Induced changes in bioactive compounds of kailan-hybrid broccoli after innovative processing and storage

The glucosinolates, sulforaphane, vitamin C and lutein content after several industrial cooking methods on the new kailan-hybrid broccoli and their changes during storage for 45 days at 4 °C were studied. Boiling and sous vide induced the highest glucosinolate loss (80%), while low pressure (LP) steaming, microwaving (MW) and sous vide-MW showed the lowest (40%) loss. Glucoraphanin was the most thermostable glucosinolate. Throughout their commercial life, microwaved and grilled samples showed a decrease in total glucosinolates. Generally, myrosinase activity was completely inhibited after cooking with undetected sulforaphane contents. The initial total vitamin C dropped by up to 58% after cooking and progressively decreased during storage, with sous vide-MW (92%) and microwaving (21%) showing the highest and lowest decrements, respectively. LP steaming and microwaving were the best industrial cooking methods for maintaining the glucosinolate and vitamin C contents, and enhancing up to 7.5-fold the initial lutein content.     

Influence of Different Cooking Methods on the Concentration of Glucosinolates and Vitamin C in Broccoli

Broccoli belongs to the Brassicaceae family and the Brassica genus, also designated crucifers, which has been linked to reduced risk of certain diseases for their content of compounds like glucosinolates (GLS) and vitamin C. Isothiocyanates, nitriles, and thiocyanates are degradation products of glucosinolates, are substances that protect cells against oxidative stress, and present many other health benefits. Vitamin C also contains antioxidant properties that contribute to the beneficial effects that broccoli have for health. The present paper is an overview of the reduction of secondary plant products, such as GLS and vitamin C, by cooking. Nonetheless, these concentrations can be modified if the cell structure of the plant is disrupted, e.g., while cutting, chewing, or cooking. Myrosinase can come into contact with GLS and hydrolyze it to isothiocyanate sulforaphane or sulforaphane nitrile, depending on the environmental conditions, which produces changes in the composition and concentration of GLS. Thus, cooking induces many chemical and physical modifications in food, among which GLS and vitamin C content in broccoli can change. Vitamin C and GLS are water-soluble, which makes them more susceptible to loss during the cooking process. Despite some controversy, most reviewed studies show that conventional cooking methods (boiling, steaming, and frying) and nonconventional ones (microwaving) significantly lead to the degradation of vitamin C and GLS. Nonetheless, steaming is the conventional method that obtains the best result to better preserve these two compounds.     

Effects of stir-fry cooking with different edible oils on the phytochemical composition of broccoli

ABSTRACT:  Numerous epidemiological studies indicate that Brassica vegetables in general and broccoli in particular protect humans against cancer; they are rich sources of glucosinolates and posses a high content on flavonoids, vitamins, and mineral nutrients. The contents of total intact glucosinolates, total phenolics, vitamin C, and minerals (potassium, sodium, calcium, magnesium, iron, manganese, zinc, and copper) in the edible portions of freshly harvested broccoli (florets), which was subjected to stir-frying treatments, were evaluated. In the present work, the stir-fry cooking experiments were carried out using different edible oils from plant origin (refined olive oil, extra virgin olive oil, sunflower oil, peanut oil, soyabean oil, and safflower oil) known and used worldwide. Results showed that during stir-frying, phenolics and vitamin C were more affected than glucosinolates and minerals. Stir-fry cooking with extra virgin olive, soybean, peanut, or safflower oil did not reduce the total glucosinolate content of the cooked broccoli compared with that of the uncooked sample. The vitamin C content of broccoli stir-fried with extra virgin olive or sunflower oil was similar to that of the uncooked sample, but greater than those samples stir-fried with other oils.     

