Comparative study of primary and secondary metabolites in apricot (Prunus armeniaca L.) cultivars

BACKGROUND: Apricot is one of the most popular Prunus species grown in the temperate zone and great variation in the contents of primary and secondary metabolites has been reported in its fruit. However, little is known on the phenolic profiles and antioxidant potential of important local cultivars. The objective of the study was to identify valuable parental lines for breeding of cultivars with high health‐promoting effects. RESULTS: Primary metabolites (sugars, organic acids) and secondary metabolites (phenolics) were quantified by high‐performance liquid chromatography–mass spectrometry (HPLC/MS) in fruit of 13 apricot cultivars: total sugars ranged from 59.2 to 212.5 g kg^?1 fresh weight (FW) and total organic acids from 4.2 to 20.8 g kg^?1 FW. Four hydroxycinnamic acids and three flavonols were quantified; their content was significantly higher in skin compared to pulp. Similarly, antioxidative potential was significantly higher in skin and ranged from 125.4 to 726.5 mg ascorbic acid equivalents kg^?1 FW. A positive correlation between total phenolic content and antioxidant potential was determined. Multivariate analysis subdivided the cultivars into five major groups, mostly influenced by the content of individual and total phenolics as well as the antioxidant potential of apricot skin and pulp. CONCLUSION: In regard to high phenolic content in connection with antioxidant potential, three cultivars stand out as the richest in analyzed quality parameters: ‘Mula Sadik’, ‘Bergeron’ and ‘Chuan Zhi Hong’. They also contained high amounts of primary metabolites and should be promoted for further planting and included in apricot breeding programs. Copyright © 2010 Society of Chemical Industry     

Phenolic acids and flavonoids of fig fruit (Ficus carica L.) in the northern Mediterranean region

Phenolics are an important constituent of fruit quality because of their contribution to the taste, colour and nutritional properties of fruit. We have tried to evaluate the phenolic profile of fig fruit, since only limited information on that topic is available in the literature. With the HPLC-PDA system, we have identified the following phenolics: gallic acid, chlorogenic acid, syringic acid, (+)-catechin, (−)-epicatechin and rutin. Phenolics were extracted from three different fig cultivars that are commonly grown in Slovenia’s coastal region. These cultivars were ‘Škofjotka’ (‘Zuccherina’) a white type fruit, ‘?rna petrovka’ and ‘Miljska figa’, both dark type fruit. The fruit from the first and the second crop were collected and compared. In general, fruit from the second crop contained higher values of phenolics than fruit from the first crop. The analysed phenolics present at the highest content were rutin (up to 28.7 mg per 100 g FW), followed by (+)-catechin (up to 4.03 mg per 100 g FW), chlorogenic acid (up to 1.71 mg per 100 g FW), (−)-epicatechin (up to 0.97 mg per 100 g FW), gallic acid (up to 0.38 mg per 100 g FW) and, finally, syringic acid (up to 0.10 mg per 100 g FW). Both cultivars with dark fruit exhibited a higher total level of analysed phenolics, in comparison to the white fruit cultivar ‘Škofjotka’. The amounts measured are comparable to those of other fruits grown in this region. The amounts of rutin in particular are quite high and comparable to apples, for example. As a typical, seasonal fresh fruit, figs can be an important constituent of the regional diet.     

