Ascorbic Acid and 5-Methyltetrahyclrofolate Losses in Vegetables with Cook/Chill or Cook/Hot-Hold Foodservice Systems

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.

Ethyl cellulose microcapsules for protecting and controlled release of folic acid

Ethyl cellulose microcapsules were developed for use as a drug-delivery device for protecting folic acid from release and degradation in the undesirable environmental conditions of the stomach, whilst allowing its release in the intestinal tract to make it available for absorption. The controlled release folic acid-loaded ethyl cellulose microcapsules were prepared by oil-in-oil emulsion solvent evaporation using a mixed solvent system, consisting of a 9:1 (v/v) ratio of acetone:methanol and light liquid paraffin as the dispersed and continuous phase. Span 80 was used as the surfactant to stabilize the emulsion. Scanning electron microscopy revealed that the microcapsules had a spherical shape. However, the particulate properties and in vitro release profile depended on the concentrations of the ethyl cellulose, Span 80 emulsifier, sucrose (pore inducer), and folic acid. The average diameter of the microcapsules increased from 300 to 448 microm, whilst the folic acid release rate decreased from 52% to 40%, as the ethyl cellulose concentration was increased from 2.5% to 7.5% (w/v). Increasing the Span 80 concentration from 1% to 4% (v/v) decreased the average diameter of microcapsules from 300 to 141 microm and increased the folic acid release rate from 52% to 79%. The addition of 2.5-7.5% (w/v) of sucrose improved the folic acid release from the microcapsules. The entrapment efficiency was improved from 64% to 88% when the initial folic acid concentration was increased from 1 to 3 mg/ml.

Alginate–pectin microcapsules as a potential for folic acid delivery in foods

Most naturally occurring folate derivatives in foods are highly sensitive to temperature, oxygen, light and their stability is affected by processing conditions. Folic acid incorporated microcapsules using alginate and combinations of alginate and pectin polymers were prepared to improve stability. Folic acid stability was evaluated with reference to encapsulation efficiency, gelling and hardening of capsules, capsular retention during drying and storage. Use of alginate in combination with pectin produced more robust capsules and contributed to greater encapsulation efficiency. The capsules lost their spherical shape as a consequence of increased pectin. The high alginate capsules, A100:P0 (100% alginate: 0% pectin) and A80:P20 (80% alginate: 20% pectin) were of regular spherical shape, while those with more pectin, A70:P30 (70% alginate: 30% pectin) and A60:P40 (60% alginate: 40% pectin) formed irregular spheres. The loading efficiency, expressed as a percentage of the actual loading to theoretical loading, varied from 55-89% with the composition of the mixed polymers. After 11 weeks of storage at 4 degrees C, folic acid retention in freeze-dried capsules was 100% (A70:P30 and A60:P40), 80% (A80:P20) and 30% (A100:P0). The blended alginate and pectin polymer matrix increased folic acid encapsulation efficiency and reduced the leakage from the capsules compared to those made with alginate alone and showed higher folic acid retention after freeze drying and storage.

Nutritional quality of organic, conventional, and seasonally grown broccoli using vitamin C as a marker

Organically labeled vegetables are considered by many consumers to be healthier than non-organic or 'conventional' varieties. However, whether the organic-labeled vegetables contain more nutrients is not clear. The purpose of this study is to examine the nutritional quality of broccoli using vitamin C, a fragile and abundant nutrient, in broccoli as a biomarker. The vitamin C content was assayed (2,6-dichlorophenolindophenol method) in broccoli samples obtained from supermarkets that are considered the point of consumer consumption. These samples were obtained during different seasons when the broccoli could be either harvested locally or shipped far distances. The findings indicate that vitamin C could be used as a marker under a controlled laboratory environment with some limitations and, although the vitamin C content of organically and conventionally labeled broccoli was not significantly different, significant seasonal changes have been observed. The fall values for vitamin C were almost twice as high as those for spring for both varieties (P=0.021 for organic and P=0.012 for conventional). The seasonal changes in vitamin C content are larger than the differences between organically labeled and conventionally grown broccoli.

