Greenhouse climate control affects postharvest tomato quality

In this study, important quality properties such as firmness, sugar and acid levels were measured and analysed in tomatoes harvested from three greenhouses during a five month period and stored at 16 °C for over 20 days. Tomatoes were harvested from three identical, neighbouring, greenhouses which were either conventionally ventilated (open greenhouse) or mechanically cooled (semi-closed greenhouses). Sugar and acids levels were hardly affected by greenhouse type. Compared to the open greenhouse, semi-closed greenhouses produced heavier and less mature (firmer) fruit at the commercial harvesting stage based on colour. Fruit maturity differences could be linked to the vertical temperature gradient and to CO₂ levels in the different greenhouses. This indicates that CO₂ levels and temperature affect the synchronisation between colour and firmness maturity at harvest. The acceptance period, i.e., the time period both tomato colour and firmness are considered acceptable by consumers, will likely be positively affected when growers switch from conventionally ventilated to semi-closed production systems. Additional to greenhouse effects also effects of the harvest month were observed. The sugar to acid ratio was highest and glucose to fructose ratio was lowest in July, the month with the highest irradiance, irrespective of greenhouse type. The estimated value for the maximum firmness (F_max) varied from 17.9 N in August to 31.2 N in June. This monthly variation in F_max explains an important part of the variation found in the postharvest behaviour of tomatoes. Interestingly, the monthly variation in F_max showed the same trend as found for the monthly initial sugar levels. It might be hypothesised that the monthly variation in glucose and fructose levels causes variation in that part of firmness that is generated by cell turgor. The monthly variation in F_max, sugar and acid levels could not be linked to climate conditions and remains to be elucidated.     

Gas chromatographic analysis of monosaccharides in a forest soil profile: Analysis by gas chromatography after trifluoroacetic acid hydrolysis and reduction-acetylation

The analysis of sugars in soil at a molecular level may help to understand their origin and function. Gas chromatographic determination of individual sugars was applied to the litter layers and all mineral soil horizons of an acid forest soil under broad-leaved trees. Hydrolysis was carried out using trifluoroacetic acid (TFA). For GC analysis, the monosaccharide units were derivatised by reduction to alditols and subsequent acetylation. The results indicate a strong contribution of microbial-derived carbohydrates in the mineral soil (Ah to Cv horizons) compared to the litter layers (L, Of and Oh horizons).     

Evolution of Carbohydrates of Pre-Cut Mango Slices Subjected to Osmotic Dehydration

Haden mango slices (non-osmotic dehydrated, NOD) were immersed in calcium chloride (2 g/l), citric acid (5 g/l), hydrogen peroxide (25 ml/l) and sodium benzoate (20 g/l) solutions. Slices to be treated with osmotic dehydration (OD) were first immersed in calcium, then placed in the osmotic solution (sucrose 65 ^∘Bx, 30 ^∘C) and 211 mbar vacuum was applied for 30 min. After the osmotic treatment, the slices were immersed in the same solutions as for NOD slices. All the slices were stored in sterile chambers at 24, 13 or 5 ^∘C. Both OD and NOD slices displayed sucrose synthesis (SS) during storage, which was highest in NOD slices that were kept at 13 ^∘C. Sucrose synthesis was the most significant change during ripening of whole mangoes (WM). Starch breakdown could not supply the necessary substrates for sucrose synthesis in either whole mangoes or slices. Injured tissues from mango slices sustained sucrose synthesis, which was highest at 13 ^∘C in NOD slices, but the osmotic treatment decreased sucrose formation. Storage at 5 ^∘C for 12 days affected sucrose content of Haden mangoes. Glucose and fructose concentrations remained low in all treatments.     

Effect of gamma irradiation on the physico-mechanical and chemical properties of potato (Solanum tuberosum L.), cv. ‘Kufri Sindhuri’, in non-refrigerated storage conditions

The effects of γ-irradiation doses, 0.04, 0.08, 0.12 and 1 kGy, applied at two different postharvest times (5 and 30 days after harvest), were studied on the textural behaviour (puncture force, shear force, work done to puncture and shear, cohesiveness and gumminess), microstructure, reducing sugar, total sugar and tuber losses of potato (Solanum tuberosum L.), cv. ‘Kufri Sindhuri’, during storage at 22 °C (RH: 85–90%). The lowest dose (0.04 kGy) was sufficient to inhibit sprouting in potatoes exposed on day 5 but not in the tubers exposed on day 30. The irradiated, non-sprouted potatoes maintained their appearance during storage. Potatoes irradiated early appeared more sensitive to radiation-induced damage, resulting in excessive loss of tubers at 1 kGy but low doses (up to 0.12 kGy) did not increase the susceptibility of the tubers to rotting. No significant differences between reducing sugar and total sugar contents of the control and low dose irradiated tubers were observed after 120 d. High dose (1 kGy) induced blackening of the bud tissue, increased rotting percentage and poor textural quality. Increasing low doses (up to 0.12 kGy) progressively reduced the textural deterioration in the tubers during storage. The scanning electron micrographs of potatoes irradiated with 0.08–0.12 kGy showed intact cells with rigid cell walls, accounting for the higher textural values registered by the samples. Among the two treatment timings, ‘K. Sindhuri’ irradiated early after harvest (i.e., on day 5) with 0.08–0.12 kGy doses retained higher textural parameters compared to those irradiated after a delay (day 30). The study showed the potential effect of γ-irradiation for enhancing the storage life of potatoes in non-refrigerated storage.     

