Influence of Cooking Methods on Antioxidant Activity of Vegetables

ABSTRACT:  The influence of home cooking methods (boiling, microwaving, pressure-cooking, griddling, frying, and baking) on the antioxidant activity of vegetables has been evaluated in 20 vegetables, using different antioxidant activity assays (lipoperoxyl and hydroxyl radicals scavenging and TEAC). Artichoke was the only vegetable that kept its very high scavenging-lipoperoxyl radical capacity in all the cooking methods. The highest losses of LOO· scavenging capacity were observed in cauliflower after boiling and microwaving, pea after boiling, and zucchini after boiling and frying. Beetroot, green bean, and garlic kept their antioxidant activity after most cooking treatments. Swiss chard and pepper lost OH· scavenging capacity in all the processes. Celery increased its antioxidant capacity in all the cooking methods, except boiling when it lost 14%. Analysis of the ABTS radical scavenging capacity of the different vegetables showed that the highest losses occurred in garlic with all the methods, except microwaving. Among the vegetables that increased their TEAC values were green bean, celery, and carrot after all cooking methods (except green bean after boiling). These 3 types of vegetables showed a low ABTS radical scavenging capacity. ccording to the method of analysis chosen, griddling, microwave cooking, and baking alternately produce the lowest losses, while pressure-cooking and boiling lead to the greatest losses; frying occupies an intermediate position. In short, water is not the cook's best friend when it comes to preparing vegetables.     

Effect of cooking on the antioxidant properties of coloured peppers

Pepper (Capsicum annum L.) has long been recognized as an excellent source of antioxidants, being rich in ascorbic acid and other phytochemicals. This study was conducted to investigate the effect of different cooking methods on the antioxidant properties of coloured peppers. Six varieties of peppers were subjected to different cooking methods, such as microwave heating, stir-frying and boiling in water, for 5 min individually. The cooked and raw peppers were analyzed for radical-scavenging activity (RSA) and total polyphenol content (TP) using 1,1-diphenyl-2-picrylhydrazyl–high-pressure liquid chromatography (DPPH)–HPLC and Folin-Ciocalteu methods, respectively. The samples were also evaluated for ascorbic acid content (AsA) by HPLC. Total carotenoid content was determined spectrophotometrically. Results suggest that there is no significant (P > 0.05) difference in RSA, TP, AsA and total carotenoid contents between the cooked and raw peppers when processed for 5 min. However, the cooked peppers show marked differences (P < 0.05) in the RSA, TP and AsA when cooked for 5 min in boiling water with further reduction observed after boiling for 30 min. This may be due to the leaching of antioxidant compounds from the pepper into the cooking water during the prolonged exposure to water and heat. Therefore, it is vital to use less water and cooking time and also to consume the water used for boiling so as to obtain the optimum benefits of bioactive compounds present in peppers. It is concluded that microwave heating and stir-frying without using water are more suitable cooking methods for pepper, to ensure the maximum retention of antioxidant molecules.     

In vitro α-glucosidase and pancreatic lipase inhibitory activities and antioxidants of Samnamul (Aruncus dioicus) during rehydration and cooking

In vitro α-glucosidase and pancreatic lipase inhibitory activities of ethanol extracts of samnamul (dried young shoots of Aruncus dioicus) during rehydration (soaking, 30 min boiling, and re-soaking in water) and subsequent cooking at 180°C with/without perilla oil were determined for evaluation of its anti-diabetic and antiobesity potential. Polyphenol and flavonoid contents were monitored by spectrophotometry. Rehydration and boiling of samnamul reduced α-glucosidase and pancreatic lipase inhibitory activities as well as polyphenol and flavonoid contents, whereas soaking time did not have a significant effect. Of the rehydration and cooking processes, 30 min boiling was the most critical in reducing anti-diabetic and anti-obesity activities as well as antioxidant contents. Perilla oil addition improved α-glucosidase inhibitory activity, possibly through polyphenol addition. These results suggest that dietary intake of samnamul can reduce the risks of diabetes and obesity, and perilla oil can additionally improve its health benefits.     

