Effect of post‐harvest treatments on the level of glucosinolates in broccoli

Broccoli is a very perishable vegetable with a high water content (around 88%) which leads to rapid dehydration and probably to an alteration in composition if conditions after harvest are not controlled. This study evaluates the glucosinolate pattern and glucosinolate levels in the principal and secondary inflorescences of fresh broccoli cv ‘Tokyodome’, and after being submitted to some situations which are likely to occur during or after harvest: room temperature (±20 °C) for 5 days, kept in the fridge at 4 °C for 5 days, and frozen after blanching. Another set of material was harvested 5 days later, simulating a post‐maturation stage, and analysed. The highest total glucosinolate content was found at commercial maturation with 20 888 and 20 355 µmoles kg⁻¹ DW in the principal and secondary inflorescences, respectively. Keeping the inflorescences at room temperature caused the most significant (P < 0.05) reductions in total and individual glucosinolates, except for 4‐hydroxyindol‐3‐ylmethyl‐, 2‐hydroxy‐2‐phenylethyl‐ and 2‐phenylethyl‐, when compared to the other situations. The highest levels (10 925 µmoles kg⁻¹ DW) of 4‐methylsulphinylbutyl‐, the precursor of the anti‐cancer isothiocyanate sulphoraphane, were found in the inflorescences freshly harvested at commercial stage. Refrigeration at 4 °C and freezing were shown to be the best preservation processes for maintaining high levels of these and other glucosinolates in contrast with the other situations. © 1999 Society of Chemical Industry     

不同干燥方法对提取羽衣甘蓝中叶黄素的影响

本试验利用柱层析法测定了不同干燥处理方法羽衣甘蓝叶片中叶黄素的含量.实验结果表明,将真空冻干技术用于羽衣甘蓝叶黄素的提取,可有效提高提取率.     

大孔吸附树脂纯化西兰花色素的研究

目的:筛选对西兰花色素具有良好选择性的大孔树脂,并研究其动态吸附与解析性能。方法:通过静态吸附特性研究,以吸附率和解析率为指标,从5种不同型号的大孔吸附树脂中筛选出对西兰花色素选择性好的树脂,再进而考察各种工艺参数对树脂吸附及洗脱的影响。结果:AB-8对西兰花色素具有良好的选择性,静态及动态吸附及解析特性研究显示其最佳的纯化工艺参数为:上样液浓度2.5mg/mL、流速1.0mL/min、pH4.0、温度50℃;洗脱液采用体积分数80%的乙醇、流速1.0mL/min。采用此工艺条件,西兰花色素色价从23.7提高到91.7。结论:AB-8型大孔树脂对西兰花色素具有良好的吸附与解析性能,适用于西兰花色素的纯化。      

花椰菜不同品种类型间营养成分差异及烹饪对其含量的影响

为探明花椰菜不同品种类型间营养成分及抗氧化活性差异及烹饪对其影响,采集白花菜、松花菜、青花菜以及罗马花椰菜四种花椰菜样品,检测其维生素C、总胡萝卜素、总黄酮、总酚等营养成分含量及其抗氧化活性,并研究水煮、蒸制、微波及清炒烹饪过程对其营养成分含量的影响。结果表明:花椰菜不同品种类型间营养成分及抗氧化活性具有较大差异,其中罗马花椰菜中维生素C、总胡萝卜素及总黄酮含量最高,分别为75.67 mg/100 g、39.24 μg/100 g以及4.34 mg RE/100 g。青花菜总酚含量最高,为38.04 mg GAE/100 g,总胡萝卜素及总黄酮含量仅次于罗马花椰菜,松花菜除总酚含量低于白花菜外,其它均高于白花菜;青花菜的DPPH及ABTS自由基清除能力均为最高,分别为68.40%和28.00%,罗马花椰菜次之,而白花菜和松花菜的FRAP还原能力较高,且二者差异不显著(P>0.05)。烹饪处理花椰菜对其营养成分及抗氧化活性具有不同影响,维生素C含量不同程度损失,总胡萝卜素既有损失又有提升,总黄酮和总酚含量整体为提升,DPPH及ABTS自由基清除能力提升,FRAP还原能力下降。不同烹饪处理中蒸制方式对于花椰菜营养成分及抗氧化活性保持或提升作用较好,其次为微波、水煮及清炒。本实验获得的花椰菜不同品种类型营养成分及抗氧化活性特点可为特定人群花椰菜消费以及烹饪方式选择提供依据,同时亦可为居民通过花椰菜饮食营养物质摄入风险评估提供基础数据。     

