Leaf Chlorophyll Readings as an Indicator for Spinach Yield and Nutritional Quality with Different Nitrogen Fertilizer Applications

The objective of this study was to investigate the possibility of predicting the concentrations of total nitrogen (N), nitrate-nitrogen, and ascorbic acid in spinach (Spinacia oleracea) leaves using the pocket chlorophyll meter SPAD-502 (Minolta, Japan) in a pot experiment in a greenhouse. Spinach plants were grown in plastic pots filled with 0.5 kg of brown soil per pot with urea as N fertilizer at 0, 30, 60, 120, and 240 mg N/kg soil. SPAD readings of the two uppermost fully expanded leaves were recorded 18, 25, and 32 d after sowing and at harvesting (34 d). Dry-matter biomass and total N concentrations in leaves and roots, and NO₃-N, and ascorbic acid concentrations in leaves, were measured after harvesting. SPAD readings showed continuous reduction with increasing growth period irrespective of N applications. SPAD readings at harvest were significantly correlated with total N, leaf dry weight (DW), and NO₃-N concentration. However, this correlation did not exist between SPAD readings and ascorbic acid concentrations in leaves. The above results suggest that it is possible to apply SPAD readings to estimate NO₃-N concentrations in spinach plants, and that they may be applied for field assessments in decision-making and operational nutrient-management programs for the plant. Furthermore, the SPAD method may also be useful for ascertaining the harvest time. The results suggest that treatment with 120 mg N/kg significantly improved both leaf yields and leaf quality (i.e., leaf nitrate-N concentration and ascorbic acid). Too little and too much N fertilizer was not good for yield or spinach quality.     

Effect of organic and conventional cropping systems on ascorbic acid, vitamin C, flavonoids, nitrate, and oxalate in 27 varieties of spinach (Spinacia oleracea L.)

This study was undertaken to compare the levels of ascorbic acid, vitamin C, flavonoids, nitrate, and oxalate in 27 spinach varieties grown in certified organic and conventional cropping systems. Liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-(ESI)MS/MS) of methanolic extracts of spinach demonstrated 17 flavonoids, including glucuronides and acylated di- and triglycosides of methylated and methylenedioxyderivatives of 6-oxygenated flavonoids. The mean levels of ascorbic acid and flavonoids were significantly (p < 0.001) higher in the organically grown [40.48 ± 6.16 and 2.83 ± 0.03 mg/kg of fresh weight (FW)] spinach compared to the conventionally grown spinach (25.75 ± 6.12 and 2.27 ± 0.02 mg/kg of FW). Conversely, the mean levels of nitrate were significantly (p < 0.001) higher in the conventionally grown spinach compared to the organically grown spinach. No significant effects were observed in the oxalate content of spinach from either production system. The levels of nitrate correlated negatively with those of ascorbic acid, vitamin C, and total flavonoids and showed a positive correlation with the oxalate content. These results suggest that organic cropping systems result in spinach with lower levels of nitrates and higher levels of flavonoids and ascorbic acid.     

Effects of substrate hydroponic systems and different N and K ratios on yield and quality of tomato fruit

The present study was carried out to determine the influence of wick and drip substrate hydroponic systems and different ratios of nitrogen (N) and potassium (K) in the nutrient solution on fruit yield and quality (titratable acidity, total soluble solids, ascorbic acid, total soluble sugars, firmness, lycopene, carotenoids) in tomato. Summer and winter tomato crop was raised under two substrate hydroponic systems. Four nutrient solutions (N:K ratios in four combinations) were tested in both the growing seasons at vegetative and reproductive stages of plant development. Among the different nutrient solutions, the solution containing N and K in the ratio of 1.4:3 at vegetative and 1.7:3.5 at reproductive stage increased the total fruit yield and quality of tomato irrespective of hydroponic system or season. Among the hydroponic systems, wick system produced higher fruit yield and better quality in terms of firmness, ascorbic acid, and total soluble sugars in winter crop.     

