NUTRIENT QUALITY OF SELECTED VEGETABLES PREPARED BY CONVENTIONAL AND COOK-FREEZE METHODS

Selected vegetables (spinach, broccoli, sweet potatoes, and collard greens) prepared in 2.27 kg (5 lb) quantities by boiling, were frozen and stored for six months at ?18°C. Zinc, iron, β-carotene, and ascorbic acid were determined on the raw vegetable immediately after cooking and after reheating in a microwave oven subsequent to 6 months frozen storage. The greatest nutrient loss occurred for water soluble nutrients during boiling. Nutrient comparison between cooked samples (conventional method) and samples microwaved after 6 months frozen storage (cook-freeze method) indicated that differences existed only in ascorbic acid content of spinach. Data indicated that vegetables prepared by cook-freeze, a method used by health care institutions, were generally equal in nutrient quality to conventionally prepared vegetables.     

Effects of Cooking in Solutions of Varying pH on the Dietary Fiber Components of Vegetables

To study the effect of pH on dietary fiber components of vegetables, beans, cauliflower, potatoes, peas and corn were cooked in buffers of pH 2, 4, 6, and 10. Water-soluble pectin and hemicellulose, water-insoluble pectin and hemicellulose, cellulose and lignin were quantitated in raw, cooked vegetables and cooking medium. Tenderness and pH of raw and cooked vegetables were determined. Texture varied with cooking medium. Cooked vegetables were most firm at pH 4 and softest at pH 10. Dietary components found in cooking medium reflected these textural changes. Vegetables which showed greater pH effects exhibited greater changes in fiber components.     

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.     

三种烹饪方式对蔬菜中维生素C含量的影响研究

目的:比较3种烹饪方式对8种蔬菜中维生素C含量的影响。方法:选取8种常见蔬菜,分别采用较新型烹饪方式(不锈钢炒锅加盖密闭式)、模拟传统烹饪方式(不锈钢炒锅不加盖)与传统烹饪方式(铁锅急火快炒不加盖)进行烹调,不添加食盐仅添加烹调油,严格控制其它烹饪条件。采用GB/T 5009.86—2003 2,4—二硝基苯肼法测定烹饪前后8种蔬菜中维生素C含量的变化。结果:相同条件下,采用3种不同烹饪方式对同种蔬菜进行烹调的结果显示,不同烹调方式都会造成蔬菜中维生素C损失,且维生素C含量与烹饪前相比,差异具有统计学意义(P<0.05)。新型烹饪方式与传统烹饪方式相比,蔬菜中维生素C含量较高,且据有显著性差异(P<0.05),新型烹饪方式组蔬菜中维生素C保存率最高(8种蔬菜分别为58.52%、73.21%、85.14%、68.66%、87.17%、82.78%、44.54%、74.91%);传统烹饪方式组蔬菜中维生素C保存率最低(对应上述8种蔬菜分别为29.26%、61.91%、52.58%、38.53%、43.58%、59.60%、24.66%、40.62%)。结论:不同烹饪方式对蔬菜中维生素C损失影响不同,新型烹饪方式对蔬菜中维生素C损失最小,保存率最高。     

Vitamin C,total phenolics and antioxidative activity in tip‐cut green beans (Phaseolus vulgaris) and swede rods (Brassica napus var. napobrassica) processed by methods used in catering