Antioxidant compound contents and antioxidant activity before and after cooking in sweet and bitter Chenopodium quinoa seeds

The antioxidant activity and the relationship between total antioxidant activity and the main classes of antioxidants in the seeds of bitter and sweet Chenopodium quinoa seeds were measured before and after boiling, in order to establish which one showed the best antioxidant property and how a traditional cooking method could affect it. Our results, obtained by using DPPH (1,1-diphenyl-2-picrilhydrazyl) and FRAP (Ferric Reducing/Antioxidant Power) methods, showed that antioxidant activity of bitter seeds was higher than that of sweet seeds. This activity principally depended on phenols and flavonoids in bitter seeds, while it was mainly due to phenol, flavonoid and carotenoid compounds in sweet seeds. Moreover, boiling caused a significant loss of antioxidant capacity in water.     

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.     

Effect of different cooking methods on the antioxidant activity of some vegetables from Pakistan

The effects of different cooking methods (boiling, frying and microwave cooking) on the antioxidant activity of some selected vegetables (peas, carrot, spinach, cabbage, cauliflower, yellow turnip and white turnip) were assessed by measuring the total phenolic contents (TPC), reducing power and percentage inhibition in linoleic acid system. TPC (gallic acid equivalents g/100 g of dry weight) and reducing power of the methanolic extracts of raw‐, microwaved‐, boiled‐ and fried vegetables ranged 0.333–2.97, 0.52–2.68, 0.48–2.08, 1.00–2.02 and 0.391–2.24, 0.822–1.10, 0.547–1.16, 0.910–4.07, respectively. The level of inhibition of peroxidation ranged 71.4–89.0, 66.4–87.3, 73.2–89.2 and 77.4–91.3%, respectively. Antioxidant activity of the vegetables examined was appreciably affected because of varying cooking treatments. TPC of vegetables, generally, decreased by boiling, frying and microwave cooking. There was a significant (P < 0.05) increase in reducing power as a result of frying. However, boiling and microwave cooking did not affect reducing power. Inhibition of peroxidation increased by boiling and frying, whereas, in contrast it was decreased by microwave cooking. The results of the present investigation showed that all the cooking methods affected the antioxidant properties of the vegetables; however, microwave treatment exhibited more deleterious effects when compared with those of other treatments. Thus an appropriate method might be sought for the processing of such vegetables to retain their antioxidant components at maximum level.     

Chemical and biochemical characterisation of an IGP ecotype chestnut subjected to different treatments

This study investigated and compared the polyphenols content, the antioxidant activity, the mineral and trace elements concentrations of raw chestnuts, chestnuts subjected to different cooking methods and cured chestnuts. The aim was to verify the quality of raw fruit and the changes induced from treatments, such as roasting, boiling and curing. The total polyphenol content and the antioxidant activity decreased in cured and heat-treated chestnuts, when compared to raw material, in the following order: cured > roasted > boiled shelled > boiled unshelled fruits. Specific phenolic compounds showed significant effects of cooking treatments, while the concentrations of minerals (Ca, K, Mg, and Na) and trace elements (As, Cd, Cu, Fe, Hg, Mn, Ni, Pb and Zn) also varied.     

