The effect of cooking on Brassica vegetables

Assessing antioxidant intake requires a food antioxidant database. However, cooking may affect antioxidant content due to antioxidant release, destruction or creation of redox-active metabolites. Here, effects of boiling, steaming and microwaving of broccoli, cauliflower, cabbage and choy-sum (Chinese cabbage) were explored by measuring antioxidant contents of raw and cooked vegetables. Cooking water was also tested. For all cooked vegetables, antioxidant content was highest in steamed > boiled > microwaved, and decreased with longer cooking time, regardless of method. All steamed vegetables had higher antioxidant contents than had matching raw vegetables. Effects were variable for boiling and microwaving. Microwaving caused greater antioxidant loss into cooking water than did boiling. Marked losses of anitoxidants occurred in microwaved cabbage and spinach. To assess food antioxidant content/intake accurately, cooking effects need detailed study. Steaming may be the cooking method of choice to release/conserve antioxidants. The cooking water is a potentially rich source of dietary antioxidants.     

Effect of cooking method on water absorption and ease of dehulling in preparation of African locust beans for Iru

Gas boiling or pressure cooking increased the level of water uptake by locust beans over that with firewood cooking, mainly because of sustained heat input. Presoaking in cold water produced no advantage. The boiling times necessary for satisfactory dehulling were 10h using firewood, 6h by gas boiling, and 30 and 50min respectively by pressure cooking at 121 and 115°C.     

The effects of domestic cooking on the levels of 3-monochloropropanediol in foods

The results are reported of a study to determine the effect of domestic cooking procedures on the level of 3-monochloropropane-1,2-diol (3-MCPD) in selected foods. Samples of 23 foods comprising stock cubes, gravies, a cake mix, batters, breads, cheese and meats were subjected to a range of cooking procedures including grilling, toasting and microwaving. The resulting levels of 3-MCPD were compared with those present in the foods before cooking. Grilling and toasting produced substantial increases in the 3-MCPD content of bread, forming up to 0.3mg/kg, and of most cheeses, resulting in levels of up to about 0.1mg/kg. Microwave cooking produced elevated 3-MCPD levels in some cheeses. Frying laboratoryproduced batters increased 3-MCPD levels to about 0.1mg/kg whereas a retail batter contained no detectable 3-MCPD when fried. The remaining foods showed little or no discernible increase on cooking.     

植物甾醇的提取、生理功能及在食品中的 应用综述

本文主要介绍了植物甾醇的相关性质、功能及在食品中的应用等。综述了在油脂加工副产物中甾醇的含量与提取：包括在副产物油脚中甾醇的含量与提取率;不同来源的副产物脱臭馏出物中甾醇的含量、主要甾醇成分及提取工艺等。介绍了植物甾醇的特殊功能（如降低胆固醇、减少冠心病发生、抗氧化等）及在食品中的广泛应用。天然植物甾醇常在食品体系中添加时出现结晶现象,且在水相和油相中溶解度低,为能在食品中广泛应用,常采用植物甾醇改性将其转变成甾醇酯的方式添加到食品中。文中介绍了植物甾醇改性的不同工艺并得到了较好的效果。在特殊的环境条件下,天然甾醇会发生氧化产生甾醇氧化产物。文中介绍了不同储藏条件甾醇氧化产物的含量及主要成分、甾醇氧化稳定性与结构的关系以及对主要慢性病的发生和发展的促进作用等。     

Catalytic determination of traces of oxalic acid in vegetables and water samples using a novel optode

A new optode has been introduced for determination of oxalic acid. The optode sensing reagent is Victoria blue 4R which is immobilized on triacetylcellulose membrane. This reagent could be oxidized by dichromate in acidic media resulting in decoloration of the membrane. Oxalic acid has a strong catalytic effect on this reaction. The difference in absorbance of the immobilized form of Victoria blue 4R at 615 nm between uncatalyzed and catalyzed reactions (ΔA) is directly proportional to the concentration of oxalic acid. Oxalic acid can be determined in the concentration range of 2–180 μg ml⁻¹. The effect of different possible interfering species has been examined and was shown that the optode has a very good selectivity. The optode has been applied for the determination of oxalic acid in different real samples such as spinach, beet root, mushroom and river water with excellent recoveries.     

Water sorption and cooking time of red kidney beans (Phaseolus vulgaris L.): part I – Effect of freezing and drying conditions on water sorption and cooking time

Water sorption and cooking time of kidney beans were determined. The beans were manually harvested at 19.2 ± 0.1% moisture content and stored at ?20 and ?10 °C for about half a year. The beans were further dried at 30, 40 and 50 °C inside a thin‐layer drier for 7.5 h or under room conditions for 4 week. The freezing storage temperature before the beans were dried did not influence their cooking time and water sorption. The saturated kernel volumes decreased approximately 7% after drying. The beans decreased their sphericity during water sorption and had a larger swelling ratio in the thickness direction than in other directions. Lower initial moisture content, especially with a higher drying temperature, decreased water sorptivity and resulted in higher percentage of uncooked kernels if the beans were not soaked before cooking. However, there was no relationship between initial moisture content and uncooked percentage if the beans were soaked before cooking. High drying temperature resulted in hard‐to‐cook (HTC) phenomenon.     