模拟酸雨胁迫对菠菜中草酸积累及营养品质的影响

在田间试验条件下,研究了模拟酸雨胁迫对菠菜中草酸积累及相关营养品质的影响,旨在为优质蔬菜生产提供一定的理论依据。结果表明,经酸雨胁迫处理后菠菜根、叶柄和叶片等器官中草酸的积累量均明显增加,并与酸雨pH值呈显著负相关(r =-0.93*、-0.88*、-0.86*),同对照相比,pH5.0,pH4.0和pH3.0处理增幅分别高达81.2%、147.8%和158.5%;菠菜中蛋白质、游离氨基酸、可溶性糖、Vc等营养成分的含量随着酸雨pH值的减小而逐渐降低,其降幅可分别高达44.98%、64.58%、44.98%和63.23%,不同pH模拟酸雨胁迫下多种营养成分含量的差异达到极显著水平(P< 0.01)。酸雨胁迫会导致菠菜营养及卫生品质劣变。     

Impact of postharvest disease control methods and cold storage on volatiles, color development and fruit quality in ripe 'kensington pride' mangoes

Postharvest diseases of mango fruit (Mangifera indica L.) cause economic losses during storage and can be controlled by chemical, physical, or biological methods. This study investigated the effects of different physical and/or chemical disease control methods on production of volatiles, color development and other quality parameters in ripe 'Kensington Pride' mango fruit. Hard mature green mango fruit were harvested from an orchard located at Carnavon, Western Australia. The fruit were heat-conditioned (8 h at 40 +/- 0.5 degrees C and 83.5 +/- 0.5% RH), dipped in hot water (52 degrees C/10 min), dipped in prochloraz (Sportak 0.55 mL x L(-1)/5 min), dipped in hot prochloraz (Sportak 0.55 mL x L(-1) at 52 degrees C/5 min), dipped in carbendazim (Spin Flo 2 mL x L(-1)/5 min), and dipped in hot carbendazim (Spin Flo 2 mL x L(-1) at 52 degrees C/5 min). Nontreated fruit served as control. Following the treatments, the fruit were air-dried and kept in cold storage (13 +/- 0.5 degrees C) for three weeks before being ripened at 21 +/- 1 degrees C. The ripe pulp of the fruit that was treated with hot prochloraz or carbendazim at ambient and high temperatures showed enhanced concentrations of volatiles, while heat conditioning and hot water dipping did not significantly affect the volatile development. Ripening time, and color development were measured daily while disease incidence and severity, weight loss, firmness, and concentrations of soluble solids, titratable acidity, ascorbic acid, total carotenoids, and volatiles were determined at the eating soft ripe stage. Hot water dipping or fungicide treatments (at ambient or at a high temperature) reduced postharvest diseases incidence and severity. Fruit quality (soluble solids concentration, titratable acidity, ascorbic acid and total caretonoids) was not substantially affected by any of the treatments.     

Thermal degradation of antioxidant micronutrients in citrus juice: kinetics and newly formed compounds

The thermal degradation kinetics of vitamin C, two carotenoids (beta-carotene and beta-cryptoxanthin), and hesperidin, as a function of temperature, were determined for Citrus juice [Citrus sinensis (L.) Osbeck and Citrus clementina Hort. ex Tan]. The influence of dissolved oxygen on the rate of ascorbic acid degradation was also assessed. Analysis of kinetic data suggested a first-order reaction for the degradation of vitamin C and carotenoids. The kinetics parameters Dtheta, z, and Ea have been calculated. Following the Arrhenius relationship, the activation energy of ascorbic acid was 35.9 kJ mol-1 and agreed with the range of literature reported value. The results on vitamin C and carotenoids from citrus juice made it possible to validate the predicting model. Thermal degradation of carotenoids revealed differences in stability among the main provitamin A carotenoids and between these and other carotenoids belonging to the xanthophyll family. The activation energies for the two provitamin A carotenoids were 110 and 156 kJ mol-1 for beta-carotene and beta-cryptoxanthin, respectively. On the other hand, no degradation of hesperidin was observed during thermal treatment. Finally, the vitamin C in citrus juice was not as heat sensitive as expected and the main provitamin A carotenoids present in citrus juice displayed a relative heat stability. The high-performance liquid chromatography-diode array detection-mass spectrometry analysis of degradation products showed that the isomerization of the epoxide function in position 5,6 into a furanoxide function in position 5,8 was a common reaction for several xanthophylls. These findings will help determine optimal processing conditions for minimizing the degradation of important quality factors such as vitamin C and carotenoid in citrus juice.     

