Influence of low fertility and vine killing on sugar development in apical and basal portions of Russet Burbank potatoes

Russet Burbank tubers from plants which died prematurely (low fertility plots) accumulated significantly greater amounts of reducing sugars in storage than tubers from plants which were adequately fertilized. Also, a significantly greater difference in relative amounts of reducing sugars between the apical and basal portions was obtained from tubers of the low fertilizer regime. The basal portion had a three times greater amount of sugars than the apical portion. This is of particular interest to processors of French fries who try to obtain uniformity of color in processed fries. The difference in total reducing sugar accumulation in storage between tubers of high and low fertilizer regimes was greater at the lower storage temperatures. Tubers allowed to mature in the ground (second harvest date) accumulated less sugars in storage than tubers dug shortly after vine kill.     

Starch-sugar interconversion inSolanum tuberosum L. II. Influence of membrane permeability and fluidity

A strong relationship was found between membrane permeability and starch to sugar conversion in stored potatoes. Tissue from tubers stored at low temperature had higher sugar content and more permeable membranes than from that of tubers stored at high temperature. Tubers, moisture stressed during growth and stored at 5.5 C, accumulated more reducing sugars and had more permeable membranes than tubers from normally irrigated plants when stored at the same temperature. The basal portion of Russet Burbank tubers accumulated more sugars and was also found to have significantly more permeable membranes than the apical portion. Examination of membrane order with spin-labeled lipid probes showed that the order parameter of amyloplast membranes was less at low temperatures than when measured at higher temperatures. Membranes examined with spin-labeled lipid probes from tubers stored at 5.5 C and 15.5 C showed similar order parameters at all temperatures measured between 0 and 25 C with a linear decrease in S values at higher temperatures. These results strongly indicate a physical change of membranes with changing temperature, thus influencing sugar accumulation, which is also reversible, as indicated by loss of sugars during the reconditioning process.     

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.     

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.     

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.     

Biochemical and molecular control of cold-induced sweetening in potatoes

The benefits of being able to process potatoes directly into chips or fries from cold storage (2 to 4 C) include less shrinkage, retention of dry matter, decreased disease loss, extended marketability, and the elimination of the need for dormancy-prolonging chemicals. Unfortunately at low temperature, potato tubers undergo a phenomenon known as cold-induced sweetening where the rate of conversion of starch to reducing sugars (i.e., glucose and fructose) is accelerated. As raw potatoes are sliced and cooked in oil at high temperature, the accumulated reducing sugars react with free amino acids in the potato cell forming unacceptably brown- to black-pigmented chips or fries via a non-enzymatic, Maillard-type reaction. Potatoes yielding these unacceptably colored products are generally rejected for purchase by the processing plant. All commercial potato cultivars presently used for the production of potato chips and fries accumulate excess free reducing sugars when exposed to cold stress. If a “cold-processing potato” was available, energy savings would be realized in potato-growing regions where outside storage temperatures are cool. In regions where outside temperatures are moderately high, increased refrigeration costs may occur. This expense would be offset, however, by removal of the need to purchase dormancy-prolonging chemicals, by a decreased need for disease control and by improvement of long-term tuber quality. The primary goal of this review is to describe recent research of a biochemical and molecular nature that relates to the underlaying mechanisms regulating post harvest, cold-induced sweetening in potato tubers. No attempt was made to outline the extensive research conducted on the genetic manipulation of carbon metabolism between starch and free sugars during photosynthesis and/or during potato development in relation to source/sink interactions.     

吉林水稻品种耐冷性研究

冷害胁迫是造成水稻减产的重要因素。为探讨不同水稻品种的抗冷性,以吉林省25个主栽品种为材料,测定分析了在冷害胁迫条件下这些品种的脯氨酸、丙二醛、叶绿素及可溶性糖含量的变化情况。结果表明,所有参试水稻品种在冷害胁迫下其游离氨基酸含量升高,丙二醛含量显著增加;吉粳515、通禾66及秋田小町脯氨酸积累较多;与常温条件下相比,吉粳809、吉宏9和通禾66的叶绿素含量冷害胁迫下变化不是很显著,生长较好,耐冷性较为突出;吉粳515 、吉农大538和吉农大853在冷害胁迫条件下积累了更多的可溶性糖,进而提高了抗逆性;吉香6、宏科88抗冷性较弱,在栽培过程中,应注意对低温冷害的防御。     