不同解冻方式对速冻西兰花品质影响

研究了微波、汽蒸、自然和静水解冻对冷冻西兰花中叶绿素、类胡萝卜素、抗坏血酸、总酚、硫苷、异硫氰酸脂、黑芥子酶和抗氧化能力的影响。结果表明,西兰花经冷冻处理后总酚、抗坏血酸、硫苷和类胡萝卜含量均有不同程度下降,异硫氰酸酯含量却显著增加了51.1%。四种解冻方式均不同程度地影响西兰花质量。微波和汽蒸解冻较自然解冻分别缩短了97.4%和94.2%的时间。其中西兰花总酚、硫苷和类胡萝卜素含量在微波解冻和汽蒸解冻之间无显著差异,但汽蒸解冻较微波解冻的抗坏血酸含量降低23.7%。静水解冻和自然解冻导致西兰花活性成分流失,而且静水解冻流失更严重。微波解冻有效地保持了西兰花中总酚、硫苷、抗坏血酸和类胡萝卜素含量,分别是自然解冻的1.15、1.20、1.93和1.39倍,从而保持了较高的抗氧化能力。此外,微波解冻和汽蒸解冻后黑芥子酶活力降低,异硫氰酸酯含量低于自然解冻和静水解冻。综合比较,微波解冻是一种较适合冷冻西兰花解冻的方式,能够较好地保留西兰花品质。     

Cooking method significantly effects glucosinolate content and sulforaphane production in broccoli florets

It is known that glucosinolate levels in Brassica vegetables can be affected during cooking but little is documented about the effect of cooking on isothiocyanate production. In this study, three cooking methods were evaluated for their effects on the contents in broccoli florets of the glucosinolates, glucoraphanin (GR), glucobrassicin (GB), neoglucobrassicin and progoitrin, as well as on sulforaphane (SF) and sulforaphane nitrile (SFN) production in broccoli florets. Two broccoli cultivars, ‘Marathon’ and ‘Booster™’, were analysed raw and after they were steamed, microwaved (with water) or boiled for 2 or 5 min. Residual cooking water from all treatments was collected and analysed for GR and GB to determine the extent of leaching of intact glucosinolates. Irrespective of time, steaming resulted in significantly greater retention of GR, GB and SF, while boiling and microwave cooking resulted in significant losses of GR, GB and SF in both varieties. Glucosinolate content in the residual cooking water was highest after boiling and microwaving. Loss of SF production was primarily due to both leaching of GR into cooking water and thermal inhibition of ESP and myrosinase once internal floret temperatures exceeded 70 °C. Cooking method can significantly alter content of potentially beneficial compounds in broccoli florets and optimal SF ingestion may be obtained by eating raw or lightly steamed broccoli florets.     

The antioxidant capacity and polyphenol content of organic and conventional retail vegetables after domestic cooking

Vegetable consumption is associated with health benefits. Organic foods are thought to have higher contents of antioxidant substances. The objective of this work is to quantify soluble and hydrolyzable polyphenols, ascorbic acid, and the antioxidant capacity of fresh conventional and organic retail vegetables (potato, carrot, onion, broccoli, and white cabbage) while evaluating the effect of boiling, microwaving, and steaming on these parameters. The recovery rate for soluble and hydrolyzable polyphenols was variable according to the vegetable analyzed. However, soluble polyphenols resulted in lower recovery rates than did hydrolyzable phenolics after cooking. Organic vegetables showed higher sensitivity to heat processing than did conventionally grown vegetables. In general, cooking was found to lead to reductions in the antioxidant capacity for most vegetables, with small differences between the cooking methods applied. Even with the alterations in their content, polyphenols showed a positive correlation with antioxidant capacity in raw and cooked vegetables from both types of agriculture.     

