A comparative study of phenylpropanoid metabolism in gamma irradiated and unirradiated potato tubers

Summary Phenylpropanoid metabolism in gamma irradiated potato tubers was studied by examining the pattern of incorporation of radioactivity from U-¹⁴C phenylalanine into caffeic acid. chlorogenic acid and the coniferyl and sinapyl moieties of lignin. During a post-irradiation period of 21 days a depletion in chlorogenic acid was observed. This is a result of its impaired synthesis as well as an accelerated conversion of chlorogenic acid to ferulic and sinapic acids and their deposition in lignin. The results offer an explanation for the lower level of chlorogenic acid invariably observed in irradiated potato tubers.     

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.     

Rapid bruise development in potatoes with oxygen under pressure

Summary Of a variety of methods tested in connection with the rapid assessment of bruíse susceptibility of potatoes, oxygen under pressure (1. 4 kg/cm²) proved to be particularly effective on the grounds of time saved and authenticity of results. Time required for maximum pigmentation was regularly of the order of 2 h with oxygen compared with 8–12 h with compressed air at the same pressure and a minimum period of 3 days for the controls. From preliminary analysis carried out on the concentrations in potatoes of tyrosine, chlorogenic acid and ascorbic acid, no obvious relationship with susceptibility to bruising could be recognised.     

Potato clone variation in blackspot and soft rot susceptibility,redox potential,ascorbic acid,dry matter and potassium

Tubers of 11 potato clones were compared for susceptibility to blackspot and soft rot, redox potential, ascorbic acid, dry matter, and potassium content. Evaluations were made before and after 6 mo storage at 3.9C. Clonal behavior was generally consistent over 2 yr. Significant differences occurred among clones for each factor except redox potential. Blackspot and soft rot were positively correlated in 5 of 8 comparisons. Neither blackspot nor soft rot was correlated with ascorbic acid or redox potential. Blackspot was positively correlated with dry matter in the fall but not after storage and was negatively correlated with potassium. Soft rot evaluated in air or air plus 8% CO₂ was positively correlated with dry matter in only 2 of 8 comparisons. Soft rot susceptibility did not increase with storage when inoculated discs were incubated in air but did increase when the discs were incubated in air plus 8% CO₂. Ascorbic acid was negatively correlated with redox potential only before storage and decreased to varying degrees in all clones during storage.     

Blackspot pigment development of resistant and susceptibleSolanum Tuberosum L. genotypes at harvest and during storage measured by three methods of evaluation

Blackspot pigment development was measured by three methods: 1) impact, 2) abrasive peeling, and 3) oxidation of tuber homogenates. Genotypes and storage periods were used as variable treatments. All methods were able to separate genotypes based on blackspot resistance although the abrasive peel and homogenization methods provided more consistent results than the impact bruise method. Bruise resistant genotypes transferred their resistance to progeny in crosses with a susceptible genotype which was correlated with tyrosine content. According to the traditional impact bruise technique, tuber resistance to blackspot increased during the eight-to ninemonth storage at 3 C. In contrast, resistance was found to decrease with the homogenization procedure and did not change with the abrasive peel technique. Free tyrosine was consistently associated with blackspot pigment development but chlorogenic acid and caffeic acid were not.     

The involvement of phenolics and phytoalexins in resistance of potato to soft rot

Summary Phenolics, for example chlorogenic, caffeic and ferulic acid, and phytoalexins, such as rishitin and phytuberin, were identified in potato tubers cv. Kufri Chandramukhi. The tissue of healthy tubers contained no detectable phytoalexins but did contain phenolics. The levels of these compounds were correlated with soft rot development. The rotting tissue either was free of these groups of compounds or had low concentrations. The wound periderm formed as a result of recovery from injury and infection contained high levels of the compounds. Much higher concentrations were detected at lower storage temperatures when oxygen supply was adequate. Antibacterial properties of the phenolics identified were tested againstErwinia carotovora which was inhibited by chlorogenic, caffeic and ferulic acids. The three phenolics were more effective together, in proportions in which they occurred in wound periderm, than individually. It was observed that none of these phenolics could inhibit pectolytic enzymes ofE. carotovora.     