植物甾醇对压缩饼干货架寿命的影响

运用加速实验研究植物甾醇对压缩饼干货架寿命的影响。将植物甾醇添加到压缩饼干中,通过分析测试60、70℃和80℃下压缩饼干酸值的变化,利用Arrhenius方程建立储藏温度与酸值的反应关系,验证植物甾醇对压缩饼干货架寿命的影响。结果表明:25℃时,甾醇组的压缩饼干货架寿命为1 594.7 d,空白组压缩饼干货架寿命为1 337.8 d,货架寿命延长了19.2%。植物甾醇能够在一定程度上延长压缩饼干的货架寿命。     

Effect of cooking bag and netting packaging on the quality of pork ham during water cooking

As a preliminary test for combining water cooking with vacuum cooling in soup of pork ham, three package treatments were designed to study the effect of cooking bag and netting on the quality of water cooked ham, i.e. ham cooked with a cooking bag and without a cooking bag (single netting and double netting). For treatments without a cooking bag, the results indicated that there was no significant superiority of ham cooked with double netting compared with ham cooked with single netting on the processing efficiency and quality characteristics. Although the hams cooked with a bag performed better in some chemical retentions and pigment, the water contents were significantly lower than those hams cooked in single netting (P<0.05), and there was a higher shrinkage tendency compared with the hams cooked without a bag. For the processing characteristics and texture properties of pork ham, there were no significant differences observed among the treatments with and without a cooking bag in terms of the combined effect of cooking and cooling (P>0.05). By considering the safety, convenience, cost, and the recovery effect on the quality changes of ham during vacuum cooling in soup, cooking with single netting is a better choice for future research.     

栀子甾醇的分离分析

本文对栀子的植物甾醇成分进行分离分析,以期扩大栀子的应用范围。文中用索氏提取法从栀子中提取出果油,得率为16.7%。通过皂化法,用乙醚萃取出果油中的粗甾醇,再以溶剂结晶法对粗甾醇进行纯化。最后对所得甾醇样品的组分采用HPLC-MS分析。结果表明,栀子果油中可能含有β-谷甾醇和甘氨胆酸等甾醇成分。     

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。      

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.     

植物甾醇共轭亚油酸的制备及其血脂调节作用的研究

植物甾醇与共轭亚油酸甲酯通过酯交换反应合成植物甾醇共轭亚油酸脂,反应产率达94%,该法适合工业化生产。首次研究了植物甾醇共轭亚油酸酯对大鼠血脂的调节作用,实验表明植物甾醇共轭亚油酸酯具有调节血脂作用。     

烹调对蔬菜中烟酸含量的影响

为研究不同烹调方法对蔬菜中烟酸含量的影响，对7种蔬菜(白萝卜、胡萝卜、豇豆、扁豆、茄子、土豆、菠菜)采用6种不同烹调方法(炒、炖、腌、蒸、焯、炸)进行处理，用微生物法测定其鲜样和烹调后样品的烟酸含量。以烹调至可食用状态为标准进行比较。蔬菜经6种不同烹调方法处理后，其烟酸保存率大部分在60％以上。经过炒、炖处理后的蔬菜中烟酸保存率较高；经过焯和大量失去水分的腌，蔬菜中烟酸保存率较低。其中炸扁豆、炒胡萝卜、炒茄子烟酸含量与其鲜样相比差异无显性意义(P＞0．05)，其它烹调后样品烟酸含量与未处理的鲜样比较差异均有显性意义(P＜0．01)。本研究结果对食品工业加工方法具有指导意义和参考价值。     

Effect of Cooking on Soluble and Insoluble Oxalate Contents in Selected Pakistani Vegetables and Beans

The present study evaluated the effects of cooking on the total, soluble and insoluble oxalate contents in six different types of locally consumed vegetables and beans (spinach, carrots, beet root, white bean, red bean and soybean). The foods were cooked in water until they reached the soft consistency (12–15 min for vegetable and 2 h for beans). The raw and cooked samples were analyzed for their soluble and insoluble oxalate contents using the HPLC techniques. The total oxalate content of raw spinach, carrot, beet root, white bean, red bean and soybean, were found to be 978 ± 5, 49 ± 7, 67 ± 12, 158 ± 16, 113 ± 15, and 497 ± 22 mg/100 g of fresh weight respectively. The total oxalate contents of these foods after boiling were 477 ± 8, 16 ± 9, 52 ± 14, 47 ± 17, 72 ± 17, and 224 ± 25 mg/100 g of fresh weight respectively. The results showed that boiling significantly (P < 0.05) reduced both soluble and insoluble oxalate contents. More losses were observed in the soluble than the insoluble oxalates. The reduction in soluble oxalate in different vegetables ranged from 16 to 66% whereas in beans ranged from 40 to 77%. The data suggests that the use of boiled vegetables can be an effective strategy for reducing the dietary intake of oxalates in individuals predisposed to the development of kidney stones.     