NaCl胁迫对西兰花芽苗叶黄素积累及抗氧化能力的影响

为探究NaCl胁迫对西兰花芽苗叶黄素富集及抗氧化能力的影响,本实验以“青峰”西兰花种子为实验原材料,研究了不同浓度NaCl溶液处理对西兰花芽苗的芽长、鲜重、干重、含水率、可溶性蛋白、还原糖、丙二醛、脯氨酸、叶黄素含量及抗氧化酶[超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）]活性的影响。结果表明,不同NaCl浓度对西兰花芽苗生长影响较大,随NaCl浓度由0~300 mmol/L变化,叶黄素含量先升高后下降。经100 mmol/L NaCl胁迫处理至第4 d收获的芽苗中叶黄素含量为546.25 μg/g,比对照组增加了37.54%,该条件下芽苗的芽长、鲜重、干重、含水率、可溶性蛋白、还原糖含量也均明显提高,较对照组分别增加了20.88%、161.16%、68.65%、2.86%、54.90%和40.0%,SOD、POD、CAT抗氧化酶活性与对照组相比分别增加了36.26%、14.62%、32.34%。本研究为通过NaCl胁迫西兰花种子萌发来提高叶黄素含量提供了新的方式,为开发功能性西兰花芽苗食品提供参考。     

Influence of blanching and freezing broccoli (<Emphasis Type="Italic">Brassica oleracea</Emphasis> var. <Emphasis Type="Italic">italica</Emphasis>) prior to storage and cooking on glucosinolate concentrations and myrosinase activity

Glucosinolates contribute to the chemoprotective effects of Brassica vegetables. The influence of blanching and freezing broccoli, followed by storage or cooking, on its glucosinolate concentration and myrosinase activity was investigated. Myrosinase activity was reduced by 93%, while glucosinolate concentration was unaltered after blanch-freezing broccoli. Blanch-frozen Brassica retained the glucosinolate content of its fresh counterpart after storage at T = −20 °C for up to 90 days. Fresh or blanch-frozen broccoli was stir-fried, boiled, boiled and kept hot for 2 h, or left uncooked. Stir-frying retained the highest glucosinolate concentration and myrosinase activity, regardless of pre-cooking. Boiling and keeping blanch-frozen broccoli hot completely denatured myrosinase and decreased glucosinolate concentration by 42%. Aromatic and indole glucosinolates were reduced to a larger extent than aliphatic glucosinolates, especially when boiled broccoli was kept hot. The final concentration of glucosinolates in Brassica is influenced by cooking, while the myrosinase activity is modified by pre-treatment and subsequent cooking.     

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。     

Optimization of a process to obtain selenium-enriched freeze-dried broccoli with high antioxidant properties

Broccoli exhibits a high content of antioxidant and anticarcinogenic compounds, such as polyphenols and selenium. Since it is mostly consumed as a processed food, elucidating the processing conditions that minimize nutritional losses becomes relevant. The process composed of a blanching step followed by freeze-drying of selenium-enriched broccoli was optimized, in order to maximize the content of Se-methyl selenocysteine (SMSeC), total polyphenols content and anti-radical power (ARP). The optimal blanching conditions agreed for the three responses, and were immersion in water at 72 °C during 1 min. The optimal freeze-drying conditions were slow freezing rate, atmospheric pressure (96.13 kPa), and application of infrared radiation (IR). These conditions allowed keeping 25% ARP, 18% polyphenols content and 174% SMSeC compared to the fresh vegetable. These results will help in establishing the most adequate processing conditions that allow keeping the functional properties of broccoli as a processed food.     

The effects of cooking method on selected quality traits of broccoli and green asparagus

Broccoli and green asparagus were cooked using boiling water, steam, microwave oven and combi oven with overheated steam and combination of hot air with overheated steam (only broccoli). Vegetables were analysed for chlorophylls a and b, carotenoids, total polyphenols, antioxidant activity, colour parameters and sensory properties. Cooking in the combi oven with overheated steam was an effective method to achieve the highest levels of polyphenols and antioxidant activity, but it negatively influenced the contents of chlorophylls in both vegetables and carotenoids in asparagus. Boiling and cooking in the combi oven with overheated steam or hot air and steam ensured the best and comparable sensory properties of broccoli. Asparagus showed a lower susceptibility to heat treatments than broccoli as none of the treatments applied caused significant differences in colour redness and yellowness, polyphenol content and sensory properties of this vegetable.     