BACKGROUND: Retention of nutrients in vegetables during blanching/freezing, cooking and warm‐holding is crucial in the preparation of both standard and therapeutic diets. In the present study, conventional cooking in water, and cooking by pouch technology (boil‐in‐bag, sous vide) were compared in their ability to retain vitamin C, total phenolics and antioxidative activity (DPPH and FRAP) in industrially blanched/frozen tip‐cut green beans and swede rods. RESULTS: After conventional cooking, 50.4% total ascorbic acid, 76.7% total phenolics, 55.7% DPPH and 59.0% FRAP were recovered in the drained beans. After boil‐in‐bag cooking, significantly (P < 0.05) higher recoveries were obtained, i.e. 80.5% total ascorbic acid, 89.2% total phenolics, 94.8% DPPH and 92.9% FRAP. Recoveries after sous vide cooking were comparable to those of boil‐in‐bag cooking. By conventional cooking, 13.5–42.8% of the nutrients leaked into the cooking water; by sous vide about 10% leaked to the exuded liquid, while no leakage occurred by boil‐in‐bag cooking. Warm‐holding beans after cooking reduced recoveries in all components. Recoveries in swede rods were comparable but overall slightly lower. CONCLUSION: Industrially blanched/frozen vegetables should preferably be cooked by pouch technology, rather than conventional cooking in water. Including cooking water or exuded liquid into the final dish will increase the level of nutrients in a meal. Warm‐holding of vegetables after cooking should be avoided. Copyright © 2010 Society of Chemical Industry     

Folacin and Ascorbic Acid Retention in Fresh Raw, Microwave, and Conventionally Cooked Spinach

Fresh spinach was assayed for total folacin and reduced ascorbic acid content, before and after cooking by a microwave and conventional method. Mean ascorbic acid content of raw, microwave cooked and conventionally cooked spinach was 26.5 mg/lOOg, 13.5 mg/l00g, and 17.0 mg/lOOg, respectively. Ascorbic acid content was decreased significantly by both cooking methods; retention was 47% in microwave and 51% in conventionally cooked spinach. Total folacin content of raw, microwave, and conventionally cooked spinach was 161 mcg/lOOg, 183 mcg/lOOg, and 157 mcg/lOOg, respectively. Retention of folate was 77% in conventionally cooked and 101% in microwave cooked spinach.     

Effect of different cooking methods on the content of vitamins and true retention in selected vegetables

This study evaluated the effect of different cooking methods including blanching, boiling, microwaving and steaming on the content of vitamins in vegetables. True retention was estimated using the yield expressed as a ratio of the weight of the cooked sample to the weight of the raw sample. The retention of vitamin C ranged from 0.0 to 91.1% for all cooked samples. Generally, higher retention of vitamin C was observed after microwaving with the lowest retention recorded after boiling. Cooked vegetables were occasionally higher contents of fat-soluble vitamins, including α-tocopherol and β-carotene, than that of their fresh counterparts, but it depends on the type of vegetables. Microwave cooking caused the greatest loss of vitamin K in crown daisy and mallow; in contrast, it caused the least loss of vitamin K in spinach and chard. Cooking may cause changes to the contents of vitamins, but it depends on vegetables and cooking processes.     

Effects of storage condition and domestic cooking on the quality and nutrient content of African leafy vegetables (Cassia tora and Corchorus tridens)

BACKGROUND: The main objective of this research was to determine changes in nutrient content of two African leafy vegetables, Cassia tora and Corchorus tridens, on cooking and storage under different temperature conditions, i.e. room storage (20 °C), refrigerated storage (4 °C) and frozen storage (?18 °C). RESULTS: The leafy vegetables were analysed for moisture, colour (Hunter L, a, b), texture, total chlorophyll, ascorbic acid, dehydroascorbic acid and total phenolics. Results indicated that the degradation of ascorbic acid was highest as a result of frozen storage, followed by room temperature storage. The dehydroascorbic acid content was correspondingly high in frozen stored leafy vegetables, whereas it was undetectable in the room temperature and refrigerated stored materials. The total phenolic content of the leaves increased with storage time while the total chlorophyll content decreased under all storage conditions. Domestic cooking resulted in significant additional losses of ascorbic acid following storage under all temperature conditions, with only 1–10% retention in the leaves and 50–60% retention in the cooking water. The green colour of the leafy vegetables was retained best under refrigerated and frozen storage, while the peak force and toughness of the leaves increased upon storage under all conditions. The moisture content of the leafy vegetables did not show any significant difference on storage. CONCLUSION: This study is one of few to report nutrient content changes on the same raw material stored under various temperature conditions and cooked domestically. Refrigerated storage resulted in the highest retention of ascorbic acid and green colour in the leafy vegetables. Copyright © 2009 Society of Chemical Industry     