Influence of light on health‐promoting phytochemicals of broccoli sprouts

BACKGROUND: Broccoli (Brassicaceae) is a rich source of phytochemicals (glucosinolates and phenolic compounds) and micronutrients (vitamins and minerals). Germinated broccoli sprouts contain much higher levels (10–100 times) of aliphatic (glucoraphanin) and indolic glucosinolates than the inflorescences. This quality characteristic of broccoli sprouts plays an important role in human health and disease prevention. Although it is known that genetic and environmental factors can affect the composition of broccoli inflorescences, the influence of such factors on the seeds and sprouts has not been widely reported. Therefore the aim of this study was to determine the effect of light versus dark growth conditions on the phytochemical composition (vitamin C, phenolic compounds and glucosinolates) of broccoli sprouts. RESULTS: Broccoli sprouts grown in the light were found to have much higher concentrations of vitamin C (by 83%), glucosinolates (by 33%) and phenolic compounds (by 61%) than those grown in the dark. During a 7 day period there was a clear and analogous trend in both treatments, with a general reduction in concentrations over time. Among the different organs studied (seeds, cotyledons, stems and roots), the cotyledons contained the highest levels of bioactive compounds, while the roots contained the lowest. CONCLUSION: Light treatment of sprouting broccoli seeds increased their concentration of health‐promoting phytochemicals, mainly during the first 3–5 days of development. Therefore the younger broccoli sprouts are a better source of bioactive compounds for the consumer than the inflorescences. Copyright © 2008 Society of Chemical Industry     

Effect of pretreatment with salt and sucrose on the quality and stability of dehydrated cauliflower

Dehydrated cauliflower was prepared by soaking the blanched pieces in solutions of different concentrations of common salt and sucrose (cane sugar), alone and in combination, prior to drying in a cabinet drier and evaluated for sensory, rehydration, storage, microbiological, histological and sorption characteristics. While sucrose alone produced considerable improvement, salt supplemented its effect. The optimum treatment was soaking in 3% salt and 6% sucrose for 12–16h at 4°C it markedly reduced shrinkage and improved rehydration without affecting palatability. It was necessary to boil the soak solution for 3 min and cool prior to soaking to reduce microbial contamination. The treatment increased ascorbic acid loss by 8%. Monolayer moisture content calculated from BET equation was 6.5% (moisture-free) basis for treated and 5.3% for untreated. The treatment increased the shelf-life of the product from 3 to 12 months at ambient temperature when packaged in paper-foil-polythene laminate.     

高CO_2对冷藏富士苹果货架期品质的影响

以PE膜包装冷藏2个月的富士苹果为试材,研究4.4℃、20℃条件下果实10%CO2处理的胁迫生理变化,利用人体消化吸收模型来模拟机体的胃肠生理环境,对主要抗氧化成分多酚在人体消化吸收过程中的生物有效性进行初步评价。研究结果表明,20℃+10%CO2处理富士苹果14d,优于4.4℃+空气的保鲜效果,果实硬度大、SSC和TA含量高,失重率低,多酚类物质的总抗氧化能力较高。不同货架温度下,MDA含量均显著升高,苹果多酚可抑制丙二醛的生成,两者呈负相关。经体外消化后,多酚的生物利用度达到20%～25%,生物有效性较稳定。解剖分析、品尝对比后认为,货架期无明显CO2伤害。相同高CO2气调条件下,随着货架温度的升高,富士苹果对CO2伤害越不敏感。     

预冷结合气调对荷兰豆冷藏期间品质的影响

研究了预冷结合气调（CA）对荷兰豆冷藏期间品质的影响。采收的荷兰豆分别在常温下放置0（立即预冷）、6、12 h（对照）后置冷库内以强制通风（1.0±0.5）℃方式预冷至中心温度下降到2℃,于（1±0.5）℃、3%O₂+5%CO₂+92%N2环境下贮藏30 d。贮藏期间每10 d测定荷兰豆的色泽（a*值）,超氧阴离子（O₂^-·）产生速率,呼吸速率,丙二醛（MDA）、叶绿素、纤维素、还原糖含量,纤维素酶（CEL）、超氧化物歧化酶（SOD）和过氧化物酶（POD）活性。结果显示,预冷结合气调贮藏显著抑制了荷兰豆a*值、纤维素含量的上升和叶绿素含量的下降;还原糖含量略高于对照;维持了相对低的呼吸速率、O₂^-·产生速率和MDA含量;CEL、SOD和POD活性显著高于对照（p<0.05）,且立即预冷组优于6 h后预冷组和对照组。以上结果表明,立即预冷结合气调贮藏能有效维持荷兰豆的鲜绿色,延缓纤维化,抑制呼吸作用,提高抗氧化酶类活性,最终维持荷兰豆较好的品质。      