Edible coatings influence fruit ripening, quality, and aroma biosynthesis in mango fruit

The effects of different edible coatings on mango fruit ripening and ripe fruit quality parameters including color, firmness, soluble solids concentrations, total acidity, ascorbic acid, total carotenoids, fatty acids, and aroma volatiles were investigated. Hard mature green mango (Mangifera indica L. cv. Kensigton Pride) fruits were coated with aqueous mango carnauba (1:1 v/v), Semperfresh (0.6%), Aloe vera gel (1:1, v/v), or A. vera gel (100%). Untreated fruit served as the control. Following the coating, fruits were allowed to dry at room temperature and packed in soft-board trays to ripen at 21+/-1 degrees C and 55.2+/-11.1% relative humidity until the eating soft stage. Mango carnauba was effective in retarding fruit ripening, retaining fruit firmness, and improving fruit quality attributes including levels of fatty acids and aroma volatiles. Semperfresh and A. vera gel (1:1 or 100%) slightly delayed fruit ripening but reduced fruit aroma volatile development. A. vera gel coating did not exceed the commercial mango carnauba and Semperfresh in retarding fruit ripening and improving aroma volatile biosynthesis.     

Effect of postharvest storage and processing on the antioxidant constituents (flavonoids and vitamin C) of fresh-cut spinach

The effect of modified atmosphere packaging (MAP) and cooking on the flavonoids and vitamin C content (ascorbic + dehydroascorbic acid; AA + DHAA) of fresh-cut spinach was evaluated. The total flavonoid content (approximately 1000 mg kg(-)(1) f.w.) remained quite constant during storage in both air and MAP atmospheres, while vitamin C (750 mg kg(-)(1)f.w.) was better preserved in MAP-stored spinach. AA was transformed to DHAA during storage, and its concentration was higher in MAP-stored tissues. The free-radical scavenging activity of the isolated flavonoids was tested, and only those flavonoids with either a dihydroxyl grouping or acylated with ferulic acid showed significant activity. A decrease in the total antioxidant activity was observed during storage, particularly important in MAP-stored spinach. The higher content of DHAA and lower content of both AA and antioxidant flavonoids in the MAP-stored samples could explain this antioxidant activity decrease. Boiling extracted 50% of total flavonoids and 60% vitamin C in the cooking water. However, flavonoid glucuronides were extracted more in the cooking water than the other glycosides. The vitamin C content of the cooked tissue was higher in those samples stored in MAP.     

Antioxidant capacities,phenolic compounds,carotenoids, and vitamin C contents of nectarine,peach, and plum cultivars from California

Genotypic variation in composition and antioxidant activity was evaluated using 25 cultivars, 5 each of white-flesh nectarines, yellow-flesh nectarines, white-flesh peaches, yellow-flesh peaches, and plums, at the ripe (ready-to-eat) stage. The ranges of total ascorbic acid (vitamin C) (in mg/100 g of fresh weight) were 5-14 (white-flesh nectarines), 6-8 (yellow-flesh nectarines), 6-9 (white-flesh peaches), 4-13 (yellow-flesh peaches), and 3-10 (plums). Total carotenoids concentrations (in microg/100 g of fresh weight) were 7-14 (white-flesh nectarines), 80-186 (yellow-flesh nectarines), 7-20 (white-flesh peaches), 71-210 (yellow-flesh peaches), and 70-260 (plums). Total phenolics (in mg/100 g of fresh weight) were 14-102 (white-flesh nectarines), 18-54 (yellow-flesh nectarines), 28-111 (white-flesh peaches), 21-61 (yellow-flesh peaches), and 42-109 (plums). The contributions of phenolic compounds to antioxidant activity were much greater than those of vitamin C and carotenoids. There was a strong correlation (0.93-0.96) between total phenolics and antioxidant activity of nectarines, peaches, and plums.     

