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     

The effect of storage on the oxalate content of New Zealand grown oca

Four lines of oca, No. 38 and 41, Inca Gold and Market were grown in four replicated plots and the soluble oxalate content was determined on the freshly harvested tubers and tubers that had been stored for 6 weeks at 16.4 ± 0.5 °C. The mean dry matter content of freshly harvested tubers was 14.3 ± 0.5 g 100 g^?1 fresh weight (FW), and after storage was 14.6 ± 0.5 g 100 g^?1 FW. The mean soluble oxalate content of freshly harvested tubers was 162.1 ± 8.8 mg 100 g^?1 FW, and, after 6 weeks storage, 173.5 ± 0.9 mg 100 g^?1 FW. The different cultivars behaved differently during storage, the soluble oxalate content of Inca Gold tubers fell 7.2% while the soluble oxalate content of the other three cultivars increased (mean 13%).     

Nutritional analysis and sensory evaluation of ulluco (Ullucus tuberosus Loz) grown in New Zealand

Ulluco (Ullucus tuberosus Loz) is an Andean crop that has recently been reintroduced into New Zealand. Nutritional analysis and sensory evaluation were undertaken using standard methods. Ulluco contained high carbohydrate and fibre levels, moderate protein and low fat. Panellists were asked to assess the overall acceptability of raw and cooked ulluco and to state their preferences for colour, bitterness, sweetness and mealiness of cooked ulluco. Red was the most preferred skin and tissue colour of ulluco over plain yellow and mixtures of yellow, green and red. There were no significant differences in panellists' preferences for taste between ulluco cultivars, although panellists disliked the appearance of the multicoloured cultivars. The successful cultivation of this crop in New Zealand in the future will depend on optimising growing conditions and educating consumers about the aesthetic appeal of the different skin and tissue colours. © 2000 Society of Chemical Industry     

Pesticide residues in conventionally grown and organic New Zealand produce

A study was carried out to determine the prevalence and concentrations of pesticide residues in conventionally grown and organic produce (bananas, broccoli, grapes, lettuce, potatoes, tomatoes, wine). Sampling was stratified, with organic produce being over-sampled, when available. All food samples were analysed, as received, by a multi-residue pesticide residue screen. Residues were found in 130 of 307 conventionally grown food samples (42%) and in nine of 41 organic food samples (22%), including six of eleven (55%) organic tomato samples. Only four organic samples (9.8%) contained multiple residues, while 24% of conventionally grown food samples contained multiple residues. Nine conventionally grown food samples (2.6%) contained pesticide residues that exceeded the maximum residue limit (MRL). Where direct comparisons were possible between conventionally grown and organic produce, the mean concentration of residues was usually lower in the organic produce, but was generally higher than would be expected from spray drift or other adventitious sources. While the presence of these residues does not represent a significant risk to human health, their presence is inconsistent with consumer expectations for organic produce.     

Storage of New Zealand Jack Mackerel (Trachurus novaezelandiae) In Ice: Chemical, Microbiological and Sensory Assessment

Physical, sensory, microbiological and chemical analyses were carried out on jack mackerel during 23 days of storage in ice. Sensory results indicate that jack mackerel used in this trial had a shelf-life of 7 days. Aerobic plate counts never exceeded 10⁶/g flesh during the first 11 days. The K value reached 20% after 7 days. Trimethylamine, total volatile base, pH and thiobarbituric acid analyses were not good indicators of changes in quality during the shelf-life. Proximate analyses were carried out on representative samples of the fish.     