Carbohydrate metabolism during tuber initiation in potato: A transient surge in invertase activity marks the stolon to tuber transition

Summary The relationship between carbohydrate metabolism and tuber initiation in potato was determined by monitoring changes in the amount of starch and sugars along with the activities of sugar metabolizing enzymes upon transfer of plants to tuber-inducing conditions (TI; short days, cold nights) from non-inducing conditions (NTI: long days, warm nights). Switch to TI conditions caused an immediate slow-down in plant growth and triggered swelling of stolon tips, which went on to develop into tubers. Leaves of plants moved to TI conditions accumulated less starch and sugar while their stolon tips showed a sudden upsurge in starch content and a sharp decline in sugars even before any tip swelling was detectable. These changes were paralleled by a transient surge in the activity of cell wall invertase (74%) and soluble invertase (30%) in stolon tips of plants transferred to TI conditions in two unrelated cultivars under different experimental conditions. As the surge in invertase activity faded, it was replaced by a substantial increase in sucrose synthase activity as the tuber enlargement proceeded. The transient increase in invertase activity just prior to tuber initiation appears to mark a turning point in the transition of stolon tip to tuber.     

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     

Predictive Markers for Cold-Induced Sweetening Resistance in Cold Stored Potatoes (<Emphasis Type="Italic">Solanum tuberosum</Emphasis> L.)

An approach has been developed to screen a large number of potato clones for cold induced sweetening (CIS) resistance in breeding programs. Two key enzymes responsible for reducing sugar accumulation during cold storage were identified. Clones with the A-II isozymes of UDP-glucose pyrophosphorylase coupled with low activity of vacuolar acid invertase enzyme had increased resistance to CIS by forming less suc, which is subsequently hydrolyzed to the undesirable reducing sugars, glc and fru. Six named cultivars and 192 genetically diverse clones from various breeding programs in USA were analyzed over two years for the two key enzymes and sugar concentration in cold stored tubers. The predictability for CIS resistance during cold storage was 94% both years. Clones classified as class A accumulated low concentration of reducing sugar glc during cold storage. It is suggested that these two predictor enzymes can be used for screening parents and selections in potato breeding program.     

Relationship of harvest sucrose content to processing maturity and storage life of potatoes

Potatoes capable of reaching low sucrose levels prior to harvest demonstrate superior processing maturity for chipping directly from intermediate temperature storage (11.7C, 53F). Forty-nine of fifty-three potato clones with a harvest sucrose rating (SR= mg sucrose/g tuber) between 1.0 and 2.8 chipped long term from storage (7.0 to 11.0 months). Eleven of twelve clones with an SR greater than 2.8 accumulated reducing sugars at a rapid rate and showed short term storage potential (0.5 to 5.3 months). A correlation coefficient of -0.845 was obtained by comparing the harvest SR value to the log₁₀ of storage life with all clones sampled over two growing and storage seasons. A standard sucrose rating (SR) procedure is described to rapidly detect annual variation in processing potato maturity to aid in determining proper post-harvest storage and utilization practices.     

Accumulation of reducing sugars by sugarcane: effects of crop age,nitrogen supply and cultivar

Sugarcane was grown under full irrigation in Australia, South Africa and Hawaii. N fertiliser was supplied at a high rate and was non-limiting to biomass accumulation in all but one dataset, where zero and high nitrogen (N) supply regimes were imposed. Crops were sampled for biomass, sucrose, glucose and fructose content of stalks. In one study, the biomass and sugar content of all green crop components were also determined. The objective was to compare the accumulation of reducing sugars, glucose and fructose, with sucrose, and how this responds to agronomic manipulations of crop duration, cultivar and nitrogen supply. Such knowledge can be used to assess the scope for maximising, by agronomic or genetic means, the partitioning of biomass to the economic product, sucrose and maximising the purity of juice for efficient sucrose extraction at the mill. At 12 months growth, 30–50% of reducing sugars was present in the stalk component, but at earlier stages was higher at 50–80%. Stalk yields of reducing sugars for 12 month crops were less than 100 g m⁻², which was less than 5% of total sugars in the stalk. There were strong effects of N supply and cultivar on the amounts and concentration of reducing sugars in the stalk at low yields, but little effect when stalk biomass exceeded about 4000 g m⁻² suggesting that, agronomic or genetic manipulation of levels of reducing sugars will only be effective early in the season. For a given level of stalk biomass, cultivar effects on partitioning to reducing sugars were due either to differences in partitioning of stalk biomass to total sugars, or differences in the partitioning between sucrose and reducing sugars. On the other hand, variation in N supply only altered the partitioning between sucrose and reducing sugars. Calculations suggested that high concentrations of reducing sugars in stalks harvested at a young age or from high N supply treatments, were not expected to lower the polarimetric estimate of sucrose concentration in the juice by more than 6%. This study provides a framework to assess the impact of cultivar, crop duration, and N supply on the accumulation of reducing sugars in different production systems.     

