Effect of visible light treatments on postharvest senescence of broccoli (Brassica oleracea L.)

BACKGROUND: Broccoli (Brassica oleracea L.) is a rapidly perishable vegetable crop. Several postharvest treatments have been applied in order to delay de‐greening. Since light has been shown to have an effect on pigment accumulation during development and darkness is known to induce senescence, the effect of continuous and periodic exposure to low‐intensity white light at 22 °C on postharvest senescence of broccoli heads was assayed. RESULTS: Exposure to a constant dose of 12 µmol m^?2 s^?1 was selected as the most suitable treatment and was employed for subsequent experiments. During the course of the treatments, hue and L* values as well as chlorophyll content and visual observation of florets indicated an evident delay in yellowing in treated samples compared with controls. No statistically significant differences in total protein content were found, but soluble protein content was higher in treated samples. Total and reducing sugar as well as starch levels decreased during postharvest senescence, with lower values in control samples. CONCLUSION: The results of this study indicate that storage under continuous low‐intensity light is an efficient and low‐cost treatment that delays postharvest senescence while maintaining the quality of harvested broccoli florets. Copyright © 2010 Society of Chemical Industry     

Effect of drying kinetics on main bioactive compounds and antioxidant activity of acerola (Malpighia emarginata D.C.) residue

This study investigates the drying kinetics of residue of acerola, in a fixed‐bed dryer, analysing the effect of the process variables on the antioxidant properties of the residue. A complete factorial design 3² has been performed, where the independent variables studied were as follows: air velocity (0.5, 1.0 and 1.5 m s^?1) and air‐drying temperature (40, 50 and 60 °C). The bioactive compounds studied were L‐ascorbic acid, total phenolic, total flavonoids and antioxidant activity (expressed as IC₅₀) was determined using free radical DPPH^?. Both independent variables studied have shown to be statistically significant. The content of ascorbic acid was the highest at 60 °C and 1.0 m s^?1 (126.2 ± 0.004 mg 100 g^?1) while for the fresh residue 16.12 ± 0.003 mg 100 g^?1, whereas the total phenolic showed the highest content at 50 °C and 1.5 m s^?1 (46.2 ± 0.003 mg gallic acid.100 g^?1) while for the fresh residue 12.59 ± 0.001 mg gallic acid.100 g^?1. The drying conditions play an important role in determining the final quality of the product mainly in terms of antioxidant activity.     

鲜切西兰花在贮藏过程中自身抗氧化活性的变化

目的研究鲜切西兰花在4℃条件下贮藏14 d内自身抗氧化活性的变化。方法采用DPPH体系、Fenton体系和还原体系研究鲜切西兰花在贮藏期间抗氧化能力的变化。同时还测定了与西兰花抗氧化能力有关的营养成分与酶活性的变化,包括总酚和VC、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)和超氧化物歧化酶(SOD)。结果鲜切西兰花在贮藏期间总抗氧化能力在贮藏前12 d呈逐渐上升状态,之后缓慢降低;清除羟自由基的能力很高,但在贮藏期内呈先缓慢降低后回升的趋势;还原能力在贮藏前10 d呈上升趋势,之后大幅度降低。总酚和APX活性均呈先上升后下降的趋势;VC含量从80 mg/100 g降低到60 mg/100 g,之后变化不大;CAT活性和SOD活性在贮藏前期呈现降低趋势,中期回升,后期又逐渐降低。结论鲜切西兰花的抗氧化能力在8~12 d期间较高。     

Effect of drying conditions on the retention of phenolic compounds,anthocyanins and antioxidant activity of roselle (Hibiscus sabdariffa L.) added to yogurt

To evaluate the use of lixiviate roselle calyxes as an alternative source of bioactive compounds, they were subjected to dehydration in a vibrofluidised bed dryer after which some chemical parameters such as the retention of monomeric anthocyanins (MA), phenolic compounds, polymeric colour and antioxidant activity were determined. Drying curves showed both a constant drying period and a decreasing falling rate period. The different drying conditions showed significant differences in the chemical parameters. Using the dry residue with the best bioactive compounds content, it was possible to develop a dairy beverage (yogurt). The results confirmed that lixiviated roselle calyxes could be a competitive alternative for traditional products, such as grapes or bilberries, in terms on their antioxidant activity and stability when it is added as a source of bioactive compounds.     