Nutritional Compounds in Figs from the Southern Mediterranean Region

Nutritive value of mature figs (Ficus carica L.) was investigated in five Tunisian cultivars, ‘Bouhouli’ (BHL) and ‘Zidi’ (ZD) (dark skin figs); ‘Thgagli’ (THG), ‘Bidhi’ (BD), and ‘Khedri’ (KHD) (yellow-green skin figs). Sugars, organic acids, fibres, and polyphenols were analysed in representative fruit samples from two distinct regions known to develop fig crops. Tunisian figs were characterized by predominance of glucose (6.30 g/100 g fresh weight) and fructose (5.10 g/100 g fresh weight). Citric acid (0.35 g/100 g fresh weight) was the major organic acid in all cultivars, almost three times higher than malic acid (0.13 g/100 g fresh weight). Average content of alcohol insoluble solids was 3.3 g/100 g FW. Four main polyphenols could be identified: two anthocyanins (cyanidin-3-glucoside; cyanidin-3-rutinoside), one flavonol (rutin), and one hydroxycinnamic acid (5-cafeoylquinic acid), revealed only in ‘BD’ samples. Cyanidin-3-rutinoside was the most abundant compound among all cultivars. Compared to common fruit, figs are among high sugar leveled fruit with significant dietary fibre content. Dark skin ‘ZD’ fruit were the most interesting figs with the highest concentration of sugars, organic acids, and polyphenols, especially cyanidin-3-rutinoside. This cultivar could be better advised for fresh consumption. However, the three lighter cultivars are more suitable for drying.     

FLAVOR AND QUALITY CHANGES IN SWEET ONIONS DURING STORAGE AT ROOM TEMPERATURE

Flavor and quality parameters of onions (Allium cepa ‘Walla Walla Sweet’) were monitored for up to 7 weeks following harvest. Shelf-life of bulbs harvested earlier in the season was shorter than that of onions harvested 3 weeks later. Soluble solids of inner scales and average pyruvate, 3,4-dimethyl thiophene and disulfides content increased during the 4 week shelf-life at 22C of the onions harvested in June. These increases resulted in the final contents to be comparable to those of onions harvested on July 2, 1992, which were relatively stable. The pyruvate concentration was comparable to that of a mild, nonpungent onion. Correlations between pyruvate, thiophene and soluble solids were not significant. The relationship between 3,4-dimethyl thiophene, disulfides and onion flavor is discussed.     

Content of quercetin glycosides and fructooligosaccharides in onion stored in a cold room

In the paper, the authors present the qualitative and quantitative composition of quercetin glycosides and fructooligosaccharides (FOS) in onions commonly grown in Poland of the varieties: Napoleon, Sprinter and Grabowska from the 2006 and 2007 crops, stored in a cold room under standard conditions from October until February. Quercetin glycosides and FOS have been determined using the HPLC method. It has been demonstrated that the mean content of quercetin glycosides in the three varieties of onions from the 2006 and 2007 seasons is 1,381.6 ± 123.1 and 1,479.4 ± 125.5 mg/100 g d.m., respectively, in the edible part, whereby the proportion of quercetin 3-glucoside and quercetin 4′-glucoside amounts to about 60%. In 2006 in the three onion varieties the FOS content was on average 7.0 ± 1.2 g/100 g d.m., while in 2007 it was 6.2 ± 0.9 g/100 g d.m., of the edible part. The content of quercetin glycosides in outer and middle scales of the onions was 3,386.3 ± 190 and 1,017.4 ± 188 mg/100 g d.m., respectively. In the outer scales the FOS content was lower and amounted to 3.1 ± 0.2 g in 100 g d.m., while in the middle scales it was significantly higher 6.8 ± 0.7 g/100 g d.m. The content of quercetin glycosides in onions is high and remains at a constant level during storage; however, since they are found mainly in outer scales, their total removal with a view to obtaining white and milder culinary products results in a loss of approximately half of polyphenols.     

Effects of cultivar,lifting time and nitrogen fertiliser level on quercetin content in onion (Allium cepa L.) at lifting

Commercial cultivars of onion (Allium cepa L.) were grown at Torslunda research station, Sweden with different levels of nitrogen fertiliser and lifted at different growth stages. Soon after lifting, before any drying or curing, tissue from the fleshy edible part of onions was extracted in ethanol and the raw extracts were analysed by high‐performance liquid chromatography without any previous hydrolysis. It was confirmed that the main flavonoid compounds were quercetin monoglucoside and quercetin diglucoside, whereas only trace amounts of quercetin aglycone and other flavonoids were found. The greatest variation in quercetin content, in the range 100–500 mg kg^?1 fresh weight, occurred between years. The concentration of quercetin glucosides in the onions was strongly correlated (R² = 0.98) with the total amount of global radiation in August. Individual onions with fallen leaves had significantly higher concentrations of quercetin glucosides than individuals in the same row with erect leaves. Only minor differences were found between the three cultivars analysed. Higher levels of nitrogen fertiliser had only minor effects on onion yield and size and resulted in lower or equal amounts of quercetin glucosides. Nitrogen leakage from the soil, a potential source of environmental problems, could therefore be minimised by avoiding high nitrogen fertiliser levels with almost no effect on onion flavonol content. Late lifting of onions (80% fallen leaves) resulted in up to 45% higher concentrations of quercetin glucosides compared with early lifting (50% fallen leaves). Copyright © 2006 Society of Chemical Industry     