Influence of temperature and length of storage on resistance of potato to tuber rot induced byErwinia chrysanthemi

Tubers of 11 clones ofSolanum tuberosum subsp.andigena (andigena) and 12 cultivars ofS. tuberosum subsp.tuberosum (tuberosum) were inoculated with water suspensions (5.5 × 10⁴ 5.5 × 10⁵, 5.5 × 10⁶ CFU/ml) ofErwinia chrysanthemi. Tubers were inoculated immediately after harvest and after 6 and 16 wk of storage at 4 and 23°C. Tuber rot incidence in andigena and tuberosum increased as inoculum concentration increased. Based on tuber rot severity, clones of andigena were classified as resistant, intermediate, or susceptible and cultivars of tuberosum were classified as intermediate or susceptible. Rot severity increased in all tubers stored at 4°C and in tubers of tuberosum stored at 23°C; rot did not increase in tubers of andigena stored at 23°C. Electrolyte leakage (EL), total sugars (TS), reducing sugars (RS), non-reducing sugars (NRS) and dry matter (DM) were determined in non-inoculated tubers. There was a significant positive correlation between the rate of EL, concentration of RS and tuber rot in andigena and tuberosum. Tuber rot and DM were negatively correlated in tubers of andigena; but they were not correlated in tuberosum. Clones of andigena with low EL, TS, RS, and high DM were resistant to tuber rot, and the incidence of tuber rot in these clones was much less influenced by temperature and length of storage. The influence of temperature and length of storage on susceptibility toE. chrysanthemi may be explained by increased cell membrane permeability; increased leakage of accumulated sugars in potatoes stored at 4°C could favor bacterial proliferation resulting in more disease.     

水仙鳞茎膨大期各器官可溶性糖的含量及分布

以第3年种植的水仙品种‘金盏银台’为材料,使用乙醇沉淀法制备可溶性糖测定溶液,利用蒽酮比色法测定其鳞茎膨大期不同组织和不同部位的可溶性糖含量。研究结果表明:水仙不同组织器官可溶性糖水平为:根叶中叶尖叶基主芽鳞片。水仙叶片形成的碳水化合物能够逆浓度梯度向下运输,以供给鳞片和内球进行营养积累。不同层叶片及鳞片的可溶性糖测定发现,最外层叶片及鳞片的可溶性糖水平较其它层要低,总体上呈现出由外及里的递增趋势,说明水仙不同层叶片及鳞片为整个鳞茎的营养供给是通过由外及里,由上到下一层层供给生长需求的。     

水、陆稻在水田、旱地栽培的生态适应性研究：II．稻株碳、氮代谢的生态适应性观察

 旱种条件下，不论水稻还是陆稻，全糖、全氮含量均高于水种条件，醇溶糖占全糖的比例较高，碳／氮比低：陆稻的醇溶糖占全糖的比例远远高于水稻，这一特性很少随种植条件的改变而产生很大的变化，这可能是其对旱地适应性较强的生理原因之一。同时发现，贮藏性物质的增加是水稻旱种条件下的重要生理表现。     

Contents and digestibility of carbohydrates of mung beans (Vigna radiata L.) as affected by domestic processing and cooking

Effects of common processing and cooking methods on sugar and starch contents and starch digestibility (in vitro) of mung bean (Vigna radiata L.) were investigated. Soaking reduced the level of total soluble sugars, reducing sugars, non-reducing sugars and starch and improved starch digestibility, significantly. Cooking (both ordinary and pressure cooking) increased the concentrations of the sugars and digestibility of starch of soaked as well a unsoaked seeds. Starch contents, however, were decreased. Germination decreased starch thereby raising the level of the soluble sugars. Starch digetibility was increased appreciably.     