Effect of storage on the bioactive compounds and antioxidant activity of quince nectar

The changes of bioactive components and antioxidant activity of quince nectar were determined during 9 months of storage at 5, 20, 30 and 40 °C. The amount of total phenolics, flavonoids and antioxidant activity was significantly declined during storage at all temperatures. Loss of L‐ascorbic acid at 5, 20, 30 and 40 °C was 32.08%, 43.69%, 65.21% and 88.82%, respectively. L‐ascorbic acid degradation was in accordance with the first‐order reaction kinetics, and activation energy was found as 43.65 kJ mol^?1. After 9 months of storage, Hydroxymethylfurfural (HMF) contents of quince nectars were 15.01, 16.64, 21.69 and 57.89 mg kg^?1 at 5, 20, 30 and 40 °C, respectively. HMF accumulation fitted a zero‐order kinetic model, and activation energy was found as 88.30 kJ mol^?1. A significant correlation was found among L‐ascorbic acid, total phenolics, flavonoids and antioxidant activity.     

西兰花乳清发酵饮料工艺优化及其抗氧化活性研究

目的 优化西兰花乳清发酵饮料工艺并研究其抗氧化活性.方法 以乳清、西兰花为原料, 采用益生菌菌蔬酵素浸泡发酵, 通过单因素和正交实验筛选最优工艺, 进一步添加品质改良剂调配, 制备西兰花乳清发酵饮料, 并对产品的感官、理化、微生物以及抗氧化活性进行研究.结果 筛选的最佳工艺为: 切块西兰花添加量20%, 白砂糖15%,...     

Influence of cut type on quality,antioxidant substances and antioxidant activity of fresh-cut broccoli

In order to clarify an efficient and convenient method to increase the antioxidant activity in broccoli, this study intended primarily to elucidate the effect of cutting type on the quality parameters, antioxidant substance contents and antioxidant activity of broccoli using different floret diameters of 10 × 10 cm (CS1), 5 × 5 cm (CS2), 2.5 × 2.5 cm (CS3) and shredded florets (CS4). The results showed that chlorophyll, total soluble solid, vitamin C and reduced glutathione contents of fresh-cut broccoli were decreased obviously during the storage. However, there was a significant influence of cutting type on the enzymatic activities involved in phenolic synthesis and oxidation including phenylalanine ammonia-lyase, cinnamate 4-hydroxylase, and polyphenol oxidase, which contributed to increasing phenolic content by 26.8%, 30.9%, 46.0%, and 51.3% in CS1, CS2, CS3 and CS4, respectively, and further enhanced the antioxidant activity by more than 60% in fresh-cut broccoli. Moreover, the activities of antioxidant-related enzymes, including superoxide dismutase, peroxidase and catalase, were increased significantly in fresh-cut broccoli. In conclusion, the cutting types had no significant effect on quality but clearly influenced the antioxidant substances and activities of broccoli; therefore, this study provided an efficient and convenient method to enhance the potential nutritional value of broccoli.     

Thermal Stability of l-Ascorbic Acid and Ascorbic Acid Oxidase in Broccoli (Brassica oleracea var. italica)

ABSTRACT: The thermal stability of vitamin C (including l -ascorbic acid [l -AA] and dehydroascorbic acid [DHAA]) in crushed broccoli was evaluated in the temperature range of 30 to 90 °C whereas that of ascorbic acid oxidase (AAO) was evaluated in the temperature range of 20 to 95 °C. Thermal treatments (for 15 min) of crushed broccoli at 30 to 60 °C resulted in conversion of l -AA to DHAA whereas treatments at 70 to 90 °C retained vitamin C as l -AA. These observations indicated that enzymes (for example, AAO) could play a major role in the initial phase (that is, oxidation of l -AA to DHAA) of vitamin C degradation in broccoli. Consequently, a study to evaluate the temperature–time conditions that could result in AAO inactivation in broccoli was carried out. In this study, higher AAO activity was observed in broccoli florets than stalks. During thermal treatments for 10 min, AAO in broccoli florets and stalks was stable until around 50 °C. A 10-min thermal treatment at 80 °C almost completely inactivated AAO in broccoli. AAO inactivation followed 1st order kinetics in the temperature range of 55 to 65 °C. Based on this study, a thermal treatment above 70 °C is recommended for crushed vegetable products to prevent oxidation of l -AA to DHAA, the onset of vitamin C degradation. Practical Application : The results reported in this study are applicable for both domestic and industrial processing of vegetables into products such as juices, soups, and purees. In this report, we have demonstrated that processing crushed broccoli in a temperature range of 30 to 60 °C could result in the conversion of l -ascorbic acid to dehydroascorbic (DHAA), a very important reaction in regard to vitamin C degradation because DHAA could be easily converted to other compounds that do not have the biological activity of vitamin C.     