烹调方式及4℃模拟配送中青椒营养品质及亚硝酸盐含量变化

本实验通过测定同一烹调成熟度下我国主要烹调方式及模拟餐饮冷藏配送过程中青椒营养品质和亚硝酸盐含量的变化,确定青椒最佳冷藏配送时间以及准确评估我国居民营养素的摄入量。以青椒为原料,以硬度作为烹调成熟度的统一标准,以传统烹调方式炒制、蒸制、煮制、微波为烹调方法,研究青椒在烹调后及模拟4℃冷藏配送0、1、4、8、12、24 h复热青椒的营养品质及亚硝酸含量变化。结果表明:烹调使VC含量显著降低,烹调后其真实保存率为76.3%~84.0%;总酚含量和抗氧化活性烹调后显著增加,总酚含量的真实保存率、1,1-二苯基-2-三硝基苯肼自由基清除能力的真实保存率、铁离子还原能力的真实保存率分别为97.7%~130.6%、156.76%~203.79%、156.94%~172.53%;除煮制使青椒可溶性固形物含量显著降低22.06%,其他几种烹调方式可以很好地保存可溶性固形物。烹调还会使亚硝酸盐含量显著降低6%~18%,更利于人体健康。在统一烹调标准下,不同烹调方式对VC含量影响无显著差异,炒制较其他几种方式相比能更多地增加总酚含量,蒸制和煮制能更多地增加抗氧化活性,煮制可以更多地减少亚硝酸盐的含量。综合而言,蒸制处理的青椒能更好地保持青椒的营养品质,且显著降低亚硝酸盐含量,更利于人体健康,建议对青椒的食用以蒸制处理后食用为好。在24 h模拟配送过程中,烹调青椒的营养品质呈下降趋势,亚硝酸盐含量呈缓慢上升趋势;蒸制和微波处理的青椒品质变化相对缓慢,更适宜作为模拟冷配送的前处理过程;营养物质在前8 h内快速下降,亚硝酸盐含量在模拟配送24 h显著增加,建议以青椒为原料的餐饮冷藏配送时间不宜超过24 h,且应在前8 h内采取保护措施。     

Effect of sand roasting and microwave cooking on antioxidant activity of barley

Eight different barley cultivars were roasted in sand and cooked in a microwave oven and evaluated for antioxidant activity (AOA), total phenolic content (TPC), non-enzymatic browning, polyphenol oxidase activity (PPO), total flavonoid content (TFC), reducing power and metal chelating activity. Sand roasting resulted in higher puffing index. Greater increase in yellowness of the roasted flour was brought about by microwave cooking. A significant decrease in TPC (8.5 to 49.6%) and TFC (24.5 to 53.2%) was observed after roasting. The AOA significantly increased (16.8 to 108.2%) after roasting with sand roasted barley exhibiting higher AOA. The reducing power and metal chelating activity significantly increased by up to 77.5% and 78.9%, respectively after roasting with sand roasted samples showing greater effect. The non-enzymatic browning index increased (315 to 774%) and was higher for sand roasted barley. The microwave cooking brought about a greater reduction (45.1 to 76.8%) in PPO activity.     

中式烹饪对紫甘蓝的抗氧化物质和抗氧化活性的影响

研究了不同的中式烹饪方式(煮、汽蒸、微波、炒和油炸)对紫甘蓝的抗氧化物质(花色苷、类胡萝卜素、维生素C和酚类)和抗氧化性的影响。与生紫甘蓝相比,总硫苷、总类胡萝卜素、维生素C和总酚的含量以及抗氧化性在中式烹饪后都明显降低。其中,炒和油炸导致抗氧化物质和抗氧化性的显著减少,而汽蒸和微波保留了最多的促进健康的化合物,是烹饪紫甘蓝的最好方式。延长烹饪时间会引起抗氧化物质和抗氧化性的更多损失。抗氧化物质和抗氧化活性的相关性研究表明:维生素C与抗氧化能力具有更多的相关性,而总类胡萝卜素含量与抗氧化能力具有最小的相关性。     