Post harvest physiconutritional changes in Kagzi limes (Citrus aurantifolia Swingle) treated with selected oil emulsions and diphenyl

Influence of oil emulsions and diphenyl on post-harvest physico nutritionalchanges in Kagzi limes (Citrus aurantifolia) was studied. During twelvedays of storage, physiological loss in weight (PLW) and rotting were at a minimum in fruits treated with Neem (Azadirachta indica A. Juss.) oilplus diphenyl; juice content was at a maximum in mustard oil + diphenyltreated fruits. With the advancement of storage period, total soluble solidswere increased while ascorbic acid and acidity of fruits decreased. Mustardoil plus diphenyl supported maximum ascorbic acid (25.60 mg/100 ml juice) andminimum total soluble solids (9.03%).     

硫营养对绿茶产量和品质的影响

研究了硫营养对绿茶产量和品质的影响及其可能的机理。试验设2个硫处理(0,50 kg S.ha-1.a-1),每个处理重复4次,完全随机区组设计。结果表明:施硫能够提高产量、增加氨基酸和抗坏血酸(AsA和DAsA)含量,降低茶多酚和酚氨比(TP/AA)。施硫对茶叶品质的改善与降低多酚氧化酶(PPO)的活性、提高硝酸还原酶(NR)和苯丙氨酸解氨酶(PAL)活性有关。     

Effect of processing and storage on the ascorbic acid (vitamin C) content of some pineapple varieties grown in the Rivers State of Nigeria

Ascorbic acid contents of the juice of four different pineapples species grown in the Rivers State of Nigeria were determined before and after storage of whole pineapple and processing and storage of the juice for two months. Ascorbic acid of the fresh juice ranged from 22.5 mg to 33.5 mg/100 g sample. After storage at room temperature (30–32 °C) of whole pineapple for two weeks, ascorbic acid was reduced to between 59 and 65 percent of the fresh juice. Processing the juice by pasteurisation reduced the ascorbic acid to between 28 and 46 percent while storage in plastic bottles for two months further reduced the ascorbic acid content to between 10 and 21 percent.     

Interaction of vitamin C and flavonoids in elderberry (Sambucus nigra L.) during juice processing

A field experiment and two oxidation experiments in the laboratory were carried out. The content of the major anthocyanins, cyanidin-3-glucoside (Cy-3-G) and cyanidin-3-sambubioside (Cy-3-Sa), in the fresh fruits from the 13 cultivars were from 361 to 1266 and from 269 to 656 mg/100 g, respectively. The two minor anthocyanins, cyanidin-3-sambu-bioside-5-glucoside (Cy-3-Sa-5-G) and cyanidin-3,5-diglucoside (Cy-3.5-dG), occurred in concentrations between 5 and 47 mg/100 g. The content of ascorbic acid and quercetin in the fresh fruits of the cultivars varied from 6 to 25, and from 29 to 60 mg/100 g, respectively. Purging of the elderberry juice with N2 and/or addition of ascorbic acid reduced the oxidative degradation rate of the two major anthocyanins and quercetin. Ascorbic acid protected the anthocyanins, but not quercetin from oxidative degradation. Mixing of fruits with air during processing and even a low content of oxygen in the juice before tapping must be avoided by appropriate steps during processing. Improvement of the nutritional value of the elderberry juice and increased protection of anthocyanins against oxidative degradation may potentially be obtained by selection of cultivars with a high content of ascorbic acid.     

Distribution of oxidase enzymes in potato tubers relative to blackspot susceptibility. I. Phenolases

To determine whether phenolase activity is related to susceptibility or resistance to blackspot, tissue from bud and stem ends of potato tubers was assayed for differences in monophenolase and polyphenolase activities, changes in activity due to bruising, and different forms of phenolase. No relationship between blackspot and phenolase activity was found when activities of selected tissue were determined with p-cresol, tyrosine or chlorogenic acid as substrates. A significant positive relationship was found between polyphenolase activity and blackspot susceptibility when total or soluble or particulate fractions of phenolase activity were determined with catechol. Stem tissue had a significantly higher rate of phenolase activity than did bud-end tissue, where activity was determined with p-cresol, tyrosine or catechol; no significant differences in activity between the ends were found when chlorogenic acid was used.     

Effect of home processing and storage on ascorbic acid and β-carotene content of bathua (Chenopodium album) and fenugreek (Trigonella foenum graecum) leaves

The present investigation was conducted to study the effect of selected processing and storage methods on the concentration of ascorbic acid and β-carotene in Bathua and fenugreek, leaves. Methods included storage of leaves with or without polythene bags for 24 and 48 h in a refrigerator at 5°C; at 30°C in polythene bags; drying (sun and oven); blanching (5, 10, 15 min); open pan and pressure cooking. Ascorbic acid content of fresh leaves was 220.97 to 377.65 mg and β-carotene content was 19.00 to 24.64 mg/100 g, DW. The percent loss of ascorbic acid ranged from 2.03 to 8.77 and 45.15 to 66.9 while lower losses (0.0 to 1.75 and 1.63 to 2.84) of β-carotene were observed in leaves, stored in, the refrigerator and at 30°C, respectively. A markedly greater reduction in ascorbic acid and β-carotene was observed in dried, blanched and cooked leaves. The study data suggest that storage of leaves in refrigeration, drying in oven, blanching for a short time and cooking in a pressure cooker results in better retention of these two vitamins.     