Effect of dehydration on phenolic compounds and antioxidant activity of blackcurrant (Ribes nigrum L.) pomace

This study examined the effect of dehydration on the phenolic compounds and antioxidant activity of blackcurrant (Ribes nigrum L.) pomaces (DBP) subjected to hot air oven drying (HOD), industrial rotary drying (IRD) and freeze drying (FD). Temperature and residence time were evaluated for HOD, whereas air-on and air-off temperature, ratio of drum rotor speed to air speed and particle size were evaluated for IRD. The highest total anthocyanins (ATC) and flavonols (FLV) were obtained in particle size of> 5.0 mm using IRD at 475°C/97°C (air-on/air-off) and higher ratio of drum rotor speed to air speed. Smaller size particles were found susceptible to degradation due to high temperature and retention time applied in IRD, resulting in loss of phenolic compounds in DBP, and thus, HOD was deemed more suitable. Overall, drying method selection and parameters of operation are key in preserving the concentrations of individual HCA and FLV in DBP.     

Effect of hot air treatments on senescence and quality parameters of harvested broccoli (Brassica oleracea L var Italica) heads

Treatments with hot air were applied to broccoli (Brassica oleracea L) florets to investigate the effect on several quality and senescence parameters. To select the optimum treatment, florets were treated with different combinations of time/temperature ranging from 1 to 3 h and 37 to 50 °C and then placed in darkness at 20 °C. Most treatments delayed yellowing and loss of chlorophylls, except those performed at 37 °C, which accelerated senescence. Treatment at 48 °C for 3 h caused the highest delay in chlorophyll loss and was chosen to analyse its effect on quality and senescence. Non‐treated florets showed yellowing and reduced their chlorophyll content during storage. Heat treatment delayed the onset of chlorophyll catabolism by 1 day and slowed down the rate of degradation. Treated florets also showed lower losses of total sugars and proteins and an inhibition of protein solubilisation. Control heads showed an increment in CO₂ production, which was not detected in heat‐treated florets. Total antioxidants decreased and thiobarbituric acid‐reactive substances (TBARS) increased during storage. The treatment delayed the decrease in antioxidant content and inhibited the increment in TBARS. In conclusion, treatment at 48 °C for 3 h delayed broccoli senescence at 20 °C and contributed to maintaining an overall better quality of the product. Copyright © 2005 Society of Chemical Industry     

Quality parameters and antioxidant properties in organic and conventionally grown broccoli after pre‐storage hot water treatment

BACKGROUND: Demand for broccoli has increased due to its high content of bioactive compounds. However, broccoli is a perishable commodity with a short shelf life mainly due to dehydration, yellowing and losses of bioactive compounds. Thus, efficient treatments to preserve broccoli quality are needed. RESULTS: The effect of heat treatment on senescence and antioxidant compounds evolution during storage at 20 °C was evaluated in organic and conventionally grown broccoli. Senescence evolved quickly as manifested by floral head yellowing, which was higher in conventional than in organic broccolis, but senescence was significantly delayed by heat treatment. All organic acids, including ascorbic acid, were found at higher concentrations in organic than in conventional broccoli at harvest but decreased during storage in all broccolis. Phenolic concentration and antioxidant activity (in both hydrophilic and lipophilic fractions) also decreased during storage, although these decreases were higher in conventional than in organic broccolis, and no differences were found attributable to heat treatment. CONCLUSIONS: Heat treatment was effective in delaying broccoli senescence, manifested by chlorophyll retention. In addition, organic broccoli maintained higher concentrations of bioactive compounds (ascorbic acid and phenolics) and antioxidant potential during storage than conventional broccoli, with higher potential health beneficial effects. © 2012 Society of Chemical Industry     

桑葚果酒全渣发酵过程中生物活性物质及其抗氧化活性变化的研究

以桑葚干果为实验原料,考察桑葚发酵液中总酚、类黄酮、花青素的含量及抗氧化活性能力在发酵过程中的变化情况。结果表明:发现前发酵10 d的类黄酮和花青素类物质受发酵的影响逐渐变少,而总酚类物质含量逐渐升高;抗氧化活性总体上呈先升后降的趋势,相比于发酵开始时下降了近50%。DPPH和FRAP法相较于ABTS法,更适合表征桑葚发酵液的抗氧化活性变化情况。桑葚酒再经过40 d陈酿最终残还原糖为14.21 g/kg,乙醇浓度为101.6 g/kg,总酚含量2.124 g/kg,花青素含量579.4 mg/kg,类黄酮41.2 g/kg,DPPH自由基清除率为21.1%,FRAP抗氧化活性为40.9μmol Fe²⁺/L,总浸出物为23.241 g/L,符合国家相关标准,为进一步开发高生物活性桑葚精深加工产品提供了一条可行的途径。