Bioactive Components and Antioxidant Capacity of Fruits from Nine Sorbus Genotypes

In this study, biochemical profile of fruits of 9 Sorbus genotypes was analyzed. The content of total sugars ranged from 69.7 g/kg (‘Titan’) to 217.5 g/kg (Sorbus torminalis) and total organic acids from 17.7 g/kg (‘Businka’) to 40.2 g/kg (S. torminalis). The highest content of total anthocyanins had ‘Burka’ (871 mg/kg FW) and ‘Businka’ (856 mg/kg FW). Quercetin derivatives represented more than 95% of total flavonols. ‘Alaja krupnaja’ had 3.5‐ to 29‐fold higher rutin content than other analyzed genotypes. S. torminalis fruits had the greatest diversity of isorhamnetin and kaempferol derivatives. Chlorogenic acid was the major hydroxycinnamic acid and its share was 33% to 73% of total analyzed hydoxycinnamic acid derivatives. The richest in chlorogenic acid were ‘Krasavica’ and ‘Alaja krupnaja’ fruits. Cultivar ‘Businka’ had the highest content of epicatechin (40.7 mg/kg) and neochlorogenic acid (1061 mg/kg). Different procyanidin oligomers were detected among flavanols in Sorbus fruits. The highest content of total flavanols was measured in ‘Alaja Krupnaja’ fruits. Cultivars ‘Krasavica’ (84.5 mg/kg) and ‘Burka’ (85.1 mg/kg) had 1.2‐ to 6.9‐fold higher amount of total carotenoids. ‘Businka’ was highlighted as the richest in total tannin and phenolic contents (3768 mg GAE/kg) and consequently, it had the highest antioxidant activity (57.6 mM TE/kg FW). Being abundant in polyphenolics, some extracts of Sorbus genotypes, for example, ‘Businka,’ ‘Burka,’ and ‘Alaja krupnaja’ could serve as valuable resource of bioactive compounds to food and pharmaceutical industries.     

Characterization of Shortday Onion Cultivars of 3 Pungency Levels with Flavor Precursor, Free Amino Acid, Sulfur, and Sugar Contents

ABSTRACT:  This study was conducted to characterize shortday onions of 3 pungency levels with regard to the composition of flavor related compounds. A total of 9 onion breeding lines/cultivars were selected, per each of low, medium, and high pungency level, with pyruvic acid contents of 1.9 to 2.8, 4.8 to 5.4, and 7.2 to 8.3 μmoles/mL, respectively. The contents of flavor precursors (S-1-propenyl-L-cysteine sulfoxide [1-PeCSO] and S-methyl-L-cysteine-sulfoxide [MCSO]), free amino acids, free sugars, soluble solids (SSC), and total sulfur (S) in onion bulbs were measured. The flavor precursor contents ranged from 0.03 to 0.16 mg/g fresh weight (FW) for MCSO, 0.07 to 0.65 mg for 1-PeCSO, and 0.12 to 0.77 mg in total, and precursor contents increased with the pungency levels. Onions of different pungency levels did not differ in the contents of individual or total free amino acids, and the most abundant amino acids were glutamine and arginine. The total sugar contents ranged from 50 to 75 mg/g FW, and total S contents (3.5 to 5.1 mg/g dry weight) were not correlated with the pungency levels. However, pungency levels were correlated inversely with bulb weight and positively with SSC, presumably by the effect of dilution. This study indicates that onion pungency is primarily determined by the content of flavor precursor compounds and not by total S, total sugars, or individual/total free amino acids in shortday bulbs.     