Role of oxidative cleavage and acid hydrolysis of oat beta-glucan in modelled beverage conditions

The effects of organic acids (ascorbic, citric and malic acids) associated with beverages were studied in an unpurified oat beta-glucan extract with the purpose of examining the stability of cereal beta-glucan in beverage conditions. Addition of ascorbic acid caused an immediate decrease in viscosity of the extract and the MW of beta-glucan. Citric and malic acid affected moderately and only after a heat treatement. This indicated a dominating role of ascorbic acid induced oxidative cleavage compared to the generally proposed acid hydrolysis of beta-glucan. The nature of ascorbic acid induced cleavage was studied with inhibitors (glucose, mannitol, catalase and phytic acid) and catalysts (Cu- and Fe-ions) of hydroxyl radical attacks. Glucose, mannitol and catalase inhibited and the metals effectively catalysed the viscosity decrease. These indicated that the degradation of beta-glucan in the ascorbic acid treated extract was induced by metal-catalysed hydroxyl radicals. Also, the beta-glucan extract used as a matrix lost its viscosity during storage (+6 °C) concurrently with MW decrease of beta-glucan. When added to the extract, mannitol, glucose and catalase each showed a slight stabilising trend and Fe²⁺-ions caused an immediate decrease in viscosity. The oxidative cleavage appeared to be an important factor to consider in developing novel aqueous beta-glucan enriched products.     

Antioxidant in Mango (<Emphasis Type="Italic">Mangifera indica</Emphasis> L.) Pulp

This work was carried out to investigate the pulp composition of four mango cultivars (Haden, Tommy Atkins and Ubá) at the ripening stage in relation to three components with antioxidant potential (total phenolics, carotenoids and ascorbic acid). Total phenolic compound content was estimated by the Folin-Ciocalteu reagent and total carotenoid content by spectrophotometry at 450 nm. The contents of β-carotene and total vitamin C (ascorbic acid and dehydroascorbic acid) were quantified by high performance liquid chromatography. Differences were found among the four mango cultivars in all the components analyzed. The content of phenolic compounds ranged from 48.40 (Haden) to 208.70 mg/100 g (Ubá); total carotenoid from 1.91 (Haden) to 2.63 mg/100 g (Palmer); β-carotene from 661.27 (Palmer) to 2,220 μg/100 g (Ubá) and total ascorbic acid ranged from 9.79 (Tommy Atkins) to 77.71 mg/100 g (Ubá). These results corroborated previous information that mangoes are a good source of antioxidants in human diet.     

龙眼成花与氧化损伤的关系探讨

以储良龙眼为试材,通过分析低温诱导、氧化胁迫、自然低温+药剂处理龙眼成化过程中氧化损伤各指标变化,研究龙眼成花和氧化胁迫之间的相关性。结果表明,氧化胁迫有利于龙眼成花。对顶芽和叶片活性氧、抗坏血酸和丙二醛(MDA)含量的检测结果也表明,氧化胁迫诱导龙眼成花的同时,也导致了龙眼树各组织活性氧的累积,且抗坏血酸抑制龙眼成花,MDA促进龙眼成花。因此认为活性氧与龙眼成花呈正相关。     

Chemical composition and organoleptic evaluation of juice from steamed cashew apple blended with orange juice

Fully riped cashew apples (yellow variety) were steamed for 7 minutes prior to juice extraction. The extracted juice was blended with various proportions of sweet orange juice. Chemical composition and organoleptic evaluation were carried out on both the blended and unblended juices. The ascorbic acid content of unsteamed cashew apple juice was 287 mg/100 ml. Steaming of the cashew apple prior to juice extraction resulted in a decreased (230 mg/100 ml) content of ascorbic acid. It also led to slight decreases in soluble solids and titratable acidity. A comparison of the chemical composition of the two juices showed that the orange juice contained more sugars, titratable acidity and soluble solids but less ascorbic acid than cashew apple juice. Consequently, the soluble solids, titratable acidity, reducing and total sugars of the blends increased with increase in the proportions of orange juice while the content of ascorbic acid was decreasing. In spite of the decrease in ascorbic acid content of the blends, results showed that blended juice would no doubt be a very good source of ascorbic acid. Result of the organoleptic evaluation revealed that a 60% cashew apple and 40% orange juice gave a good quality juice in terms of flavor, after taste and overall acceptability.     

