Daniela Ghirardello

Phenolic Content, Antioxidant Potential, and Antimicrobial Activities of Fruit and Vegetable By-Product Extracts

The use of fruit and vegetable by-products as natural food additives has recently been suggested, due to their richness in polyphenols. The aim of this research study was to determine polyphenolic content and the antioxidative and antimicrobial activities of 13 fruit and vegetable by-product extracts obtained with three solvent mixtures. The Folin-Ciocalteu method was employed to calculate the total phenolic content, while antioxidant capacity was assessed with DPPH· and ABTS ·+. The highest total phenolic content and antioxidant capacity values were obtained for the acetonic extracts. Pomegranate peels and hazelnut skins showed the highest values of total phenolic content (212.3 and 166.3 mg GAE/g dw, respectively) and antioxidant capacity (95.7 and 92.9 of inhibition percentage, respectively, for DPPH· assay). The antimicrobial activity against twelve foodborne pathogens and spoilage microorganisms was evaluated. Pomegranate and apple peels showed the highest inhibition of Staphylococcus aureus and Pseudomonas fluorescens. The results obtained demonstrated that by-products could be used as natural food additives with beneficial health properties.

Chemical, mechanical and sensory monitoring of hot air- and infrared-roasted hazelnuts (Corylus avellana L.) during nine months of storage

Roasted hazelnuts can be consumed as whole nuts, or as an ingredient in the confectionary and bakery industries and are highly appreciated for their typical taste, aroma and crunchy texture. In this work, two hazelnut types (TGT, Ordu) from two harvests were roasted using two different systems (hot air, infrared) at different time/temperature combinations, and the evolution of oxidative stability, the total phenolic content (TPC), the antioxidant capacity, the mechanical and acoustic properties and the sensory perception were determined during storage. The results showed that the oxidative stability was increased by roasting hazelnuts at 120°C for 40min with hot air system. Similar overall trends were not found for the TPC, the antioxidant capacity and the mechanical-acoustic properties. However, for the maintenance of high antioxidant activity, a storage time of 6months at 4°C is recommended. The two roasting systems gave hazelnuts with significant sensory differences only at high roasting temperature.

OPTIMISATION OF ULTRASOUND AND MICROWAVE-ASSISTED EXTRACTION OF CAFFEOYLQUINIC ACIDS AND CAFFEINE FROM COFFEE SILVERSKIN USING RESPONSE SURFACE METHODOLOGY

Ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) of caffeoylquinic acids and caffeine from coffee silverskin (CS) at two particle size were investigated using response surface methodology and compared to a conventional solvent extraction (CSE). The impact of time and temperature on the extraction process was evaluated and extraction efficiency was optimised by measuring total phenolic content (TPC), radical scavenging capacity (RSC), caffeoylquinic acids (TotCQAs) and caffeine content. UAE allowed to obtain extracts with values of TPC, RSC and TotCQAs higher or similar to CSE; moreover UAE produced the highest caffeine content (14.24 g kg-1 dw) with a significant reduction of extraction time.