Vincenzo Vacca

Changes of flavonoids, vitamin C and antioxidant capacity in minimally processed citrus segments and juices during storage

Abstract Citrus fruits of different species and cultivars, (“Red blush” grapefruit, “Palazzelli” mandarin-type fruit, “Minneola” tangelo and “Salustiana” and “Shamouti” orange) were minimally processed as segments or juices and cold-stored for up to 12 or 15 days, respectively. The flavanone glycosides, ascorbic acid (AA) content and antioxidant capacity were determined during storage. Minimal processing had almost no effect on the main chemical constituents, but ascorbic acid decreased significantly in “Minneola” and “Salustiana” segments, with values ranging from 1.63 to 5.10 mg per gram of dry matter, although only in the last samples taken. One of the three juices (Salustiana) also showed a decrease in AA content. The segments and juices showed different behaviour during storage with regard to the flavonoid content, which ranged from 0.77 mg to 8.32 mg/g dry matter in Palazzelli mandarin and Red blush grapefruit, respectively. A significant increase in total flavonoids (mainly hesperidin) was found in the segments, while the juices showed a diminution in flavonoid content . Antioxidant capacity increased significantly in “Red blush” grapefruit juices and “Salustiana” orange segments, decreased in “Salustiana” juices and “Minneola” tangelo segments and remained constant in the other samples. The antioxidant capacity, moreover, was clearly correlated ( r =0.968 and r =0.889 in segments and juices, respectively) with the ascorbic acid content rather than with the presence of flavanone glycosides.

Preliminary Characterisation of Sardinian Red Grape Cultivars (Vitis vinifera L.) According to Their Phenolic Potential

Fourteen cultivars and clones, mainly selected from the island of Sardinia (Italy) and grown in a collection field, showed significant quantitative differences in phenolic potential. An extraction method designed to reproduce the winemaking process was used to determine the amounts of extractable polyphenols, anthocyanins, catechins and proanthocyanidins reactive to vanillin, and the proanthocyanidins in grape skins and seeds. The Sardinian cultivar Nieddera and the Spanish cultivar Graciano had the highest concentrations of extractable polyphenols, anthocyanins, catechins and proanthocyanidins reactive to vanillin. Four clones of the Cannonau cultivar (synonym Grenache) exhibited fairly high variability, with significant differences in berry and seed phenolic contents.

Changes during storage of quality parameters and in vitro antioxidant activity of extra virgin monovarietal oils obtained with two extraction technologies

Extraction technology has a great effect on quality of olive oils. This paper studied 18 months of storage of two Sardinian extra virgin monovarietal oils obtained with a traditional and with a low oxidative stress technology. Oil samples were subjected to the following chemical analyses: acidity, peroxide value, ultraviolet light absorption K₂₃₂ and K₂₇₀, carotenoids, chlorophylls, tocopherols and total polyphenols. The antioxidant capacity of oils, polyphenol extract and oil extract (remaining after polyphenol extraction) was also determined as radical scavenging activity. The results show that both extraction technologies resulted in minor changes in legal and quality indices during storage, due surely to the high quality of the oils as well as to the very good storage conditions used. Oils obtained with the low oxidative stress technology showed lower peroxide value and acidity and resulted in up to 103% higher total polyphenol content as well as increased radical-scavenging activity, with respect to oils obtained with the traditional technology.

Wine yeasts and resveratrol content

During fermentation in a liquid synthetic medium there was a 30% decrease in resveratrol (a phenolic compound of wine) due to the action of wine yeasts.

5.14 – Minimal Processing of Fruit and Vegetables: Influence on Concentration and Activity of Some Naturally Occurring Antioxidants in Orange Derivatives

Nutritional factors are widely proved to be critical for human health. Overwhelming, evidence from epidemiological studies showed that diets rich in fruit and vegetables are associated with a reduced risk of degenerative diseases. This is attributed to the fact that these foods may provide an optimal mix of phytochemicals, such as antioxidants and their precursors. However, it is widely recognised that the health promoting capacity of fruit and vegetables strictly depends on their technological history. Processing is expected to affect content, activity and bio-availability of naturally occurring antioxidants. Although some experimental evidence has recently demonstrated that processing may have many effects, not always resulting in a loss of the health promoting capacity of fruit and vegetables, uncertainty still exists about the effective incidence of the various technological steps. This aspect, which is generally neglected or scarcely considered in present nutritional and epidemiological studies, is of great importance, considering that only a small amount of fruit and vegetables are consumed as fresh, whilst most of them need to be processed for safety, quality and economic reasons. Thus, investigation on the effects of processing on the activity of naturally occurring antioxidants is a key factor in order to find out the best technological conditions for preserving the above cited beneficial properties and to achieve a correct interpretation of data on dietary habits and human health. In the present investigation fresh and pasteurised orange juices, chosen by virtue of their high content in naturally occurring antioxidants and their widespread consumption, were considered. The changes in ascorbic acid concentration and in the overall antioxidant properties during juice preparation and storage, the latter carried out under different temperature conditions, were studied.

Interaction between film-forming yeasts and phenolic acids

Ninety strains of film-forming yeasts of the Saccharomyces genus were screened for their ability to use phenolic acids. None were able to use phenolic acids as a sole carbon source. When ethanol at 2% was added to the medium, however, the yeasts were able to grow, exhibiting florization accompanied by decolouration.