Yield and Comparison of Nutritive and Energy Values: Pigs' Feet, Pigs' Tails

Raw and cooked pigs'feet and tails were compared for yield, proximate composition, mineral, vitamin, amino acid, protein efficiency ratio (PER) (calculated from amino acid compositions), saturated and polyunsaturated fats; and cholesterol content, The raw yields for pigs' feet and tails were 42.2 and 69.9%, respectively. Corresponding values for cooking losses were 9.4 and 13.0%. Cooking the two products resulted in significant increases in moisture content. Cooked pigs' feet produced significant losses of protein, fat, ash, and caloric values, while cooked pigs' tails showed none. Cooked pigs' feet and tails resulted in some changes in minerals, vitamins, amino acids, and polyunsaturated fat. There was no significant difference between the saturated fats and cholesterol in the raw and cooked products. The PER values of pigs' feet were lower than those of pigs' tails.     

Antioxidant and micronutrient quality of fruit and root vegetables from the Indian subcontinent and their comparative performance with green leafy vegetables and fruits

Commonly consumed, fruit vegetables (12) and root vegetables (15) in the Indian subcontinent in cooked and uncooked states assessed for inhibition of thiobarbituric acid reactive substances (TBARS), superoxide radical scavenging activity (SOSA), ferrous iron chelating ability (FICA) and nine micronutrients, exhibited large variability in these parameters. SOSA and FICA were significantly associated (r = 0.803, p < 0.001) with each other. Inhibition of TBARS showed marginal correlation with both FICA (0.38, p < 0.05) and SOSA (0.29, p > 0.05). There were significant cooking losses for each of the assessed antioxidant capacity parameters (p < 0.05). Contents of ascorbic acid, per 100 g of cooked fruit and root vegetables were high (61.9 and 31.3% of recommended daily allowance (RDA)). However, both the food classes were not good sources of beta‐carotene, riboflavin and thiamine (1.66–5.26% RDA). When compared with our data on 30 cooked green leafy vegetables (GLV) and 30 fresh fruits, root vegetables showed significantly (p < 0.05) higher levels of zinc and selenium. Cooked root vegetables were comparable with cooked GLVs but uncooked GLVs gave the highest values for inhibition of TBARS (0.73 ± 0.21 mM vitamin E/100g). SOSA (40.7 ± 15.6 mM tannic acid/100g) and FICA (41.6 ± 14.9 mM EDTA/100g) were highest for uncooked fruit vegetables. Root vegetables had the highest levels of polyphenols (251.4 ± 107.3 mg/100g). For the present study, popular fruits and vegetables such as guava, spinach, bitter gourd (Momordica charantia), yam, ginger and beetroot, and also less common ones like bael (Aegle marmelos), kokum (Garcinia indica) and mango‐ginger (Curcuma ameda), showed potential in vitro to combat oxidative stress. Copyright © 2005 Society of Chemical Industry     

Effect of cooking on total vitamin C contents and antioxidant activity of sweet chestnuts (Castanea sativa Mill.)

