Federica Tinello

Study on the antioxidant and antimicrobial activities of Allium ursinum L. pressurised-liquid extract

Allium ursinum L. is widely used as a spice as well as a traditional medicine. The aim of this work was to evaluate the antioxidant and antimicrobial activities (AMAs) of A. ursinum extract, obtained by pressurised-liquid extraction. Several reliable procedures such as 2,2-diphenyl-1-picrylhydrazyl, 2,2-azinobis-3ethyl benxothiazoline-6-sulphonic acid, ferric-reducing antioxidant power assay and oxygen radical absorbance capacity assays were carried out. Vegetable oil stability was evaluated by using Rancimat test. Moreover, AMA was performed on different microorganisms. On the basis of the results obtained, it is confirmed that the A. ursinum extract could be used as a natural ingredient in food and/or pharmaceutical industries.

Evaluation of antibrowning and antioxidant activities in unripe grapes recovered during bunch thinning

Background and Aims Research into new systems for controlling enzymatic browning in the agro-food industry has been focused on eco-friendly alternatives to conventional thermal treatments and traditional additives, which could impair the sensory, nutritional and health properties. The use of unripe grapes for reducing alcohol concentration and pH of wines has been previously reported; however, no studies have been made of the evaluation of unripe grapes as potential functional ingredients to control enzymatic browning and to enhance antioxidant properties of plant products. Methods and Results Unripe berries were collected in two seasons during bunch thinning of Barbera and Merlot vineyards. Merlot grapes, which had the highest antioxidant activity in the 2,2-diphenyl-1-picrylhydrazyl and ferric reducing ability of plasma assays, were also the most effective in preventing enzyme browning, as confirmed by spectrophotometric assays using commercial mushroom tyrosinase, by zymographic techniques on the isoforms isolated from some plant polyphenol oxidases and by in vivo trials on fresh-cut fruits and vegetables. Conclusions The juice of unripe grapes showed not only antibrowning but also antioxidant and whitening activities. Significance Unripe grapes discarded during bunch thinning of vineyards represent for the agro-food industry a significant source of bioactive compounds that are easy to produce and safe for human health, thus converting these agricultural wastes into value-added products.

Effect of Dipping Pre-treatment with Unripe Grape Juice on Dried “Golden Delicious” Apple Slices

The consumption of apple chips is increasing in the last decades because of the consumer’s preferences towards healthy snacks. However, the enzymatic browning, which is attributed mainly to polyphenol oxidase (PPO, EC 1.10.3.1) activity, negatively affects the sensory, nutritional, and antioxidant properties of dried apples as a consequence of the oxidation of phenolic substrates during post-harvest stages. The antibrowning and antioxidant effects of dipping pre-treatments with unripe grape juice as well as reference formulations including a mixture of 1% w/v ascorbic acid and 1% w/v citric acid, 6% w/v NatureSeal®, and 0.1% w/v sodium metabisulfite were evaluated by spectrophotometric and colorimetric assays on dried “Golden Delicious” apple slices. Based on HPLC analysis, the treated apple slices were enriched with bioactive compounds which effectively improved antioxidant capacity and limited enzymatic browning by increasing lightness, reducing color change, and inhibiting PPO activity. Hence, the juice of unripe grapes recovered as agricultural wastes during bunch thinning of vineyards could be proposed as a safe, inexpensive, and eco-friendly alternative to conventional antibrowning treatments in apple processing.

Comparison of OXITEST and RANCIMAT methods to evaluate the oxidative stability in frying oils

The oxidation of fatty acids in the presence of atmospheric oxygen is recognized as one of the main factors affecting the shelf life of oils and fats causing rancidity by the formation of off-flavors due to aliphatic aldehydes or other volatile compounds. Therefore, the oxidative stability is one of the most important parameters to be evaluated in the formulation of commercial frying oils. In this regard, the induction period of 15 frying oils has been measured using two different methods of accelerated oxidation, OXITEST and RANCIMAT, and correlated to their fatty acid content previously detected by gas chromatographic technique. Frying oils containing high contents of saturated fatty acids mainly from the palm oil achieved an improved oxidative stability by increasing their induction period. Moreover, the linear regression analysis showed a good correlation between the induction period values of the two instruments. Hence, the innovative OXITEST method may be an easy, fast, and eco-friendly alternative to the official RANCIMAT method for evaluating the oxidative stability in oil- and fat-containing products.

The Use of Polyphenol Oxidase Activity to Identify a Potential Raisin Variety

ABSTRACT The biochemical characterization of polyphenol oxidase (PPO) in the white grape Bianchetta Trevigiana is addressed in this research to fulfil the requirement for raisin varieties with high concentrations of phenolic compounds and low PPO activity not only to avoid enzymatic browning but also for maintaining the nutritional value of raisins. Spectrophotometric assays and electrophoresis were used to study this ancient variety exhibiting low PPO activity (only cathecolase activity) which reached at the low pH value of grape berry and was about 15% of the maximum enzymatic activity measured. In addition, the visualization of the active isoforms of grape PPO after 2-DE separation of proteins was a key step for further studies using MALDI-TOF-MS and bioinformatic tools. Based on the thermal inactivation profiles, heating treatment at 70°C may be considered a way to inhibit Bianchetta Trevigiana PPO activity by preserving also its high phenolic content. Therefore PPO characterization may be proposed as a marker for identifying potential high value raisin varieties.