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Determination of naringin and hesperidin in citrus fruit by high-performance liquid chromatography. The antioxidant potential of citrus fruit

100%

Gorinstein S. , Huang D. , Leontowicz H. , Leontowicz M. , Yamamoto K. , Soliva-Fortuny R. , Martin-Belloso O. , Martinez-Ayala A. L. , Trakhtenberg S.

Acta Chromatographica

2006

tom No. 17

108-124

Naringin and hesperidin in dimethyl sulfoxide extracts of citrus fruit (oranges, red and blond grapefruit, and sweeties – a hybrid of pummelo and blond grapefruit) have been analyzed by high-performance liquid chromatography with a mobile phase prepared from 2% aqueous acetic acid and acetonitrile. The detection wavelength was at 285 nm. Antioxidant assays based on hydrogen atom-transfer reactions (oxygen radical absorbance capacity, ORAC) and on electron transfer (total phenols by use of Folin–Ciocalteu reagent, FCR; trolox-equivalent antioxidant capacity, TEAC; ferric ion-reducing antioxidant power, FRAP; and reaction with 1,1'-diphenyl- 2-picrylhydrazyl, DPPH) were used to compare the antioxidant potential of citrus fruit and their main flavonoids. The three antioxidant assays (FRAP, TEAC, and DPPH) were performed with prolonged duration of the assay time, because all fruit extracts require long reaction times to approach the end point in the scavenging reaction. Lipophilic and hydrophilic fractions from citrus fruit were investigated by the ORAC reaction. Relationships between the main flavonoids, total polyphenols, and antioxidant potential obtained by use of the FRAP, TEAC, and DPPH procedures showed that correlation coefficients are higher for polyphenols than for the main flavonoids (as markers of 100% citrus juices). HPLC is a precise method for obtaining reliable data on the bioactivity of citrus fruit grown under the same geographical and climatic conditions. The bioactivity of citrus fruit studied by use of five different antioxidant assays was in the order sweetie > red grapefruit > blond grapefruit = orange. Hesperidin and naringin are only partially responsible for the overall antioxidant activity of citrus fruit.

Effects of novel processing techniques on glucosinolates and membrane associated myrosinases in broccoli

100%

Blok Frandsen H. , Ejdrup Markedal K. , Martin-Belloso O. , Sanchez-Vega R. , Soliva-Fortuny R. , Sorensen H. , Sorensen S. , Sorensen J. C.

Polish Journal of Food and Nutrition Sciences

2014

tom 64

nr 1

High pressure/high temperature (HP/HT) and pulsed electric field (PEF) treatment of food are among the novel processing techniques considered as alternatives to conventional thermal food processing. Introduction of new processing techniques with fast and gentle processing steps may reveal new possibilities for preservation of healthy bioactive compounds in processed food. However, effects on various food components due to autolysis and fast reactions prior to the applied HP/HT or PEF need to be considered as the total contribution of processing steps affects the obtained food quality. The present experiments were performed on broccoli (Brassica oleracea var. Italica) florets, purée and juice. Specific focus was given to effects of HP/HT and PEF processing on the content of glucosinolates and activities of myrosinase isoenzymes (EC.3.2.1.147) in the broccoli preparations. Certain conditions applied in HP/HT processing of broccoli florets were able to maintain a high level of intact glucosinolates. Treatment at 700 MPa and 20°C for 10 min was found to inactivate myrosinase activity, but also pressure treatments at 300 MPa and 20°C were able to maintain a high level of intact glucosinolates present in the untreated broccoli florets. PEF processing of broccoli purée and juice showed that the myrosinase activities resulted in nearly total glucosinolate transformations as result of autolysis during puréeing and juice making prior to the PEF processing. These data demonstrated that insight into potential effects on myrosinase activities from application of PEF processing implies specific focus on the sample steps preceding the PEF processing.