn Taiwan commercial storage of potatoes (CV Kennebec, Wu‐Foon, Cardinal) at 2°C. 85% RH, can supply the fresh market all year round. However, reducing sugar and total sugar which accumulate in the tubers will reduce the processing quality of potatoes. Reconditioning of tubers from cold stores was undertaken at ambient temperature (20°C) for up to 6 weeks. The optimum temperature for Kennebec and Cardinal reconditioning ranged from 20 to 25°C. However, after storage at 2°C for a long period, the sugar content of potato tubers cannot be reduced to a satisfactory level. When newly harvested potatoes were pretreated with CIPC (300–500 μg litre−1) and stored at 10°C, 80 % RH, sprouting was inhibited effectively. The quality of potatoes was retained well and reducing sugar remained at a low level for up to 8 months. MENA was found to be ineffective. Gamma irradiation of potatoes at 0.175‐0 20·0‐10–0.125 and 0.125 kGy for Cardinal, Kennebec and Wu‐Foon respectively was found to be effective in controlling the sprouting of tubers stored at 10°C, 80 % RH, for 9 months. A rapid increase in sugar content was found in irradiated Cardinal and Wu‐Foon after storage for 7 months, while the reducing sugar in irradiated Kennebec was still below 0°2 % after 8 month's storage. Gamma irradiation had no adverse effect on the ascorbic acid content, and higher firmness retention was obtained in irradiated tubers throughout storage at 10°C.