等离子体处理对西兰花芽苗生产及活性物质含量的影响

为实现西兰花芽苗中萝卜硫素、多酚、黄酮等生物活性物质的富集,以此来降低生产成本,本研究采用等离子体处理诱导方法,研究等离子体处理条件对不同品种西兰花芽苗生长和活性物质的影响。结果显示:等离子体处理电压、时间对西兰花芽苗发芽状态及活性物质含量都有显著影响（P<0.05）,在电压30 kV,处理时间2 min条件下,西兰花芽苗发芽5 d后发芽率、芽长、芽重较对照都有显著增加,萝卜硫素含量达到3.24 mg/g DW,较未处理提高了6.75倍。不同品种西兰花芽苗中萝卜硫素、总酚、总黄酮含量及抗氧化活性存在显著差异（P<0.05）,其中马尼拉的萝卜硫素和总硫苷含量最高,而曼陀绿和绿玉的总酚和总黄酮含量最高。等离子体处理后文兴、马尼拉、绿玉和绿剑的总酚和总黄酮含量及抗氧化能力较对照处理均有所提高。综上,西兰花芽苗经等离子体处理是富集萝卜硫素的有效方式,可显著提升芽苗功效并降低萝卜硫素获取成本。     

The influence of processing and preservation on the retention of health-promoting compounds in broccoli

ABSTRACT:  In this work the effects of common household practices such as chilling, freezing, and cooking on vitamin C retention in broccoli (Marathon cv.), as well as their influence on the release of sulforaphane upon enzymatic hydrolysis of glucoraphanin by the endogenous enzyme myrosinase, were investigated. When chilled at 6 °C and 95% R.H. for 35 d, broccoli showed a vitamin C and sulforaphane loss of about 39% and 29%, respectively, while storage at –18 °C for 60 d resulted in similar losses, but mainly due to the blanching step. Boiling, steaming, microwaving, pressure-cooking, and the combined use of pressure and microwaves were the cooking methods investigated. Boiling and steaming caused significant vitamin C losses, 34% and 22%, respectively, while with the other treatments more than 90% retention was observed. Sulforaphane was no more detectable after boiling or steaming, while pressure/microwave cooking did not cause any significant loss. The quantitative distribution of these moieties in the florets and stems of fresh and chilled broccoli was also investigated.     

Steam processed broccoli (Brassica oleracea) has higher antioxidant activity in chemical and cellular assay systems

Thermally processed fruits and vegetables have long been considered to have a lower nutritional value compared with the fresh produce. This consideration is based on the fact that vitamin C or other thermolabile compounds may lose their activity due to oxidation or in consequences of leaching into the water during home cooking or industrial processing, such as blanching. In this study, broccoli, one of the major agricultural products was exposed to steam; and total antioxidant activity was measured by oxygen radical capacity (ORAC) analysis and a cellular measure of reactive oxygen species (ROS) assay. The study also evaluated the level of total phenolics and total flavonoid content in fresh and steam processed broccoli samples. The result clearly showed that steam-processing elevated the total ORAC (hydrophilic, lipophilic) value by 2.3 fold. Measuring cellular levels of ROS, we found that the hydrophilic part of a steam processed broccoli had a significant reduction of 2,2′-azobis [2-amidinopropane] dihydrochloride (AAPH) induced intracellular ROS level in comparison to that of fresh counterpart. Total phenolic content and total flavonoid content also increased in steamed-processed broccoli. Chromatographic analysis showed that a non-phenolic fraction which appeared unbound on a cosmosil 140 C18 resin contributed 54%, and the phenolic pool eluted by 50–80% methanol contributed 41% of its total increase in ORAC value. Steam processed broccoli gave significant cytoprotection in PC-12 cell line and this neuroprotective efficacy warrant further investigation. This information may have a significant impact on consumers’ food selection, depending on the processing technology used to process agricultural products.     