Effects of variety and nutrient availability on the acrylamide-forming potential of rye grain

Acrylamide is a probable human carcinogen that forms in plant-derived foods when free asparagine and reducing sugars react at high temperatures. The identification of rye varieties with low acrylamide-forming potential or agronomic conditions that produce raw material with low acrylamide precursor concentrations would reduce the acrylamide formed in baked rye foods without the need for additives or potentially costly changes to processes. This work compared five commercial rye varieties grown under a range of fertilisation regimes to investigate the effects of genotype and nutrient (nitrogen and sulphur) availability on the accumulation of acrylamide precursors. A strong correlation was established between the free asparagine concentration of grain and the acrylamide formed upon heating. The five rye varieties accumulated different concentrations of free asparagine in the grain, indicating that there is genetic control of this trait and that variety selection could be useful in reducing acrylamide levels in rye products. High levels of nitrogen fertilisation were found to increase the accumulation of free asparagine, showing that excessive nitrogen application should be avoided in order not to exacerbate the problem of acrylamide formation. This effect of nitrogen was mitigated in two of the varieties by the application of sulphur.     

Modelling the Contribution ofAlpha-Amylase,Beta-Amylase and Limit Dextrinase to Starch Degradation During Mashing

Response surface methodology was used to determine the levels ofalpha-amylase,beta-amylase and limit dextrinase enzymes required for efficient conversion of starch to fermentable sugars during mashing. Micro-scale mashes with purified barley starch and malt enzymes were performed in a Brewing Research Foundation mash bath, and mash liquors were analysed for solubilised starch, reducing sugars (neocuproine assay) and fementable sugars (anion exchange HPLC). Fermentable sugars in the mash liquor were positively correlated with reducing sugars (R²=0·94) and the percentage of starch solubilised during mashing (R²=0·68). A multiple regression equation relating the levels of the three starch degrading enzymes to the percentage of starch hydrolysed to fermentable sugars gave a good fit to the second order response surface (R²=1·00, RMSE=1·37%). Addition of limit dextrinase to the mashes resulted in a substantial increase in levels of fermentable sugars, and limit dextrinase showed a synergistic effect in increasing levels of maltose in the mash liquor when combined with high levels ofbeta-amylase. The efficiency of any one starch degrading enzyme in a mash is influenced by the presence of other starch degrading enzymes. Commercial malts contain excess levels ofbeta-amylase and below optimal levels of limit dextrinase. Malt extract may not be a good indicator of the level of fermentable carbohydrates produced during mashing.     

3个品种香蕉果实中糖酸组分及含量的比较分析

用高效液相色谱(HPLC)法测定皇帝蕉(贡蕉)、巴西蕉和粉蕉成熟果实中糖酸组分及含量。结果表明,成熟果实中均含有蔗糖、葡萄糖和果糖,并以积累蔗糖为主,皇帝蕉(贡蕉)、巴西蕉和粉蕉果实中蔗糖含量分别占总糖的59.76%、66.18%、68.69%,总糖含量大小表现为,皇帝蕉>巴西蕉>粉蕉;均含有11种有机酸,以苹果酸为主,含量分别占总酸的51.71%、47.30%、46.68%,同时含有大量的柠檬酸,分别占总酸的18.13%、19.62%和19.96%,并富含多种有机酸,总酸含量大小是粉蕉>巴西蕉>皇帝蕉。     

Changes in the anti-nutritional factors of developing seeds and pod walls of fenugreek (Trigonella foenum graecum L.)

Anti-nutritional factors of developing seeds and pod walls of fenugreek were evaluated which affect their nutritional value. Sucrose, raffinose and stachyose decreased with maturity of seeds in all the cultivars. Total, non-reducing sugars increased and reducing sugars decreased at maturity in all the cultivars. The reducing sugars decreased with maturity of pod walls. The flatus producing sugars were maximum in PEB pod walls. Saponin content increased towards maturity of seeds but decreased at maturity of seeds and decreased at maturity in pod walls of all cultivars. Phytate increased with seed maturity up to 95 days after anthesis, while phytate decreased in pod walls of all the cultivars with maturity. Total phenol, catechol and flavonol decreased with advancement of pod wall development. Total phenol decreased except HM 46 a maturity of seeds.