The quality of baby spinach as affected by developmental stage as well as postharvest storage conditions

Baby spinach is rich in phytochemicals that provide great benefits to consumers’ health. The study aim was to investigate the effect of the growth harvest stage, postharvest storage duration and temperature on quality of baby spinach leaves. A 3?×?5?×?3 factorial experiment was laid out in a randomised complete block design with four replicates per treatment. The treatments were arranged as follows namely: stage I [28 days after sowing (DAS)], stage II (35 DAS)and stage III (42 DAS), and leaves were kept up to 12 d at three different temperatures – 4, 10 and 20°C. The study demonstrated that the overall appearance and odour were both well maintained in the leaves of baby spinach harvested at stage II. The baby spinach harvested 28 DAS led to higher content of iron [1.13?mg?g^?1 dry weight (DW)], magnesium (14.4?mg?g^?1 DW), and zinc (0.17?mg?g^?1 DW). The highest level of total antioxidant activity (0.43?mg?g^?1 DW) and flavonoids (12?mg?g^?1 DW) after 12 d of storage was observed in baby spinach leaves at stage I when stored at 4°C. Therefore, baby spinach leaves harvested 28 DAS and store at 4°C for 6 d improved shelf life and nutraceutical quality. Thus, early harvest of fresh produced baby spinach harvested in order to attain high phytochemical and mineral content when stored at low temperature (4°C) without exceeding 6 days is recommended.     

Exogenous applications of salicylic acid affect quality and yield of strawberry grown under antifrost heated greenhouse conditions

Abiotic stress is becoming more prevalent as the intensity of agriculture and the demand for farmable land are ever increasing. Besides drought and salinity stress, chilling or freezing stress is one of the most important limiting factors of crop production all around the world. Salicylic acid (SA) is a common plant‐produced signal molecule that is responsible for inducing resistance to a number of biotic and abiotic stresses. This study was conducted to determine the effect of foliar SA applications on fruit‐quality characteristics and yield of strawberry under antifrost heated greenhouse conditions in two successive experiments. Spraying of 1 mM SA (1 mM) was done once (SA1), twice (SA2), three times (SA3), or four times (SA4) during the vegetation period with 7 d intervals. Concentrations of chlorophyll and minerals were measured in leaves, and vitamin C (ascorbic acid), total soluble solids (TSS), titratable acidity (TA), and color (a*) in fruits. Fruit weight, early yield, and total yield were also determined. Foliar applications of SA positively affected TSS and ascorbic acid (AA) content of strawberry fruits. Salicylic acid treatments had no effect on TA of strawberry fruits. SA4 treatment gave the greatest a* in fruit and chlorophyll‐concentration values in the leaves. It was shown that SA treatments increased the content of all nutrients in the leaves of strawberry plants, and greater values often were obtained from SA3 and SA4 treatments. The early yield and total yield of strawberry were significantly affected by SA applications, among which SA3 and SA4 resulted in the highest early and total yields. The present study suggests that SA3 and SA4 treatments can ameliorate the deleterious effects of low temperatures on strawberry plants and that SA application may offer an economical and simple method for low‐temperature protection.     

Effects of shade regimes and planting geometry on growth,yield and quality of the natural sweetener plant stevia (Stevia rebaudiana Bertoni) in north-western Himalaya

During 2008 and 2009, field experiments were conducted at the research farm of CSIR-Institute of Himalayan Bioresource Technology, Palampur, India to assess the effect of shade levels (no shade, 25% shade, 50% shade, 75% shade) and plant geometry levels [30 × 15 cm (north–south, N–S), 45 × 10 cm (N–S), 30 × 15 cm (east–west, E–W) and 45 × 10 cm (E–W)] on the growth, yield and quality of stevia. Plant development was fastest in controls and slowest in stevia plants growing at minimum light (75% shade). These plants showed delayed bud formation and flowering. Significantly, higher dry leaf yield was recorded when the crop was grown under 25% shading than under 50 and 75% shade. Total steviol glycosides content decreased with increasing shade levels. All shade levels resulted in the same leaf-to-stem ratio, which was significantly higher than that obtained under ambient light. Plant geometry significantly affected the number of leaves and leaf dry weight plant^–1. During both years, dry leaf weight was highest in the wider row spacing (45 × 10 cm) than in the narrow row spacing (30 × 15 cm). Stevia spaced at 30 × 15 cm in an E–W direction recorded significantly higher total steviol glycosides at 2 months after transplanting (MAT).     