In this work the total vitamin C contents (ascorbic acid + dehydroascorbic acid) and antioxidant activity of raw and cooked chestnuts was evaluated. The vitamin C contents of raw chestnuts varied significantly between the different cultivars (cv) studied and it varied from 400 mg/kg dry weight (cv Lada) to 693 mg/kg dry weight (cv Martaínha). The different cultivars behave differently during the cooking process concerning the loss of vitamin C. A significant decrease in the vitamin C content of the chestnuts was observed, 25–54% for the boiling process and 2–77% for the roasting process. Boiled and roasted chestnuts can be good sources of vitamin C since it may represent 22.4%, 16.2%, 26.8% and 19.4%, respectively, of the recommended dietary intake for an adult man and woman. The cooking process significantly changed the antioxidant activity of the chestnuts. A difference was observed between the cultivars during the cooking processes, concerning the antioxidant activity. For the raw chestnuts the variation in vitamin C content of the chestnuts explains 99% of the antioxidant activity variation but for the roasted and boiled chestnuts this percentage significantly decreases to 51% and 88%, respectively. Although a high antioxidant activity is still present in the cooked chestnuts, the cause for this antioxidant activity is less dependent on the vitamin C content of the chestnuts, probably due to the conversion of ascorbic acid to dehydroascorbic acid. The increase in gallic acid during the cooking process, presumably transferred from the peels to the fruit, also contributes to the high antioxidant activity observed for the cooked chestnuts.     

Heating Cruciferous Vegetables Increases in Vitro Dialyzability of Intrinsic and Extrinsic Iron

Iron dialyzability (ID) from three Cruciferae (broccoli, kale and cabbage) was determined by an in vitro digestion method. The effect of added Crucifers on the ID of extrinsic nonheme iron as well as effects of heating were studied. Uncooked Crucifers contained iron of moderate ID (7–9%); cooking resulted in substantial ID increase (200%). Cooked Crucifers increased extrinsic ID three- to fourfold. Time and temperature relationships for the increase suggested that organic acids released after partial cell wall degradation combined with protein denaturation and iron solubilization from fiber were major reasons for differences between raw and cooked vegetables. Cruciferous vegetables can contribute to improved iron nutrition.     

Effect of water cooking on free phytosterol levels in beans and vegetables

Plant sterols (phytosterols) are known to decrease plasma cholesterol, mainly the atherogenic LDL cholesterol. In an earlier study, the thermal stability of phytosterols in vegetable oils was reported. The aim of this present work was to investigate the potential effect of cooking (30 min in boiling water), for eight plant products (broad bean, celery, cabbage, courgette, carrot, cauliflower, onion, pepper), on the free phytosterol level. Sitosterol was the most abundant sterol, followed by campesterol. After cooking, the level of total sterols was higher in all vegetables than that before cooking, if dry matter is considered. Acid hydrolysis (active for glycosylated phytosterols) yielded a higher sterol value than alkaline hydrolysis alone (active for esterified phytosterols). This indicated that studied vegetables contained appreciable amounts of steryl glycosides. Their cooking induced higher values of free phytosterols. Cooked vegetables could give better protection against cardiovascular diseases thanks to higher phytosterol levels.     

不同利用方式对几种根茎类蔬菜亚硝酸盐含量的影响

以山药、胡萝卜、莲藕为实验材料,研究不同贮藏条件、烹饪方法和熟菜保存方式下3种根茎类蔬菜中亚硝酸盐含量的变化。结果表明：无论常温还是低温贮藏,贮藏7d内,3种根茎类蔬菜的亚硝酸盐含量均呈现先增加后降低的趋势,虽然常温贮藏的亚硝酸盐含量高于低温贮藏,但两者均小于4mg/kg。不同烹饪加工可显著降低3种蔬菜的亚硝酸盐含量,煮制、炒制、烤制加工方式的亚硝酸盐含量降幅分别为70%～83%、66%～80%和33%～55%,其中胡萝卜的亚硝酸含量降幅最大,莲藕的最小。低温和常温保存的熟菜,菜体中亚硝酸盐含量随时间延长而增加,保存到48h时,3种菜体的亚硝酸盐含量均小于4mg/kg,且低温远低于常温(前者最大为1.03mg/kg,后者最大为1.98mg/kg),参照食用的亚硝酸盐标准,低温(4℃)和常温(20℃)保存的熟制根茎类蔬菜食用安全期均达48h,且煮制和炒制加工的熟菜优于烤制。     