苹果中蔗糖,葡萄糖,果糖,苹果酸的非破坏检测

探讨了用近红外光谱法非破坏检测苹果中糖、酸等四种组分的可行性，采用二阶导数来处理光学数据，分别筛选出９１４ｎｍ、９５０ｎｍ、８９７ｎｍ、９１２ｎｍ代表苹果中蔗糖，葡萄糖，果糖，苹果酸的第一特征波长。经多元线性回归分析，与高效液相色谱法相比，其复相关系数分别为０．９９７、０．９９２、０．９９２、０．９９６。对３２个预测样品的检验误差为０．０８５、０．０５７、０．１７８和０．０２１。结果表明近红外光谱     

The determination of sugars in tomato fruit: A comparison of volumetric,automated colorimetric and gas chromatographic methods

Abstract

Fifty samples of tomato fruit have been analysed for sugars using a reliable but laborious volumetric method and the results compared with those obtained both by a rapid automated colorimetric procedure employing the Technicon AutoAnalyzer and by a gas Chromatographic (GLC) technique. Using cleared fruit extracts, the overall mean results for the volumetric and automated methods were not significantly different. Automated analysis of uncleared extracts gave only slightly lower results and in view of its speed this method is recommended for the rapid routine analysis of tomato fruit. The GLC procedure gave results some 4% lower than those for cleared extracts by the other methods, but this technique has the advantage that the concentrations of the individual sugars (glucose and fructose) are readily obtained if required.     

检测草莓果中多组分的新方法——近红外光谱法

用近红外光谱法（ＮＩＲｓ）分析草莓中的蔗糖、葡萄糖、果糖、柠檬酸、苹果酸和维生素Ｃ等６种成分，与高效液相色谱法（ＨＰＬＣ）有测值相比较，其相关系数分别为０．９９２０、０．９９１４、０．９８８８．０．９９５４．０。９９４９和０．９９８０，标准误差为０．０２１、０．０３５、０．０６５、０．０４４、０．０２９．０。７２７。说明ＮＩＲｓ法与ＨＰＬＣ法的准确度相似。由于此法具有快速、非破坏、样品不需要预处理     

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.     

Changes in oil,sugars and nitrogenous components during germination of sunflower seeds,Helianthus annuus

Since germination has been found to improve the nutritional quality of grains, sunflower seeds Helianthus annuus were germinated for up to five days, and the cotyledons were analyzed for oil, sugar, free amino acid, non-protein nitrogen, lysine, tryptophan and methionine contents. Protein was fractionated. Soaking and germination increased the non-protein nitrogen, total free amino acid, lysine and tryptophan contents. Protein content and dry weight decreased. The oil content decreased significantly after 72 hours of germination. The reducing sugars increased gradually until day five of germination.The saline soluble albumin and globulin fractions decreased while the glutelin content increased during germination. No changes were noticed in the prolamin and methionine contents.     

Concentration of sugars, phenolic acids, and amino acids in forest soils exposed to elevated atmospheric CO2 and O3

Concentrations of soluble soil sugars, soluble phenolic acids, and free amino acids were measured in three forest communities at the FACTS-II Aspen FACE Site near Rhinelander, WI, in order to better understand how elevated atmospheric CO₂ and O₃ are influencing soil nutrient availability and cycling. Sugars, phenolic acids, and amino acids are mostly derived from plant and microbial processes, and have the potential to be influenced by changes in carbon inputs. We hypothesized that concentrations in the soil would parallel increases seen in biological activity, due to greater net primary productivity under elevated CO₂ and seasonal patterns of root growth. Chemical analysis of soils revealed marginally significant increases of total soluble sugars and total soluble phenolic acids in the elevated CO₂ treatment (+27 mg kg⁻¹, +0.02 μmol g⁻¹), but there were no significant differences in concentrations due to elevated O₃ or CO₂+O₃. Total free amino acid concentrations were not affected by any of the treatments, but significant shifts in individual amino acids were observed. Elevated CO₂ and the interaction treatment (elevated CO₂+O₃) increased aspartic acid concentrations, while elevated O₃ treatment decreased the concentration of valine. Concentrations of sugars increased throughout the growing season, while phenolic acids were constant and amino acids decreased. The birch-aspen community had the highest concentration of phenolic acids and sugars overall, while maple-aspen had the lowest. These findings suggest that concentrations of soluble sugars, soluble phenolic acids, and free amino acids in the soil are strongly influenced by soil properties, plant and microbial activity, plant community composition, and to a lesser degree, changes in atmospheric CO₂ and O₃.