The objective of the proposed experiment was to determine changes in the content of vitamin C in the vegetable material (fresh and processed) during a certain period of time, and to determine the optimal expiry date of a product (in terms of the vitamin C content), as well as to introduce students to common factors adversely affecting the content of vitamin C in food products (with a special emphasis on oxidizing enzymes). The research revealed that regardless of the type of cucumbers (fresh, pickled in brine or in vinegar), the content of vitamin C is rapidly dropping after the destruction of the cellular structure (grating, slicing etc.). In the case of fresh cucumbers, it is a process determined by two factors: release and activation of ascorbinase from the destroyed cellular structure and availability of oxygen. Low pH values in the remaining cases reduce the effect of ascorbinase, and a decrease in the vitamin C content is related to the process of oxidation with atmospheric oxygen.
Introduction: Advanced glycation end-products (AGE) and advanced oxidation protein products (AOPP) are the main products of glycoxidative modification in diabetes. Objective: The aim of this study was to identify the natural substance with the strongest antiglycoxidative properties among dietary supplements or medicines available without prescription in Poland. Methods: Bovine serum albumin (BSA), vitamin C (VC), aminoguanidine (A), quercetin (Q) and green tea (GT) were tested in vitro in comparison to controls in glycation, oxidation and glycoxidation processes. The decreased AGE and AOPP concentrations were measured as markers of these processes. Results: AGE level was reduced by 72% by VC and at least by 43% by all examined substances in the glycation process. AOPP was reduced by 99% by VC and at least by 40% by all examined substances in the oxidation process. Formation of AGE/AOPP was inhibited by 61% by Q and by 97% by A, and at least 49/88% by all examined substances, respectively. This lowering of AGE/AOPP level was statistically significant (p<0.001) for all test substances in comparison to the positive control C(+). Conclusion: All examined substances are able to inhibit glycative, oxidative and glycoxidative modification of proteins in different degrees depending on their concentration.
Yielding and Fruit Quality of Three Sweet Pepper Cultivars from Organic and Conventional Cultivation
The investigations were undertaken to study the effect of cultivar and growing system (organic vs. conventional) on sweet pepper (Capsicum annum L.) yielding, fruit morphology and antioxidants content.
Two hybrids Caryca and Roberta and one open pollinated cultivar Mercedes all of the Polish origin were compared during 2007 and 2008 in the field experiments. Conventional production was based on mineral fertilization and chemical plant protection, while organic relied on compost fertilization and stabilized ecosystem with no chemical used according to EU Regulation 2092/91 for organic farming. The results revealed a good response of bell pepper to organic cultivation system. Marketable fruit yield was higher and morphological characters better from organic cultivation. The content of human health beneficial compounds such as acsorbic acid, total flavonoids, soluble phenols and beta- carotene were investigated at the red stage of fruit maturity. Both the cultivar and growing method influenced the level of examined compounds. Pepper fruits obtained from organic cultivation system comprised higher amount of vitamin C, beta-carotene total flavonoids and polyphenols than from the conventional. Roberta F1 revealed the higher content of vitamin C, beta-carotene than Caryca F1 and Mercedes. Moreover cultivar Roberta F1 demonstrated the highest level of polyphenols in both cultivation systems.
Growth, Development, Yield and Quality of Middle and Large Fruit Size Greenhouse Tomato - On-Farm Research
Four tomato cultivars from the Seminis Vegetable Seeds Company: large size Red Chief F1 and Ivone F1 fruits and middle size Flexxione F1 and Brillant F1 fruits were used in the experiment. There were six plants on each slab of rockwool. Plant density was 2.5 plants·m-2. Tomato plants were grown according to a system for one main shoot or two shoots in which case fruits for the experiment were collected from the main shoot or from fruit bearing lateral shoots (two plants on each mat). The measurements included a week's increase of the shoot length, the diameter of the stem, the length of the leaf, number of leaves, number of blooming cluster, number of cluster set, number of harvesting cluster and plant loading with fruits.
Fruit firmness as well as the content of dry matter, vitamin C, total sugars, titratable acidity, pH of the cell sap, soluble solids, NO3, P, K, Ca and the content of nutrients such as N, P, K, Ca in the leaf samples which allowed the assessment of the state of plant nutrition, were determinared. Large size fruit tomato cultivars produced higher total commercial yield than middle size fruit cultivars. Middle size fruit cultivars produced higher early yield. The large size fruit cultivars showed better yielding in the autumn than the middle size fruit cultivars. The plant growth depended on the type of the cultivar. The stem diameter of tomato plant depended on the cultivation conditions. A smaller stem diameter was observed with the higher EC in the root environment. In 2006 fruits were characterized by a higher content of vitamin C, total sugars, soluble solids, nitrates, phosphorus and calcium than in the year 2007. Higher values of chemical components (dry matter, vitamin C, titratable acidity, soluble solids, nitrates, phosphorus, potassium and calcium) were obtained in tomato fruits harvested in summer than in autumn time. Large size fruits contained a little more dry matter, total sugars, nitrate ions and phosphorus, but less vitamin C than middle size fruits. On the other hand, middle size tomato fruits were firmer than large size fruits and contained more vitamin C and calcium. No clear differences in fruit quality were observed depending on different systems of plant growing.
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