Contribution of water and cooked rice to an estimation of the dietary intake of inorganic arsenic in a rural village of West Bengal, India

Arsenic contamination of rice plants by arsenic-polluted irrigation groundwater could result in high arsenic concentrations in cooked rice. The main objective of the study was to estimate the total and inorganic arsenic intakes in a rural population of West Bengal, India, through both drinking water and cooked rice. Simulated cooking of rice with different levels of arsenic species in the cooking water was carried out. The presence of arsenic in the cooking water was provided by four arsenic species (arsenite, arsenate, methylarsonate or dimethylarsinate) and at three total arsenic concentrations (50, 250 or 500 µg l^-1). The results show that the arsenic concentration in cooked rice is always higher than that in raw rice and range from 227 to 1642 µg kg^-1. The cooking process did not change the arsenic speciation in rice. Cooked rice contributed a mean of 41% to the daily intake of inorganic arsenic. The daily inorganic arsenic intakes for water plus rice were 229, 1024 and 2000 µg day^-1 for initial arsenic concentrations in the cooking water of 50, 250 and 500 µg arsenic l^-1, respectively, compared with the tolerable daily intake which is 150 µg day^-1.     

Contribution of water and cooked rice to an estimation of the dietary intake of inorganic arsenic in a rural village of West Bengal,India

Arsenic contamination of rice plants by arsenic-polluted irrigation groundwater could result in high arsenic concentrations in cooked rice. The main objective of the study was to estimate the total and inorganic arsenic intakes in a rural population of West Bengal, India, through both drinking water and cooked rice. Simulated cooking of rice with different levels of arsenic species in the cooking water was carried out. The presence of arsenic in the cooking water was provided by four arsenic species (arsenite, arsenate, methylarsonate or dimethylarsinate) and at three total arsenic concentrations (50,?250 or 500?µg?l^?1). The results show that the arsenic concentration in cooked rice is always higher than that in raw rice and range from 227 to 1642?µg?kg^?1. The cooking process did not change the arsenic speciation in rice. Cooked rice contributed a mean of 41% to the daily intake of inorganic arsenic. The daily inorganic arsenic intakes for water plus rice were 229, 1024 and 2000?µg?day^?1 for initial arsenic concentrations in the cooking water of 50, 250 and 500?µg?arsenic?l^?1, respectively, compared with the tolerable daily intake which is 150?µg?day^?1.     

江苏省农村家宴卫生现状调查

目的 掌握农村家宴的卫生现状，为卫生部门的监督管理提供依据。方法 采用问卷调查和现场检测的方法，对238家农村家宴进行卫生学调查。结果 农村家宴整体卫生水平较差，主要是加工场所布局不合理、卫生设施缺乏、生熟交叉污染、餐饮具不消毒以及民间厨师的个人卫生差等；抽检餐饮具大肠菌群合格率、砧板等表面洁净度合格率分别为44．20％和18．42％，经多因素Logistic回归分析，二者的合格情况均受多种因素的影响；蔬菜农药残留、熟肉制品微生物合格率分别为95．90％和64．52％，经尽形秩和检验显示，2～6月份其合格率有逐月降低趋势。结论 针对当前农村家宴的卫生现状，应对其加强科学的监管和指导。     