Impact of cooking methods on folates,ascorbic acid and lutein in green beans (Phaseolus vulgaris) and spinach (Spinacea oleracea)

Folates, ascorbic acid (vitamin C) and lutein (antioxidant carotenoid) concentrations were determined after cooking (boiling and steaming) fresh, frozen and canned green beans (Phaseolus vulgaris) and spinach (Spinacea oleracea). The aim of this study was to qualify and quantify the loss of water soluble (folates and ascorbic acid) and lipid soluble (lutein) micronutrients in the cooked products and liquids and the canning liquor. In canned products, folates were found in the canning liquor. Boiling regardless of product reduced plant tissue folates and ascorbic acid but not lutein concentrations. Loss of folates during boiling occurred due to leaching (diffusion) and ascorbic acid due to temperature (heating). Steaming reduced ascorbic acid but not folate or lutein concentrations.     

Improving the phytochemical composition of broccoli sprouts by elicitation

In order to increase the concentrations of bioactive compounds in broccoli sprouts, exogenous elicitors: methionine, tryptophan, chitosan, salicylic acid (SA) and methyl jasmonate (MeJA) were sprayed at different concentrations during germination. The effects of the elicitors on vitamin C, phenolic compounds and glucosinolate levels were assessed in 3, 5 and 7-days old seedlings. The application of 200, 300 μM SA and 0.01% chitosan induced increases, by 26%, 18% and 54%, respectively in the content of vitamin C in 5 days old broccoli sprouts. Flavonoid concentration was also increased by 31% and 33% after 10 μM MeJA and 100 μM SA treatments, respectively in 7 days old broccoli sprouts. In contrast, methionine or tryptophan solutions did not positively affect the vitamin C or the phenolic compounds in the sprouts. The individual classes of glucosinolates respond differently to the elicitor treatment. Methionine, a sulphur-containing amino acid, applied at 5 mM, significantly increased, by 32%, the levels of aliphatic glucosinolates. However, indole glucosinolates presented a significant response to the induction with tryptophan, SA or MeJA treatments. Tryptophan at 10 mM concentration augmented by 1.8-fold the indole glucosinolate concentration in 7 days old broccoli sprouts, and the treatments of 100 μM SA and 25 μM MeJA also induced significantly higher amounts of indole glucosinolates (by 33% and 51%, respectively) in 7 days old treated broccoli sprouts. Therefore, the application of elicitors could be a useful tool for improving the bioactive metabolites in broccoli sprouts for fresh consumption or functional ingredients for nutraceuticals foods.     

Development of a Novel Functional Soup Rich in Bioactive Sulforaphane Using Broccoli (Brassica oleracea L. ssp. italica) Florets and Byproducts

Broccoli florets are rich in health-promoting compounds such as glucoraphanin, the precursor of the bioactive compound sulforaphane. In addition, broccoli byproducts such as stalk also contain health-promoting compounds and represent attractive ingredients in the development of functional foods. The bioconversion of glucosinolates into bioactive isothiocyanates is affected by many factors including heat and therefore cooking of Brassica such as broccoli may result in significant loss of sulforaphane production. The aim of this study was to develop a suitable food system as a vehicle for the delivery of sulforaphane in the human diet in adequate quantities. To this end, the feasibility of dry-mix ready soup as a food matrix for the delivery of broccoli floret and byproducts was evaluated. In particular, this study investigated the bioconversion of glucosinolates into bioactive isothiocyanates during the cooking process of this novel food product by microwave heating. In addition to total isothiocyanate and sulforaphane content, other key physical and biochemical quality attributes of the broccoli floret- and byproduct-enriched soups were investigated. Total isothiocyanate and sulforaphane content in floret- and stalk-enriched soups was high in both cases and increased in the order stalk<floret. The overall acceptability of stalk containing soups was not significantly different compared with the control soups, whereas floret containing soups received significantly lower acceptability scores. These results suggest that ready soups prepared by microwave heating represent a feasible food product for the delivery of broccoli florets and byproducts which is compatible with the bioconversion of glucosinolates into bioactive isothiocyanates.     