Effects of increasing levels of transglutaminase on cooking quality of bran supplemented spaghetti

This study investigated the possibility of incorporating high levels of bran into spaghetti formulation by using transglutaminase (TG)—catalyzed crosslinking, without deterioration in spaghetti quality. Two durum wheat samples and one bread wheat sample were milled to semolina or farina. Ground mixture of coarse and fine brans of each cultivar was substituted for a portion of semolina or farina obtained from the respective cultivar, at the levels of 15 and 30% and then processed into spaghetti. Bacterial TG was added to the spaghetti formula at the levels of 0.2% and 0.4% (w/w). The results indicated that the TOM values and the sensory characteristics of the spaghetti were generally affected by the cultivar, bran supplementation, and TG addition level. The samples with TG exhibited significantly lower scores for TOM and higher sensory scores for firmness, stickiness, and bulkiness when compared with the respective control sample of each cultivar. As a result, transglutaminase addition had a significant improving effect on spaghetti quality which was more obvious in the weaker cultivar and it was possible to overcome the deteriorative effects of bran on spaghetti quality.     

Effect of roasting conditions and grinding on free radical contents of coffee beans stored in air

The influence of roasting and storage conditions on free radical contents of individual Arabica coffee beans was examined during storage of whole, half and ground beans in air over a 1-month period. Free radical contents increased with increasing roasting time (roasting degree), but the atmosphere (air vs. N₂) used in the roasting and cooling process had little effect. There was a progressive increase in free radical contents with storage time, but the rate was much lower in whole beans than with half and fully ground beans, for which the rate was similar. These results suggest that exposure to O₂, rather than physical grinding is the main mechanism for storage-related free radical generation, and strongly indicate that roasted coffee is best kept as whole beans in order to minimise changes during prolonged periods of aerobic storage. Furthermore, they demonstrate that EPR measurements can contribute to understanding the process and storage related changes in coffee.     

不同类型植物甾醇对肉鸭生长及肌肉品质的影响

旨在研究不同类型植物甾醇对肉鸭生产性能、体脂沉积、体成分及肌肉品质的影响。选用1日龄樱桃谷肉鸭540只,随机分为3组,每组6个重复,每重复30只,分别饲喂以下3种日粮:(1)对照组(C):基础日粮;(2)试验1组(Ⅰ):基础日粮+20 mg.kg-1植物甾醇A;(3)试验2组(Ⅱ):基础日粮+20 mg.kg-1植物甾醇B,饲养时间为42 d。结果表明:日粮中添加不同类型植物甾醇均极显著降低前期料重比(P<0.01);与植物甾醇A相比,日粮中添加植物甾醇B极显著增加了21 d平均体重和前期平均日增重(P<0.01),但极显著降低后期平均日增重(P<0.01);日粮中添加植物甾醇A和植物甾醇B,均能显著降低肝脏中胆固醇的含量,分别降低了15.92%(P<0.05)和24.57%(P=0.01);日粮中添加植物甾醇A极显著降低肉鸭胸肌的滴水损失(24 h和48 h)(P<0.01);日粮中添加20 mg.kg-1不同类型植物甾醇对肉鸭的肌间脂肪厚度、皮下脂肪厚度、水分、粗脂肪、粗蛋白、pH均无显著影响(P>0.05)。结果提示,日粮中添加植物甾醇A和植物甾醇B均能降低肉鸭肝脏胆固醇的含量,且前期添加植物甾醇B、后期添加植物甾醇A更有利于肉鸭的生长;植物甾醇A能够在一定程度上改善鸭肉品质。     

植物甾醇制取及应用研究进展

油脂中植物甾醇含量较少,但是却有着重要的生理功能。主要围绕国内外近年来植物甾醇的制取及应用方面的研究进展进行综述。介绍了油脂精炼过程中植物甾醇在各工段的损失情况;对脱臭馏出物(DD油)、酸化油、渣油为原料的植物甾醇制取工艺及甾醇酯的合成工艺发展现状进行论述;对植物甾醇的应用进行了介绍。以期为植物甾醇的生产及应用提供技术参考。     

Ingredient composition and pasta:water cooking ratio affect cooking properties of nontraditional spaghetti

An experiment was conducted to determine the effect of different pasta:water ratios and nontraditional ingredients on the cooking properties of spaghetti. Spaghetti was made using semolina and semolina containing 20% (w/w) nontraditional (NT) ingredients (corn, flaxseed, lentil, oat, pinto bean and soybean flours). Pasta:water ratios evaluated were 13 g:400 mL, 27 g:400 mL and 48 g:400 mL. Addition of pasta caused a decline in cooking water temperature. The water temperature drop and recovery time to boiling (100 °C) varied with pasta:water ratio and with nontraditional ingredient in the spaghetti. These results were attributed to the calculated specific heat capacity of the ingredients incorporated in the spaghetti. Cooking time was reduced for all NT spaghetti with respect to the control sample and was longest when 48 g of pasta was cooked. Pasta:water ratio affected cooking loss but not cooked weight or cooked firmness. Cooking losses were greater with 13 g:400 mL compared to 48 g:400 mL.