Effect of domestic cooking on the red cabbage hydrophilic antioxidants

The contents of vitamin C, total phenolics, anthocyanins, hydroxybenzoic and hydroxycinnamic acids as well as 2,2′‐azinobis‐(3‐ethylbenzothiazoline‐6‐sulfonic acid) monocation radical scavenging activity were evaluated in two varieties of red cabbage before and after conventional and steam‐cooking. During the conventional cooking 32.7–64.5% of vitamin C and 45.7–66.9% of total phenolics were retained in cooked tissue. Decreasing cooking water volume by half led to better retention of both phenolics (by 2.7–14.5%) and vitamin C (by 14.2–18.4%). However, shortening the cooking time by half affected the retention of phenolics and vitamin C only by 3.8–6.7% and 0–2.2%, respectively. Steam‐cooking is recommended to prevent the major loss of scavenging activity, because under these conditions, the corresponding TEAC (Trolox Equivalent Antioxidant Capacity) values were reduced only by 5–20%. Moreover, the content of vitamin C was decreased by 2.1–22.7% while losses of total phenolics were up to 10%. The phenolics are the major source of free radical scavenging activity of red cabbage, since the contribution of vitamin C to TEAC for fresh and cooked red cabbage was from 18.2 to 28.5%.     

Effect of in‐package gaseous ozone treatment on shelf life of blanched potato strips during refrigerated storage

The effect of in‐package gaseous ozone treatment on microbiological and colour quality of blanched potato strips was investigated. Potato strips were first blanched in 0.5% CaCl₂ solution at 60 °C for 10 min, second blanched in boiling water for 5 min, then exposed to room air for 30 min and packaged. Ozone gas (5%, wt/wt) was injected into each bag. Strips were subjected to a batch ozone treatment for 20 s or a continuous ozone treatment for 5, 15 or 30 min. Microbial growth was observed on day one for bags with no ozone treatment. Continuous ozone treatment was effective in extending the shelf life of potato strips compared to batch ozone treatment, and there was no microbial growth for 30‐ and 15‐min continuous ozone‐treated strips after 28 and 21 days of refrigerated storage, respectively. No significant difference was observed between the colour of blanched strips and ozone‐treated blanched strips. These results indicate that in‐package gaseous ozone treatment can be used for maintaining quality and improving shelf life of blanched potato strips.     

白藜芦醇和壳聚糖复合生物保鲜剂对冷藏鱿鱼品质的影响

为了降低鱿鱼中甲醛含量和改善鱿鱼的贮藏品质,研究了白藜芦醇和壳聚糖对鱿鱼品质和货架期的影响。实验分为对照组、白藜芦醇组(0.2%)、壳聚糖组(1.0%)、白藜芦醇(0.2%+壳聚糖1.0%)组。鱿鱼在(0±0.5) ℃贮藏20 d。以挥发性盐基氮(TVB-N)、硫代巴比妥酸值(TBA)、硬度、弹性、甲醛含量的变化、菌落总数(TVC)和感官评分作为评价指标,研究其对鱿鱼的保鲜效果。结果表明:相对对照组,白藜芦醇+壳聚糖显著(p<0.05)降低菌落总数、TVB-N、TBA值和甲醛含量,使硬度和弹性下降程度变缓,显著提高感官评分。白藜芦醇+壳聚糖能够改善鱿鱼的品质,抑制微生物的增殖,并减缓脂肪氧化,延长鱿鱼的货架期,可以用于鱿鱼的保鲜。     

低剂量辐照对鲜食核桃不同冷藏期后货架品质的影响

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Effect of decontamination on the microbial load,the sensory quality and the nutrient retention of ready-to-eat white cabbage

The effect of different decontamination treatments such as washing with sodium hypochlorite (20 and 200 mg/L), peroxyacetic acid (80 and 250 mg/L), neutral electrolysed oxidising water (4.9 and 31.7 mg/L free chlorine) and contact with 1.55 mg/L chlorine dioxide gas on the microbial and sensory quality, and the nutrient content of fresh-cut white cabbage was studied. Only rinsing with 200 mg/L sodium hypochlorite, peroxyacetic acid or contact with gaseous chlorine dioxide resulted in significantly higher reductions of the total plate count (1.5–2.5 log cfu/g) than the ones achieved by washing with tap water (0.5 log cfu/g). However, those treatments giving the best results from a microbial point of view induced significant changes in the sensory quality. Regarding the effects on nutrient content, the mechanical effects caused by water washing already reduced the vitamin C content by 16–29%. Contrary to washing with neutral electrolysed oxidising water and contact with chlorine dioxide gas, a supplementary decrease of the vitamin C content ranging between 9 and 28% was observed, when peroxyacetic acid or 200 mg/L sodium hypochlorite were used. After the use of peroxyacetic acid or gaseous chlorine dioxide, the phenol content also showed a decreasing trend, although not statistically significant. Apart from the effect of washing with water, the lipophilic nutrients were well retained after a decontamination step except for the α-tocopherol content, when peroxyacetic acid was used (−43 to 56%), and for the all-trans-β-carotene content (−8%) of cabbage in contact with gaseous chlorine dioxide. Because of its potential to reduce the initial microbial load without negative effects on the sensory quality, in combination with its limited effects on nutrient content, a treatment with 80 mg/L peroxyacetic acid is preferable to decontaminate fresh-cut white cabbage.