Nutrient retention in microwave cooked germinated legumes

The effects of germination on the cooking quality and nutrient retention in pressure and microwave-cooked Bengal gram, green gram and horse gram were studied. Ungerminated (UGL) and germinated legumes (GL) cooked in a microwave oven, and under pressure were analysed for moisture, protein, ash, iron, thiamin, ascorbic acid, in vitro protein digestibility (IVPD) and starch digestibility (IVSD) and bioavailable iron. Results revealed that microwave cooking required more water and time than did pressure cooking. The range of analysed constituents on dry weight basis in UGL and GL legumes, respectively, were as follows: protein, 18.2–23.5 and 19.4–25.7 g, ash, 2.1–2.9 and 2.2–2.9 g, iron, 5.4–7.3 and 7.3–10.3 mg, thiamin, 0.10–0.34 and 0.54–1.83 mg, ascorbic acid, 2.4–3.9 and 3.1–25.6 mg/100 g. The effect of germination and method of cooking on nutrient retention varied, depending on nutrient and severity of heat treatment. Microwave cooking caused 36–57% reduction of ascorbic acid while pressure cooking caused 10–30% loss. The IVSD in raw samples ranged from 18.4% to 22.1% in UGL and 33.6% to 43.6% in GL. Cooking of UGL and GL, by both methods, increased the starch digestibility threefold. The IVPD of raw UGL ranged from 64.6% to 66.2% and that of GL was 72.4–73.9%. In cooked UGL the IVPD ranged from 70.9% to 82.3% and, in GL, from 78.4% to 84.2%, showing a significant difference in cooking methods only in UGL. The iron bioavailability ranged from 11.5% to 18.7% in raw UGL while it was 18.3–20.6% in GL. GL had a higher content of thiamin and ascorbic acid, higher protein and starch digestibility and bioavailable iron, even after cooking.     

Improvement of moistness and texture of high omega-3 fatty acid mackerel nuggets by inclusion of moisture-releasing ingredients

ABSTRACT:  In developing mince-based nugget products using mackerel, an abundant, underutilized, high omega-3 fatty acid species, attention was given to moistness and texture improvement with moisture-releasing ingredients. Three basic approaches were used: added water level variation (0 to 35%), varying added water–moisture-releasing vegetable combination (28/0, 21/7, 14/14, 7/21, 0/28), and varying milk–water combination (0/21, 7/14, 14/7, 21/0). Main ingredients of nugget included mackerel mince, mild cheddar cheese, and hydrated textured soy protein concentrate. The formulated products were molded, lightly battered, flash fried, and frozen until tested. Frozen nuggets were cooked to 65 °C and subjected to the Instron texture analysis (compressive force CF at 70% deformation, expressible fluid EF) and sensory analysis (firmness F, moistness M, overall desirability OD). The 28% added water, 7% moisture-releasing vegetable at 21% water, and 14:7 and 21:0 milk-water combinations were preferred ( P < 0.05). Among the vegetables, onion and mushroom were preferred. Positive correlations were M-OD ( r = 0.82), EF-OD ( r = 0.54), and EF-M ( r = 0.49), and negative correlations were F-OD ( r =−0.83) and CF-OD ( r =−0.34). Milk was more effective than water in rendering moistness and tender texture. The vegetable was effective in forming and making the cooked product moist with less liquid added by holding moisture release during forming and liquid cells after cooking. During warming under the lamps, the least decreases in sensory score, compressive force, and expressible fluid were observed in nuggets made with vegetable and milk.     

Effects of kimchi ethanolic extracts on oxidative stability of refrigerated cooked pork

The antioxidant effect of different kimchi extracts in cooked ground pork during storage for 14 days at 4°C was studied. Cooked ground pork was treated with ascorbic acid, BHT, baechu kimchi (BK), got kimchi (GK), puchu kimchi (PK), and white kimchi (WK) and compared to cooked ground pork without antioxidant. Radical scavenging and chelating activities of kimchi extracts were in the order: GK>PK>BK>WK. Total phenolic contents and flavonoid contents ranged from 32.52 to 46.73 mg of GAE/g and 5.87 to 25.58 mg quercetin/g, respectively. Significantly (P<0.05) lower values of TBARS, peroxide values, and hexanal contents were obtained for GK treated samples compared with cooked pork without antioxidant during refrigerated storage. GK showed good antioxidant activity and was significantly different (P<0.05) from the other treatments. Based on these findings, the natural antioxidants examined may have applications in the development of nutritionally enhanced meat products with enhanced shelf life.