烹饪方式对红枣多酚抗氧化活性的影响

研究了不同烹饪方式(高压蒸、煮及常压蒸、煮)对红枣枣皮、枣肉中多酚粗提物及4种存在形式酚酸部分的总酚含量及抗氧化活性的影响。采用Folin-Ciocalteu比色法测定其总酚含量、DPPH法和FRAP法分别评价其抗氧化活性。结果表明:高压蒸煮较常压处理红枣中的总酚含量较高,尤其是枣肉;常压煮制红枣的枣皮和枣肉中酚酸类化合物的总酚含量均最高。常压蒸制处理的红枣枣皮的DPPH·清除能力和总抗氧化能力均较强,而高压蒸制处理的红枣枣肉的DPPH·清除能力较强,常压煮制的红枣枣肉总抗氧化能力较强。红枣中总酚尤其是酚酸类化合物对其抗氧化活性起了很大的作用。红枣若采用高压烹饪方式,蒸制处理能较好地保存红枣中的酚类化合物及抗氧化活性;若采用常压烹饪方式,则煮制较好。     

不同烹饪方式的羊肚菌在体外消化过程中营养成分溶出差异比较

为研究不同烹饪方式对羊肚菌营养品质的影响,采用体外消化方法对煮制、蒸制以及烤制处理的不同粒度羊肚菌粉（粗粉、超微粉）进行消化。比较了消化后的羊肚菌粉显微形态,模拟胃、肠消化液中还原糖、蛋白质、游离氨基酸、总酚含量以及DPPH（1,1-Diphenryl-2-Picrylhydrazyl）自由基清除能力、铁离子还原能力（Ferric Ion Reducing Antioxidantpower,FRAP）、阳离子自由基清除能力2-azinobis-（3-ethylbenzthiazoline-6-sulfphonate,ABTS）。结果表明：经过体外胃、肠消化后,烤制处理的羊肚菌粉还原糖、蛋白质、多酚溶出量最高,蒸制其次,煮制最低,烤制比煮制平均依次高62.87%、58.58%、4.69倍;蒸制处理的羊肚菌,溶出的游离氨基酸含量在所有处理中最高,粗粉、细粉平均为40.40 mg/g,分别比烤制、蒸制高出18.77%,19.81%。超微粉碎不能有效提高还原糖、多酚的溶出,但可以显著提高蛋白质、游离氨基酸的溶出（P<0.05）;模拟消化液的DPPH值没有显著差异,但FRAP和ABTS值差异显著（P<0.05）,烤制处理的最高,其次是蒸制,煮制最低;超微粉碎不能有效提升羊肚菌模拟消化液的抗氧化水平。该研究为羊肚菌的科学食用提供了参考。     

不同热处理方法对芦蒿抗氧化活性的影响

对芦蒿分别进行蒸、煮和微波加热处理,用DPPH法测定它们的抗氧化活性,并与热处理前的新鲜芦蒿的抗氧化活性进行比较,发现不同热处理方法对芦蒿的抗氧化活性的影响不同。总体上看,芦蒿的抗氧化能力变化较大,新鲜芦蒿抗氧化能力较低,热处理后抗氧化能力大幅度升高。本实验专门就一系列不同浓度、不同热处理后的芦蒿进行研究,并与合成抗氧化剂BHT比较,结果表明,经微波加热处理后芦蒿的抗氧化能力很强,0.333g湿重的芦蒿经微波加热后的抗氧化能力就相当于1mgBHT纯品的抗氧化能力。     

煮制工艺对中国对虾品质的影响

以多酚氧化酶相对酶活力、水分含量、持水力、虾青素含量、蛋白质含量及提取率、色差、质构、感官评分和扫描电镜等为指标,研究不同煮制工艺(柠檬酸质量浓度和煮制时间)对中国对虾品质的影响。结果表明,随着柠檬酸质量浓度的提高,虾头中多酚氧化酶完全失活的时间逐渐缩短,但柠檬酸质量浓度过高不利于虾体口感,故确定其最优质量浓度为4 g/L。随着煮制时间的延长,虾体中水分含量和持水力均逐渐下降,虾青素含量先上升后下降,总蛋白含量不断下降,其中肌原纤维蛋白和肌浆蛋白在煮制2 min时已大部分变性。煮制过程中,虾体L*值和a*值先升后降,b*值不断上升,硬度、内聚性和咀嚼性不断升高,弹性不断下降。感官评价结果显示,煮制4 min对虾各个单项评分最高,其感官总评分最高。扫描电镜结果表明,煮制过程中对虾肌纤维因受热逐渐发生变性,导致其整齐度下降、纤缝隙增大、维断裂程度加剧。综合上述指标,确定最佳煮制时间为4 min。本研究成果可为虾类制品生产企业完善生产工艺、提升产品品质提供理论依据。     