发酵对西兰花硫代葡萄糖苷缓解秀丽隐杆线虫氧化损伤的影响

为探讨乳酸菌发酵对西兰花硫代葡萄糖苷（简称硫苷）抗氧化能力的影响，本研究以植物乳杆菌发酵西兰花，测定硫苷的代谢产物组分和体外抗氧化能力。同时，考察发酵硫苷对秀丽隐杆线虫抗应激能力和抗氧化指标的影响。结果表明，乳酸菌发酵增强了西兰花硫苷体外抗氧化能力。线虫实验显示发酵硫苷能够提高秀丽隐杆线虫在热应激和氧化应激下的存活率，显著降低线虫体内活性氧和脂褐素水平（P<0.05），提高超氧化物歧化酶活力，从而缓解线虫氧化损伤。通过乳酸菌发酵可以提高西兰花硫苷的抗氧化活性，为西兰花等十字花科蔬菜中硫苷的开发利用提供理论支撑。     

Cooking methods of Brassica rapa affect the preservation of glucosinolates,phenolics and vitamin C

Cooking Brassica vegetables as a domestic processing method has a great impact on health-promoting bioactive compounds: glucosinolates (GLS), flavonoids, hydroxycinnamic acids, and vitamin C. In Galicia (NorthWestern Spain), one of the most consumed horticultural crops is Brassica rapa, by using the leaves (turnip greens) and the young sprouting shoots (turnip tops) in different culinary preparations. In order to determine the effect of cooking, on turnip greens and turnip tops, bioactive GLS, flavonoids, hydroxycinnamic acids and vitamin C were analysed and simultaneously determined. The level of retention of each individual compound after cooking procedures was evaluated in the edible organs, and also in the cooking water, in order to compare their composition to a fresh uncooked control. Steaming, conventional boiling, and high-pressure cooking, traditional processing methods of this kind of vegetables, were the three domestic processing methods used in this work. Results showed that total GLS and phenolics were significantly affected by the cooking procedure and the loss rate varied among individual compounds. Steaming was the method that better preserved GLS and phenolic compounds. Conventional boiling and high-pressure cooking methods presented similar rate of losses of total GLS content (64%) and total phenolic content (more than 70%). Degradation among glucosinolate classes, aliphatic or indolic, was similar. The total flavonoids lost in turnip greens were 64% and 67% for conventional boiling and high-pressure, respectively. The main losses were caused by leaching into the cooking water. The concentration of vitamin C suffered a drastic loss in the process of sample handling and after cooking. Despite the fact that any cooking procedure affected negatively the nutritional composition of the turnip greens and tops, our results showed high retentions of individual compounds in steaming, and the lowest retentions were obtained in the traditional high-pressure cooking. High retention of health-promoting compounds in the cooking water should be considered for increasing the intake of properties of B. rapa.     

不同烹调方式对蔬菜植物化学物及V_C的影响

目的:研究不同家庭烹调方法对紫薯、西兰花和青辣椒中的花色苷、硫苷、辣椒素和V C的影响。方法:三种蔬菜经过微波、蒸制、焯制和油炒等烹调后,以pH示差法测定花色苷,以高效液相色谱法测定硫苷和辣椒素,以2,6-二氯靛酚滴定法测定V C。结果:保存V C效果:蒸制>微波蒸制,焯制>油炒>微波煮制;保存花色苷效果:蒸制>微波蒸制,且蒸制使花色苷增加;保存总硫苷效果:油炒>焯制>微波煮制;保存辣椒素效果:微波煮制>焯制>油炒。结论:若控制烹调时间不过长,蒸制是最适宜保存蔬菜植物化学物及维生素的烹调方法。