香蕉树中度荫蔽下充分灌水提高干热区咖啡产量及品质

为研究香蕉荫蔽栽培下灌溉对干热区小粒咖啡产量和品质的影响,以5 a生小粒咖啡为研究对象,通过大田试验,设3个灌水水平:充分灌水(FI)、轻度亏缺灌水(DIL:75%FI)和重度亏缺灌水(DIS:50%FI),4个荫蔽栽培模式:无荫蔽(S0:单作咖啡)、轻度荫蔽(SL:4行咖啡间作1行香蕉)、中度荫蔽(SM:3行咖啡间作1行香蕉)、重度荫蔽(SS:2行咖啡间作1行香蕉),并运用主成分分析和TOPSIS法对生豆营养品质(总糖、蛋白质、脂肪、咖啡因、绿原酸、粗纤维和水浸出物)进行综合评价。结果表明:小粒咖啡干豆产量受荫蔽栽培模式和灌水水平极显著的影响(P0.01),其中FISM处理的干豆产量最高(5 854.34 kg/hm2),且百粒干质量最大,而该处理的百粒体积和百粒鲜质量与各处理中的最大值相比差异不显著(P0.05)。小粒咖啡大多生豆营养品质在不同荫蔽栽培模式和灌水水平下差异显著(P0.05),蛋白质、脂肪、绿原酸和水浸出物含量间呈极显著正相关(P0.01)。主成分分析法和TOPSIS法均表明,FISS处理的综合品质最优,其次是FISM处理,而DISS0处理的最差。与FIS0相比,FISM处理的产量增加14.32%,而FISS处理减少15.69%。从小粒咖啡提质增产的综合效益考虑,建议干热区小粒咖啡灌水处理和香蕉荫蔽栽培模式的最佳组合选用中度荫蔽栽培下充分灌水,该结果可为干热区小粒咖啡水光管理提供理论依据和实践参考。     

控制光照强度条件下1年生连翘幼苗的生理生态响应

为了调查连翘在发育早期对于不同光照强度条件的生理生态响应和适应性,提高苗期管理质量和出苗率,以1年生连翘幼苗为材料,在人工控制大田环境中设置100%、50%、25%和12.5%4个光照强度水平,通过测量1个生长季后连翘幼苗的存活率、光合生理、地上地下形态、生物量积累和分配等生理生态指标,研究控制光照强度条件下1年生连翘幼苗的生理生态响应。结果表明:1)1年生连翘幼苗在50%光照强度条件下的最大净光合速率、光饱和点和叶绿素b含量显著下降,苗高、地径、总根长、根表面积以及各器官的生物量积累增加显著,根质量比减小,茎质量比和冠根质量比增大;2)在25%光照强度条件下,幼苗的存活率、最大净光合速率、苗高、地径、总根长、根表面积以及各器官的生物量积累增加显著且达到最大值,茎质量比增大;3)在12.5%光照强度条件下,仅最大净光合速率、地径和根系形态指标显著增加,但增幅小于50%和25%光照强度,叶质量比减小。1年生连翘幼苗在光合生理特性上对于遮荫处理表现出不一致的响应,形态和生物量积累在中等光照强度下响应积极一致,且能够通过增加对地上结构生物量的分配比例而适应中等光照强度条件,建议在今后的苗圃培育和管理中应当重视连翘在发育早期的光环境要求。     

Effects of different cooking methods on nutritional and physicochemical characteristics of selected vegetables