Kinetics of ascorbic acid degradation in un-pasteurized Iranian lemon juice during regular storage conditions

The aim of this research was to determine shelf life stability of un-pasteurized lemon juice filled in clear or dark green glass bottles. Presence of light, time and temperature affect the ascorbic acid retention in citrus juices. Bottles were stored at room temperature (27 +/- 3 degrees C) and in the refrigerator (3 +/- 1 degrees C). Total soluble solids, total titrable acidity and pH value were measured every three weeks and analysis was carried out on ascorbic acid content by means of titration method in the presence of 2,6-dichlorophenol indophenol. The study was carried out for 12 weeks after which slight changes in color, taste and apparent texture in some samples were observed and ascorbic acid content reduced by 50%. Soluble solids content, pH value and total acidity were 5.5 degrees Brix, 2.73 and 5 g/100 mL, respectively which appeared not to be significantly influenced by storage time or conditions. Ascorbic acid content initially at 38.50 mg/100 mL was sharply reduced to about 22 mg/100 mL within the first three weeks of storage. The final ascorbic acid content of all samples was about 15 mg/100 mL. The deteriorative reaction of ascorbic acid in the juice at all conditions followed a first-order kinetic model with activation energy of 137 cal mol(-1).

The effects of ripening stage and processing systems on vitamin C content in sweet peppers (Capsicum annuum L.)

Morrón pepper of 'Fresno de la Vega' (Capsicum annuum L.) is a big sweet variety cultivated in the province of León (northwestern Spain). Changes in vitamin C content of this variety of pepper as a function of ripeness, storage and different preservation systems were studied. The ascorbic acid content increases in peppers as they ripen. For green mature, breaker and red peppers values of 107.3+/-1.84, 129.6+/-3.11 and 154.3+/-7.56 mg/100 g edible portion were found. The vitamin C content for green mature and breaker peppers stored at room temperature (20 degrees C) increased up to 10 days of storage, reaching similar values as those obtained for red peppers direct from the plant. However, stored red ripe peppers showed a significant loss in vitamin C content, around 25%. Refrigeration at 4 degrees C for up to 20 days did not change the ascorbic acid content, except for red peppers, which showed losses around 15%. The ascorbic acid content was altered in response to the preservation procedures assayed. Reductions of 12% and 20-25% during the water blanching and canning process, respectively, were observed. Ascorbic acid retention during freezing was 60%, increasing when the product was previously blanched (87%). Dehydration of peppers resulted in an 88% decrease in ascorbic acid content, whereas freeze-drying did not cause significant losses.

Effect of storage period under variable conditions on the chemical and physical composition and colour of Spanish refrigerated orange juices

The effects of the physicochemical and quality characteristics of various minimally pasteurized refrigerated orange Spanish juices and their changes with storage time and temperature were investigated. Essential oils, acidity, conductivity, diacetyl index, hydroxymethylfurfural, formol index, viscosity and ascorbic acid varied with storage time more significantly at 10 degrees C than at 4 degrees C. Density, colour and pectinmethylesterase did not vary at 4 degrees C. Some of the parameters could be used as indicators of quality loss or spoilage of the juices. The degradation kinetics of the concentration of remaining ascorbic acid against time follows a straight line whose slope indicates the degradation rate. A period of at least 42 days at 4 degrees C and 35 days at 10 degrees C was established as the shelf life of the juices.

Vitamin retention in cook/chill and cook/hot-hold hospital food-services

The vitamins with the greatest losses during hot-holding of food (> 10% after 2 hours) are vitamin C, folate, and vitamin B-6; retinol, thiamin, riboflavin, and niacin appear to be relatively stable. The 66 studies reviewed in this article give inadequate information on the losses of many other vitamins. In cook/chill food-services, substantial losses of sensitive vitamins occur during each of the chilling, storage, and reheating stages. Different reheating methods have similar effects on the amount of vitamin retention. Losses of vitamin C and folate can be greater than 30% when food is reheated after storage for 24 hours at 3 degrees C. Current research indicates that under normal operating conditions, with hot-holding limited to less than 90 minutes, vitamin retention is better in a conventional food-service than in a cook/chill system.