Implications of spatial and temporal changes in concentration of pyruvate and glucose in onion (Allium cepa L.) bulbs during controlled atmosphere storage

BACKGROUND: Pungency and perceived sweetness are important quality assurance parameters for onion producers; however, there is still a paucity of information describing the spatial changes within the bulb of some taste‐related compounds during storage. Accordingly, onion bulbs of cultivars (cvs.), SS1 (low pungency, low dry matter) and Renate (pungent, high dry matter) bulbs, were divided into 12 sections and both spatial and temporal variations of pyruvate and glucose were recorded during standard controlled atmosphere storage. RESULTS: Pyruvate within cv. SS1 bulbs reached 8.3 µmol g^?1 fresh weight (FW) from pre‐storage levels of less than 3.4 µmol g^?1 FW, whilst pyruvate changes in cv. Renate remained in the ‘pungent’ category, between 12 µmol g^?1 FW and 15 µmol g^?1 FW; thus having fewer implications for marketing and quality assurance. Glucose concentrations were significantly higher for both cvs. in the neck region as compared to basal tissue. Higher glucose levels were recorded in the core of the bulb than in outer scales of cv. Renate. The opposite was found for cv. SS1. There was an inverse correlation of ? 0.69 and ? 0.87 between glucose and pyruvate for cvs. SS1 and Renate, respectively. CONCLUSION: In order to measure overall bulb flavour, it is recommended that sampling procedures, particularly for routine pungency determination, be carried out on bulb quarters or wedges rather than equatorial sections. Copyright © 2009 Society of Chemical Industry     

The analysis of flavonoids in staple vegetables and fruits and basic principle of creation of database for estimation of dietary intake of flavonoids by population

The results of analysis of flavonoids (flavonols as rutin) in staple Russian vegetables and fruits are presented. It was shown that onion and apples are the main vegetable and fruit containing the flavonols in considerable amounts of flavonols. The level of flavonols depends on kind of onions. The data are used for creation of database for calculation of dietary intake of flavonoids by Russian population.     

Variability in the content of soluble sugars and cell wall polysaccharides in red‐ripe cherry and high‐pigment tomato cultivars

BACKGROUND: Soluble sugars and cell wall polysaccharides are well known for contributing to a range of ‘quality’ characteristics of fresh vegetables such as flavour, texture and healthy properties. Red‐ripe berries of 14 cultivars of cherry tomatoes and four cultivars of high‐pigment tomato hybrids, cultivated in the south of Italy, were analysed for their content of these important qualitative parameters. RESULTS: Sakura appeared to be the cultivar with the highest amount of soluble sugars (53 g kg^?1 fresh weight (f.w.)), mainly glucose and fructose, and, hence the ‘sweetest’ among cherry tomatoes. High‐pigment tomatoes, especially HLY02 and HLY13, showed a soluble sugar content much lower than cherry tomatoes, as expected for industrial, normal‐size tomatoes. Variations in the fructose/glucose ratio, of between 0.68 and 1.48, were evidenced among the different tomato cultivars. Cell wall polysaccharides isolated from whole fresh red‐ripe berries of each cultivar were analysed chemically. The amount of matrix polysaccharides (0.9–3.4 g kg^?1 f.w.) and cellulose (0.16–1.86 g kg^?1 f.w.), as well as their glycosidic composition, showed significant differences among the different cultivars. Cellulose to matrix polysaccharide ratio was highly variable and ranged between 0.06–1.44 and 0.17–0.77 in cherry and high‐pigment tomato cultivars, respectively. CONCLUSION: The differences evidenced in the total soluble sugar and cell wall polysaccharide composition, not only among different types of tomatoes but also different cultivars within the same typology, may play a fundamental role in the quality of tomatoes and deserve further investigations. Copyright © 2008 Society of Chemical Industry     

Fresh from the Ornamental Garden: Hips of Selected Rose Cultivars Rich in Phytonutrients