The objective of the present study was to evaluate the effect of three common cooking practices (i.e., boiling, steaming, and frying) on phytochemical contents (i.e., polyphenols, carotenoids, glucosinolates, and ascorbic acid), total antioxidant capacities (TAC), as measured by three different analytical assays [Trolox equivalent antioxidant capacity (TEAC), total radical-trapping antioxidant parameter (TRAP), ferric reducing antioxidant power (FRAP)] and physicochemical parameters of three vegetables (carrots, courgettes, and broccoli). Water-cooking treatments better preserved the antioxidant compounds, particularly carotenoids, in all vegetables analyzed and ascorbic acid in carrots and courgettes. Steamed vegetables maintained a better texture quality than boiled ones, whereas boiled vegetables showed limited discoloration. Fried vegetables showed the lowest degree of softening, even though antioxidant compounds were less retained. An overall increase of TEAC, FRAP, and TRAP values was observed in all cooked vegetables, probably because of matrix softening and increased extractability of compounds, which could be partially converted into more antioxidant chemical species. Our findings defy the notion that processed vegetables offer lower nutritional quality and also suggest that for each vegetable a cooking method would be preferred to preserve the nutritional and physicochemical qualities.     

Vitamin C,provitamin A carotenoids,and other carotenoids in high-pressurized orange juice during refrigerated storage

Vitamin C, provitamin A carotenoids, and other carotenoids were measured in freshly squeezed juices from oranges (Citrus sinensis L. var. Valencia late) that were subjected to high-pressure (HP) treatment. Also, the stability of these compounds was studied during refrigerated storage at 4 degrees C. HP treatment is an alternative to heat preservation methods for foods; therefore, it is essential to assess the impact of HP on bioactive compounds. Several processes that combine HP treatment with heat treatment for various time periods were assayed: T0, fresh juice (without treatment); T1, 100 MPa/60 degrees C/5 min; T2, 350 MPa/30 degrees C/2.5 min; T3, 400 MPa/40 degrees C/1 min. Fresh and treated samples were kept refrigerated (4 degrees C) over 10 days. After application of HP and during the refrigeration period, the qualitative and quantitative determination of vitamin C, provitamin A carotenoids (beta- and alpha-carotene; beta- and alpha-cryptoxanthin), and the xanthophylls zeaxanthin and lutein was achieved by high-performance liquid chromatography. T1 and T3 juices showed a decrease in ascorbic acid and total vitamin C just after HP treatment (D0) compared with T0 juices. On the contrary, T2 juices, just after HP treatment (D0), had the same levels of both compounds compared to untreated juices. T1, T2, and T3 treatments led to an increase in the extraction of carotenoids and provitamin A carotenoids. Total carotenoid content after the 10-day refrigerated storage period resulted in no significant quantitative changes in T1 juices, whereas in T2 and T3 juices small losses were found at the end of the storage period (20.56 and 9.16%, respectively). These losses could be influenced by the depleted protection of vitamin C toward carotenoid oxidation during the same period. A similar trend was found in provitamin A carotenoids for the different treated juices.     

Changes in phytochemical and antioxidant activity of selected pepper cultivars (Capsicum species) as influenced by maturity

The effect of fruit maturation on changes in carotenoids, flavonoids, total soluble reducing equivalents, phenolic acids, ascorbic acid, and antioxidant activity (AOX) in different pepper types (Capsicum annuum, Capsicum frutescens, and Capsicum chinese) was determined. Generally, the concentration of these chemical constituents increased as the peppers reached maturity. Peppers contained high levels of L-ascorbic acid and carotenoids at maturity, contributing 124-338% of the RDA for vitamin C and 0.33-336 RE/100 g of provitamin A activity, respectively. Levels of phenolic acids, capxanthin, and zeaxanthin generally increased during maturation, whereas the level of lutein declined. Flavonoid concentrations varied greatly among the pepper types analyzed and were negatively correlated to AOX under the conditions of the beta-carotene-linoleic assay. Model systems were used to aid in understanding the relationship between flavonoids and AOX. Significant increases in AOX were observed in pepper juice models in response to increasing dilution factors and the presence of EDTA, indicating a pro-oxidant effect due to metal ions in the system. In vitro models demonstrated that increasing levels of flavonoids in combination with constant levels of caffeic and ascorbic acid gave a resultant AOX that was either additive of the two compounds or competitive in their ability to scavenge peroxyl radicals. The model systems were in good agreement with the chemical composition of the pepper cultivars and reflected the interactions affecting AOX. More research is needed to understand the complex interactions that occur among various antioxidants present in pepper extracts.     