Sensory quality and mineral and glycoalkaloid concentrations in organically and conventionally grown redskin potatoes (Solanum tuberosum)

Triangle tests were used to determine if panellists could distinguish (by tasting) cooked wedges of potatoes grown organically, either with (+) or without (?) compost, and conventionally. Mineral and glycoalkaloid analyses of tuber skin and flesh were also completed. When the skin remained on the potatoes, panellists detected differences between conventional potatoes and organic potatoes, regardless of soil treatment. However, they did not distinguish between organic treatments (± compost) when samples contained skin, or between any treatments if wedges were peeled prior to preparation and presentation. Glycoalkaloid levels tended to be higher in organic potatoes. In tuber skin and flesh, potassium, magnesium, phosphorus, sulfur and copper concentrations were also significantly higher in the organic treatments, while iron and manganese concentrations were higher in the skin of conventionally grown potatoes. Copyright © 2005 Society of Chemical Industry     

Identification and stability of trypsin inhibitor isoforms in pea (Pisum sativum L.) cultivars grown in New Zealand

Trypsin inhibitor activity (TIA) of 17 spring-sown field pea cultivars grown in New Zealand ranged from 0.33 to 0.75 TIU/mg DM. These values were much lower than those reported for most European pea cultivars. After soaking and cooking, values fell by 42–91%, with an average reduction of 78% (0.07–0.19 TIU/mg DM). After heat treatment, the residual percentage of TIA was negatively correlated to the amount of TIA in the raw seed. Six to ten trypsin isoinhibitors were observed in each cultivar of the raw extracts, with isoelectric points ranging from 4.6 to 7.6. Only three of the isoinhibitors, with isoelectric points of 5.1, 5.9 and 7.6, remained after heat treatment.     

不同板栗品种(系)抗性淀粉综合评价

对72个板栗品种(系)栗仁中总淀粉、支链淀粉、直链淀粉、抗性淀粉、以及含水量等重要性状分析的测定,为不同板栗品种(系)的利用提供参考。结果表明,不同板栗品种(系)大小、色泽、形状不同;板栗品种(系)中总淀粉的质量分数在51.33%以上,质量分数最高为‘燕秋’,高达71.21%,质量分数最低的是‘波叶-8’,为51.33%;直链淀粉中含量最高的是‘燕秋’,质量分数为18.56%,最低的是‘大兰口’,质量分数为2.43%;支链淀粉含量最高的是‘金丰’,质量分数为58.35%,最低的是‘小官10’,质量分数为35.2%。板栗中含有较高的抗性淀粉。对不同板栗品种(系)中抗性淀粉进行综合评价,抗性淀粉含量最高的品种是‘燕秋’,质量分数为22.2%;最低的是‘徐玉明道’,质量分数为3.44%。通过对不同板栗品种(系)的淀粉进行相关性分析,表明板栗栗仁中直链淀粉与支链淀粉呈极显著负相关,支链淀粉与总淀粉呈极显著正相关,抗性淀粉与直链淀粉呈显著正相关。     

Antioxidant capacity and secondary metabolites in four species of Andean tuber crops: native potato (Solanum sp.), mashua (Tropaeolum tuberosum Ruiz & Pavón), Oca (Oxalis tuberosa Molina) and ulluco (Ullucus tuberosus Caldas)

Four species of edible tubers endemic to and domesticated in the Andes, native potato (Solanum sp.), mashua (Tropaeolum tuberosum Ruiz & Pavón), oca (Oxalis tuberosa Molina) and ulluco (Ullucus tuberosus Caldas), were studied for their antioxidant capacity and associated secondary metabolites. The antioxidant capacity was measured using ABTS^? radicals and total phenolics, carotenoids, anthocyanin, betaxanthin and betacyanin content were also characterized. The antioxidant capacity found in the crops studied ranged from 483 to 9800 µg trolox equiv. g^?1, phenolics ranged from 0.41 to 3.37 mg chlorogenic acid equiv. g^?1, anthocyanins ranged from 0.08 to 2.05 mg cyanidin 3‐glucoside g^?1 and carotenoids ranged from 1 to 25 µg β‐carotene g^?1. The content of bioactive compounds was high and variable between crops and within the genotypes studied. In general, mashua tubers showed the highest antioxidant capacity and phenolic, anthocyanin and carotenoid content compared with other crops. Ulluco was the only crop that contained betalains in the acid form of betaxanthins (22–96 µg g^?1) and betacyanins (64 µg g^?1) with no presence of carotenoids or anthocyanins. This is the first publication regarding the antioxidant capacity of and associated secondary metabolites in Andean tubers. This information can be useful in the identification of Andean tubers species and genotypes with potential value as a novel dietary source of antioxidants for food, and also for medicinal use. Copyright © 2006 Society of Chemical Industry     