基于营养与智能感官综合比较不同烹饪方式下芫根的品质差异

为筛选出芫根的适宜烹饪方式,本研究利用氨基酸自动分析仪、电子舌和食品热量检测仪（Calory Answer）比较了5种烹饪方式（水煮、气蒸、微波、高压和油炒）下芫根游离氨基酸、整体滋味和营养成分的差异,同时对芫根的抗氧化活性进行了分析。结果表明：新鲜芫根中总游离氨基酸含量为261.06 mg/100 g,以甜味氨基酸为主,气蒸、微波和油炒后芫根中总游离氨基酸的含量分别提高90.50%、59.74%和83.92%,其中苦味氨基酸比例增加;水煮能够增加酸味和鲜味氨基酸的比例,减少苦味氨基酸比例。油炒、微波和高压能显著提高芫根的能量和碳水化合物含量,气蒸和油炒能显著提高其多酚含量和抗氧化活性（P<0.05）。电子舌能有效区分不同方式烹饪的芫根,水煮和气蒸的芫根滋味较为接近,微波和高压的相似,油炒的较其他相比滋味差异较大。主成分综合评价分析表明：芫根最适宜的烹饪方式是气蒸,其次是油炒。     

Effects of boiling and microwaving treatments on nutritional characteristics and antioxidant activities of Agaricus blazei Murril

The effects of boiling and microwaving on nutritional compositions, antioxidant components and antioxidant activities of fresh and frozen A. blazei Murril (AbM) were evaluated and compared. The results showed that the contents of crude protein, ash, total soluble protein, total soluble sugar, vitamin C, and total phenolics decreased by both cooking treatments, but no significant changes were observed in lipids. Amino acid composition analysis showed that the ratio of total essential amino acids to total amino acids increased, and the ratio of total non‐essential amino acids to total amino acids thus decreased by both cooking treatments. Boiling and microwaving significantly decreased the contents of glucose, galactose and mannose, and the effect of boiling was higher than that of microwaving. Furthermore, boiling and microwaving significantly decreased the DPPH‐scavenging activity and reducing power of AbM. Analysis of the relations between the antioxidant activities and total phenolic concentrations testified that the cooking treatments not only decreased the total phenolic contents, but also changed the types and relative amounts of phenolic compounds of AbM.     

The antioxidant activity and composition of fresh, frozen, jarred and canned vegetables

Regular consumption of dietary antioxidants may reduce the risk of several serious diseases. As vegetables are a major source of antioxidants it is desirable to assess their antioxidant activity and compare different processing and preparation methods. The total antioxidant activity was determined in water- and lipid-soluble extracts from fresh, stored and frozen vegetables. The contribution of individual compounds to total antioxidant activity was estimated. In stored vegetables at ambient or chill temperatures antioxidant activity declined. Blanching and freezing of peas and spinach reduced water-soluble antioxidant activity by 30 and 50%, respectively, thereafter levels remained constant on storage at −20 °C. Samples of frozen peas and spinach purchased from retail outlets had substantially higher antioxidant activity than canned or jarred samples. In a comparison of cooking methods, microwave and boiling for short periods had a negligible effect on total antioxidant activity, but substantial losses occurred after prolonged boiling in water.     