Spinach-irrigating and fertilizing for optimum quality,quantity, and economy

The increasing scarcity of water for irrigation and environmental pollution due to excessive use of fertilizers are the important problems in vegetable production. A field experiment with combination of three levels of irrigation and nitrogen fertilization was employed to optimize the irrigation and nitrogen fertilizer usage of spinach. Traits, yields, quality, and economic factors of spinach under different regimes were determined. The yield was the highest when spinach was grown under the condition of the soil water content at 16.5% combined with 170 kg ha^?1 of nitrogen fertilizer, while the lowest yield was recorded for the one under the soil water content at 12.5% with 0 kg ha^?1. Nitrate and oxalate contents of spinach were highly dependent on levels of irrigation and nitrogen fertilization. Nitrogen fertilization significantly decreased nitrogen use efficiency. Both water use efficiency and profit responded positively to increased nitrogen fertilizer usage. To optimize the quality and earnings of spinach, and consider the fact that nitrogen fertilizer could degrade the quality of spinach, application of the nitrogen fertilizer at 85 kg ha^?1 and maintenance of the soil water content at 16.5% could be recommended for spinach cultivation under field conditions. Therefore, the findings in this present study are important to improve our knowledge of the irrigation and fertilization for the sustainable agriculture.     

Natural abundance of 15N in nitrate,ureides, and amino acids from plant tissues

The natural ¹⁵N abundances (δ¹⁵N values) were measured for nitrate and free and bound amino acids from the leaves of field-grown spinach (Spinacia oleracea L.) and komatsuna (Brassica campestris L.), as well as ureides and free and bound amino acids in the leaves and roots of hydroponically grown soybean (Glycine max L.) totally depending on dinitrogen. Nitrate from the spinach and komatsuna leaves and ureides from leaves and roots of soybean showed higher δ¹⁵N values than the total tissue N and N in free or bound amino acid fractions. The δ¹⁵N values of individual free and bound amino acids, determined by GC/C/MS using their acetylpropyl derivatives, were similar in leaf tissues except for proline but varied in soybean root tissues. The order of ¹⁵N enrichment was similar in the four samples: aspartic acid > glutamic acid > threonine, proline, valine > glycine + alanine +serine, γ-amino butyric acid, and phenylalanine.     

Bioaccessibility of tocopherols, carotenoids, and ascorbic acid from milk- and soy-based fruit beverages: influence of food matrix and processing

A study was made of the effect of high-pressure processing (HPP) and thermal treatment (TT) on plant bioactive compounds (tocopherols, carotenoids, and ascorbic acid) in 12 fruit juice-milk beverages and of how the food matrix [whole milk (JW), skimmed milk (JS), and soy milk (JSy)] modulates their bioaccessibility (%). HPP (400 MPa/40 °C/5 min) produced a significant decrease in carotenoid and ascorbic acid bioaccessibility in all three beverages and maintained the bioaccessibility of tocopherols in JW and JS while decreasing it in JSy. TT (90 °C/30 s) produced a significant decrease in tocopherol and carotenoid bioaccessibility in all three beverages and increased the bioaccessibility of ascorbic acid. With regard to the food matrix, α-tocopherol and ascorbic acid bioaccessibility was greatest in JW beverages and lowest in JSy beverages, whereas no significant differences were found among the three beverages in terms of carotenoid bioaccessibility. HPP-treated samples showed higher tocopherol and carotenoid bioaccessibility than TT-treated samples, thus indicating that HPP combined with a milk matrix positively modulates the bioaccessibility of certain types of bioactive components of food, mainly those of a lipophilic nature.