Morphological parameters (size, weight, color), the content of sugars, organic acids, lycopene, β‐carotene, and phenolics were determined in hips of Rosa canina (RCA), Rosa sweginzowii (RSW), Rosa rugosa (RUG), and selected ornamental Rosa cultivars Fru Dagmar Hastrup (FDH), Repandia (REP), Veilchenblau (RVB), Aloha (RAL), Bonica (BON), and Golden Gate (RGG). Although traditionally used RCA hips contained the highest amount of cyanidin‐3‐glucoside (83 μg/g DW) and were the reddest (h° = 17.5), they did not stand out in other analyzed parameters. RGG climber had the biggest hips (8.86 g), which also contained highest sugar levels (50.9 g/100 g DW). RAL stood out as the cultivar rich in organic acids (33.9 g/100 g DW), mainly because of high quinic acid content (17.6 g/100g DW). FDH and RSW hips were characterized by particularly high ascorbic acid levels (4325 mg/100 g DW and 4711 mg/100 g DW). Other ornamental cultivars contained low amounts of ascorbic acid compared to the analyzed species. The phenolic profile was species/cultivars‐specific. The greatest diversity of phenolic compounds was detected in RUG and FDH hips (55 and 54 different tentatively identified compounds with HPLC/MS). Flavanols represented the main phenolic class in most of the investigated species/cultivars and RGG hips contained the highest amount of catechin and proanthocyandin derivatives (15855 μg/g DW). Altogether RAL hips contained the highest quantity of phenolics (44746 μg/g DW) mainly due to high levels of hydrolysable tannins compared to other species/cultivars. Although small, hips of BON and REP were most abundant regarding β‐carotene and lycopene content, respectively.     

Assessment of the flavour of fresh uncooked onions by taste‐panels and analysis of flavour precursors,pyruvate and sugars

Flavour in fresh onions is dominated by volatile sulphenic and thiosulphenic acids that are liberated once alk(en)yl cysteine sulphoxide (ACSO) flavour precursors are cleaved by the enzyme alliinase after tissue disruption. The levels of pyruvate and ACSOs in over 100 samples of onions marketed in the UK were measured, and compared with assessment by taste‐panels. There was a linear relationship between the content of ACSOs and pyruvate. Measurements of pyruvate indicated that the marketing classification of some types of onion did not correspond to their pyruvate levels. A significant linear relationship was found between a sensory measure of strength and pyruvate over the range 1.2–9.3 µmol pyruvate g^?1 fresh weight. In most cases, when a flavour classification of sweet, mild or strong was applied to a sample of onions based on pyruvate content, the taste‐panels agreed with the categorization. The taste‐panels were unable to identify a sweet flavour in onions, except at low levels of pyruvate. Taste‐panels were able to define a likeability character (attractiveness of flavour) for onions, which correlated with the level of pyruvate. However, for some varieties, the flavour classification or likeability did not correspond to predictions based on pyruvate levels alone. Pyruvate measurements were seen as a suitable method for routine quality control once the characteristics of a variety of onion had been established, but initial evaluations should include well‐designed taste‐panel assessments. Copyright © 2004 Society of Chemical Industry     

Distribution of quercetin-3,4′-O-diglucoside,quercetin-4′-O-monoglucoside,and quercetin in different parts of the onion bulb (Allium cepa L.) influenced by genotype

Flavonoids have gained much attention because of their proposed positive effects for human health. Onions are a rich source of flavonoids, consisting mainly of the major flavonols quercetin-3,4′-O-diglucoside (QDG) and quercetin-4′-O-monoglucoside (QMG) in the bulb and the aglycone quercetin in the outer scales. In this study, distribution of these three flavonoids was determined in 16 onion cultivars (Allium cepa) using HPLC–DAD. Three different parts of the onion bulb, the inner layers, the middle layers and the outer scales were analysed. The analysis showed varietal differences in the selected onion cultivars. The cultivars with the highest total flavonoid content were the red skinned ‘Red Baron’ and the yellow skinned cultivars ‘Ailsa Craig’ and ‘Prilep’. The distribution of the total flavonoid content in the different parts of the onion bulb showed the following order: middle layers > outer scales > inner layers. In the inner layers QDG was the major flavonoid, while in the middle layers QDG and QMG were in equal amounts. In the outer scales quercetin was the major flavonoid prior to QMG.     