水煮和微波处理对巴西蘑菇营养品质及抗氧化能力的影响

研究了水煮和微波加热处理对新鲜巴西蘑菇营养成分及其抗氧化能力的影响。结果表明,水煮和微波加热处理不同程度上降低了总蛋白质、灰分、可溶性蛋白质、可溶性多糖、总酚和VC的含量,而对脂肪的含量没有显著性变化。另外,加热处理明显改变了巴西蘑菇氨基酸和单糖的组成,微波处理的损失率显著低于水煮处理。加热处理对巴西蘑菇的还原力和清除DPPH·能力的影响显示,水煮和微波处理不仅降低了巴西蘑菇总酚含量,而且改变了其总酚的组成,水煮处理对其抗氧化能力的破坏能力明显高于微波处理。研究可为消费者日常生活合理烹调巴西蘑菇提供科学依据。     

不同加工方式对青稞中酚类物质的影响

为探明不同加工方式对青稞全谷物中酚类物质的影响,最大程度地保留抗氧化和降血糖活性物质。以海南昆仑17号青稞籽粒为实验材料,分别采用蒸制、煮制、炒制、微波、烤制、空气炸锅等六种加工方式对青稞籽粒进行热加工处理,分析加工前后青稞中游离多酚、结合多酚、游离黄酮和结合黄酮的含量,以及抗氧化和降血糖活性的变化。结果表明,不同加工方式制备的青稞多酚和黄酮含量存在一定程度上的差异。与未加工相比,其他加工方式所得青稞游离多酚和游离黄酮的含量均显著降低（P<0.05）（除炒制外）,结合多酚和结合黄酮的含量均升高。与未加工相比,蒸制和煮制的方式对青稞游离多酚含量的损失高达43.77%和67.85%,炒制使青稞结合黄酮含量增加38.10%。此外,不同加工方式的青稞多酚提取物具有较好的DPPH自由基清除能力和α-葡萄糖苷酶抑制活性,且清除和抑制能力在一定浓度范围内具有浓度依赖性。在六种加工方式中,炒制处理青稞游离和结合多酚提取物（5 mg/mL）的DPPH自由基清除率最高,分别为70.01%、54.52%,且其α-葡萄糖苷酶抑制率也最高,分别为84.84%、75.70%。因此,炒制处理可较好地保留热加工前全谷物青稞中酚类物质的含量,从而发挥抗氧化和降血糖作用。     

蒸煮方式对熟制小龙虾尾肉解冻后品质的影响

采用4 种蒸煮方式（以冷水开始煮制（BC）、以沸水开始煮制（BB）、以冷水开始蒸制（SC）和以沸水开始蒸制（SB））对小龙虾进行熟制,然后将熟制小龙虾于－18 ℃冻藏30 d,再采用2 种解冻方式（静水解冻（thawing in still water,ST）和4 ℃低温解冻（low temperature thawing,LT））进行解冻,研究不同解冻和蒸煮方式对小龙虾肌肉品质的影响。以冷却至室温未经冻藏的熟制小龙虾肉为对照组。测定菌落总数、持水性、水分分布、质构特性、色度、硫代巴比妥酸反应物（thiobarbituric acid reactive substances,TBARs）值,并通过电子鼻分析和感官评价分析小龙虾肉的感官特性。结果表明：ST组中采用BC和SC蒸煮小龙虾肉的菌落总数最高,分别为4.26、4.43（lg（CFU/g））;ST组较LT组更易使小龙虾肉的水分流失,并且以冷水开始蒸煮（BC和SC）的小龙虾肉持水性优于以沸水开始蒸煮（BB和SB）的小龙虾。感官评价与质构分析的结果表明,以沸水开始蒸煮的小龙虾肉感官品质更优。与对照组相比,ST与LT组小龙虾肉亮度值、黄度值（b*）增大,红度值减小,ST组中BC、BB、SC、SB方式蒸煮小龙虾肉的b*分别为32.67、28.87、33.36、27.36,显著高于其他2 组;ST组比LT组氧化程度高,且以冷水开始蒸煮的小龙虾肉脂肪氧化程度大于以沸水开始蒸煮的小龙虾。2 种解冻方式的小龙虾肉气味差异明显,冷、热水蒸煮对小龙虾的气味影响较大。