Sensory quality of turnip greens and turnip tops grown in northwestern Spain

In Galicia (northwestern Spain), Brassica rapa var. rapa L. includes turnip greens and turnip tops as vegetable products that are characterized by a particular sulfurous aroma, pungent flavor, and a bitter taste. In this work, 12 local varieties grown as turnip greens and turnip tops were evaluated to define the sensory attributes, to relate them with secondary metabolites, and to select those sensorial traits that better describe these crops. Results showed differences in the sensory profiles of B. rapa varieties. Turnip greens were significantly different regarding aroma intensity, leaf color, and salty taste, while turnip tops were for color and firmness of leaves, moistness and fibrosity in mouth, sharpness, and bitter taste. Secondary metabolites as glucosinolates in turnip greens and phenolic compounds in turnip tops were highly correlated with texture and flavor. Glucosinolates, especially progoitrin (in turnip greens) and gluconapin (in turnip tops), showed correlation with bitter taste and aftertaste persistence. Correlation between sensory traits showed highest values between leaf firmness and stalk firmness (R = 0.94**), leaf firmness and fibrosity (R = 0.92**), aftertaste persistence and bitterness (R = 0.91**), and between bitterness and moistness (R = −0.89**).     

A survey of the natural occurrence of Fusarium mycotoxins in cereals grown in New Zealand in 1986-1989.

Fusarium mycotoxins, principally trichothecenes, occurred commonly in grain from crops in the North Island of New Zealand, but were much less common and also at the much lower levels in grains from South Island regions. The principal contaminants were trichothecenes of the nivalenol (NIV) and deoxynivalenol (DON) types. Trichothecenes derived from scirpentriol and T-2 tetraol were not common. Moniliformin occurred very rarely, while zearalenone contamination was not uncommon, but the levels were generally low. Maize kernels were commonly contaminated by moderate levels of both NIV- and DON-type trichothecenes, with levels up to 3.6 mg/kg and 11.95 mg/kg respectively recorded. The occurrence of NIV-type trichothecenes as a general contaminant in the range of 0.3-0.8 mg/kg, and frequently as the main contaminant, is unusual.     

Regional classification of New Zealand red wines using inductively-coupled plasma-mass spectrometry (ICP-MS)

Red wines in a dataset of 120 single-region wines could be classified into seven of the major New Zealand winegrowing regions with an overall accuracy of 80.8% using leave-one-out linear discrimination with the elements Sr, Rb, Ni, Co, Pb, Mn, Cd, Ga and Cs. A higher classification accuracy of 94.4% was achieved when regions were combined into North Island, Nelson, and other South Island regions. The rare earth elements did not prove useful for regional classification, both because of their low and variable concentrations and because their concentrations can be increased upon bentonite fining. Wines originating in the Gimblett Gravels Winegrowing District could be discriminated from wines grown in the remainder of the Hawke's Bay region with a high degree of accuracy using Ba, Cs, Rb, and Pb. A small difference in elemental composition between Pinot Noir, Cabernet Sauvignon, and Merlot wines originating from the Hawke's Bay region was observed. However, despite this difference greater classification accuracy was obtained with a database containing all the red wines than a subset containing only Pinot Noir wines.     

荸荠皮总黄酮的纯化及其抗氧化活性研究

利用大孔吸附树脂纯化荸荠皮总黄酮,探讨总黄酮的纯化条件,并通过总抗氧化性能试验、ABTS试验和DPPH试验评价了总黄酮抗氧化活性。试验结果表明,用乙醇水溶液梯度洗脱D101大孔吸附树脂,获得纯度高、抗氧化活性好的荸荠皮总黄酮,黄酮收率为58.52%,纯度为70.64%。所得总黄酮具有良好的还原能力,为0.60 mmol TE(Trolox当量)/g,和良好的ABTS·+、DPPH自由基清除活性,IC50分别为1.86、0.49 mmol TE/g,其中ABTS·+自由基清除性能均大于对照物Trolox和芦丁,DPPH自由基清除性能大于芦丁。