百香果果汁营养特性分析与评价

本研究分析了我国百香果主栽品种的果汁营养成分,采用固相微萃取结合气相色谱-质谱联用法（HS-SPME -GC-MS）分析其香气成分,并利用主成分因子分析（principal component analysis,PCA）对四个鲜食百香果品种的营养品质特性进行综合评价。结果表明,四种百香果果汁的营养成分存在明显差异,黄果品种‘大黄金’和‘芭乐黄金果’的可溶性糖、糖酸比、维生素C、矿物质元素及氨基酸含量等明显高于紫红果品种‘台农一号’和‘满天星’。百香果果汁中氨基酸总量为1113.2～1238.9 mg/100 g,其中谷氨酸含量最大（204.00～256.00 mg/100 g）,占总氨基酸比例为19.93%,天门冬氨酸次之,蛋氨酸（0.53%）和胱氨酸（0.26%）的含量最低。鉴定出四种百香果果汁中含有153种香气成分,其中四个品种共有成分为23种物质;香气物质中以酯类为主（80.02%）、醇类、萜烯类和酮类次之,醛类、酸类、烷类等含量较低,其中酯类以己酸乙酯、丁酸乙酯、己基丁酸酯和己酸己酯等为主。以所测17个指标作变量进行主成分因子分析,结果显示,‘大黄金’作为鲜食百香果综合内在品质得分最高,其他依次为‘芭乐黄金果’、‘满天星’和‘台农一号’。本研究为百香果育种与加工提供了理论指导。     

Norwegian‐grown Jerusalem artichoke (Helianthus tuberosus L.): morphology and content of sugars and fructo‐oligosaccharides in stems and tubers

BACKGROUND: Two field trials growing Jerusalem artichoke (Helianthus tuberosus L.) are discussed. Twenty genetic variants were compared in order to find genotypes suitable for Norwegian production. A second trial investigated the above‐ground part of early and late variants. RESULTS: The highest yield (28.7 t ha^?1) and highest amount of tubers per plant was obtained in early variants, e.g. the white Tysnes gave 1.72 kg tubers plant^?1. Early variants had a markedly lower portion of smooth tubers. Late variants gave the most preferable tuber shape, but low yield. Only a weak correlation was found between dry matter content and total content of fructo‐oligosaccharides (FOS) (r = 0.255) in the tubers. The mean content of FOS including sucrose through all variants was found to be 116 g kg^?1 fresh weight (FW) or 550 g kg^?1 dry weight (DW). The average chain length of FOS in the tubers was found to be DP3.9. There was no difference in tuber FOS content between early and late variants. The highest above‐ground amount biomass was found for the late variants when harvested in September. The content of soluble carbohydrates was found to be highest in stalks in August (sucrose and FOS major compounds). CONCLUSION: Early variants give the highest tuber yield under Norwegian growing conditions. Late variants give highest above‐ground biomass. Copyright © 2010 Society of Chemical Industry     

Genetic and environmental effects on levels of glycoalkaloids in cultivars of potato (Solanum tuberosum L.)

Glycoalkaloids were assayed in fifty-five potato cultivars, fifty-four breeding lines and one other species (S. stolonifer). The total glycoalkaloid content ranged from 16·3 μg/g FW for Alpha to 317·0 μg/g FW for Berita, with most values lying between 35 and 65 μg/g. The α-solanine content, as a percentage of total glycoalkaloids, ranged from 28·3% for Avenir to 57·0% for H42, with the majority of values lying between 38% and 46% α-solanine. There was a highly significant correlation between high total glycoalkaloid content and per cent α-solanine (P < 1%). The presence of β₂-chaconine was also related in a highly significant way to high total glycoalkaloid content. Potatoes grown at Yanco (hot, dry, inland climate) contained more glycoalkaloids (～60%) than when grown at Glen Innes (cooler, high altitude climate). However, there was no significant difference between total and relative glycoalkaloid levels of cultivars grown at Glen Innes and Healesville (coastal, temperate climate). A significantly higher per cent α-solanine content, but not total glycoalkaloid content, was observed for potatoes grown in the second year at Glen Innes.     