Photo-induced changes in the concentrations of individual chlorogenic acid isomers in potato (Solanum tuberosum) tubers and their complexation with ferric ions

Summary Changes in the concentrations of 3-, 4- and 5-caffeoylquinic acids in potato tubers exposed to light have been determined by high-performance liquid chromatography. In the first 24 to 48 hours the observed increases in total chlorogenic acid content was due primarily to an increase in 5-caffeoylquinic acid content but thereafter the rate of accumulation of the other isomers increased gradually. After 24 hours exposure 4-caffeoylquinic acid accounted for 10% of the total chlorogenic acid content of the tubers compared with 33% after 168 hours. The significance of this change in isomeric ratio on the spectral characteristics of potential ferrichlorogenic acid complexes was investigated in vitro. It was concluded that potato quality, as reflected in the development of after-cooking blackening, was dependent on total chlorogenic acid content and was unaffected by the relative concentrations of the individual isomers.     

Differences in free and protein-bound tyrosine among potato genotypes and the relationship to internal blackspot resistance

Twelve potato clones were selected to represent the full range of internal blackspot response in order to determine the relationships between tuber protein, free tyrosine, and blackspot susceptibility. The blackspot reaction for each clone was consistent over five growing seasons, including tubers grown over a normal season (mature), and short season (immature) during one year. The blackspot index, determined by either an abrasive peel test or an impact bruise test, was highly correlated with the tyrosine content of the tubers (r = 0.90 p = 0.001 for the means of each clone over five location-years). Tubers with free tyrosine levels below 4 μmole/g dry weight consistently showed a resistant blackspot response. The relationship between tyrosine and blackspot susceptibility was also found in stolon and bud ends from five of the clones which represented the extremes of blackspot reaction and genetic diversity. Bud end samples of each of the clones had lower tyrosine content and a corresponding reduction in blackspot compared with stolon ends. Phenols, other than tyrosine, showed no consistent relationship to the blackspot reaction. There was a very high negative correlation between free tyrosine and estimated protein-bound tyrosine. R values ranged from ?0.85 to ?0.97 (p = 0.001) for mature tubers of the 12 clones over 4 growing seasons. Total tyrosine (free, plus protein-bound) remained relatively constant. There were no significant differences in mean total tyrosine content among the 12 clones over five location-years of testing; and there were no significant differences among the five growing seasons except for the short season (immature) tubers which were 14% lower in total tyrosine content. These results indicate a remarkably constant level of total tyrosine production in the twelve clones studied, that represented diverse genetic backgrounds. Mature tubers of all genotypes contained 26 ± 1 μmole/g dry weight total tyrosine. Partitioning of tyrosine between tuber protein and the free amino acid pool varied with genotype and appeared to be a major determinate of blackspot resistance.     

甘蓝型黑籽和黄籽油菜种子发育过程中种皮色泽差异研究 Ⅱ．黑色素、酪氨酸和酪氨酸酶的变化及相关性

甘蓝型油菜种皮黑色素、酪氨酸酶和游离酪氨酸含量的变化研究结果表明，在种子发育过程中，油菜黑籽与黄籽种皮的黑色素、酪氨酸酶及游离酪氨酸含量差异达极显著水平。种子发育中期，黑籽种皮的黑色素含量逐渐增加，种子成熟时迅速增加，比黄籽增加6倍以上。种子发育后期黄籽种皮的酪氨酸酶活力下降，而黑籽酶活力呈上升趋势。相关分析表明，种皮酪氨酸酶活力与黑色素含量呈显著正相关，与游离酪氨酸含量呈显著负相关，油菜黑籽和黄籽种皮色泽差异与黑色素含量有关，黑色素可能由游离酪氨酸转化而来。     

Nutritional value of potato tubers from field grown plants treated with deltamethrin

Summary Tubers showed changes in their nutritional value caused by the treatment of the plants with the insecticide deltamethrin. The level of starch was increased in comparison with control tubers; but the amylose percentage was not affected. In contrast, the total protein content decreased in tubers from treated plants, whereas free amino acids level and ascorbic acid content increased. The results showed that the changes in the tubers caused by the treatment of potato plants with deltamethrin did not adversely affect the nutritional value of the progeny tubers.