Non-structural carbohydrates in processed soft fried onion (<Emphasis Type="Italic">Allium cepa</Emphasis> L.)

The effects of curing, removal of top and root, peeling, storage of raw and peeled onion on the content of non-structural carbohydrates and the ability of onion to develop a brown colour were studied. Glucose, fructose, sucrose, 1-kestose, neokestose, nystose, 1^F--d-fructofuranosylnystose and four unknown oligofructosides were quantified using high performance anion exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD). Field drying affected the concentration of fructose only. Glucose, fructose and an unknown fructan decreased in concentration while the concentration of, e.g. 1-kestose, neokestose and nystose increased by removal of root and top of the onions when stored at 15 °C for one week. Peeling had minor influence on changes in non-structural carbohydrates. Storage of non-peeled (raw) onions at 5 °C and storage of mechanically damaged and peeled onion at 20 °C promoted fructan hydrolysis and browning of soft fried onion. Similar changes were produced by long-term storage of cultivars of common onion. Dry matter and fructose increased during storage of peeled onions at both 5 and 20 °C. The increase in fructose content during storage was due to a significantly decrease in the content of 1-kestose, neokestose, 1^F--d-fructofuranosylnystose, an unknown fructan and total fructans. It was concluded that the missing ability of industrially processed onions to develop a brown colour may be overcome by storage of the peeled onions for a few hours or even overnight at 5 °C.     

‘安哥诺’李5℃冷藏期间果肉抗氧化能力的变化

为研究‘安哥诺’李5℃冷藏期间果肉抗氧化能力的变化,以‘安哥诺’李果实为材料,5℃下冷藏50d,使用分光光度计法测定果肉中的花青素、类黄酮、总酚含量、DPPH自由基清除率与抗氧化酶(POD、SOD、CAT)活性。结果表明:5℃冷藏期间‘安哥诺’李果肉的花青素、类黄酮含量均迅速上升且均在第50天时最高,依次为4.52 U/g FW和1.969 U/g FW;总酚含量变化不显著,DPPH自由基清除率先下降后上升;POD活性缓慢下降,SOD活性上升,冷藏30 d和50 d时显著高于冷藏0 d;CAT活性呈上升趋势,冷藏50 d时最高,为10.15 U/(g FW·min)。‘安哥诺’李5℃冷藏50 d期间果肉中花青素和类黄酮含量上升,SOD和CAT酶活性增加,抗氧化能力增强。     

The effect of cooking on the location and concentration of oxalate in three cultivars of New Zealand‐grown oca (Oxalis tuberosa Mol)

Oca (Oxalis tuberosa Mol) originates from South America but is now also grown commercially in New Zealand. It contains moderate amounts of oxalate, which is only present in its soluble form. The skin of the oca tuber is thought to contain more oxalate than the flesh. In this study the concentration of soluble oxalate was measured in the skin and outer and inner flesh and in the whole tuber of raw, boiled, baked and steamed oca. The analysis was carried out on the traditionally pinkish‐red New Zealand cultivar and on the newly introduced cultivars ‘Mellow Yellow’ and ‘Apricot Delight’. In the raw oca tuber the oxalate concentration in the skin is significantly higher than in the flesh (mean value 7.3 g kg^?1 fresh weight (FW) compared to 1.7 and 1.4 g kg^?1 FW in the outer and inner flesh respectively). The highest concentration was found in the skin of the pinkish‐red cultivar (10.9 ± 1.0 g kg^?1 FW). All cooking methods seemed to cause a migration of oxalate from the skin to the underlying flesh. On a fresh weight basis, baking significantly increased the oxalate concentration in the whole tuber, whereas boiling decreased the concentration and steaming had no significant effect (p < 0.001). Boiling might therefore be a better way of cooking oca than baking when a low intake of oxalate is desired. © 2001 Society of Chemical Industry