Biochemical and biological characterization of two Brassicaceae after their commercial expiry date

Highlights

• We extracted phenolics from two Brassicaceae at several days after their expiry date.

• We evaluated polyphenols, antioxidant, antimicrobial and antiproliferative activities.

• Extracts with biological properties were obtained from Brassicaceae after expiry date.

Abstract

Two Brassicaceae (Eruca sativa, Brassica oleracea var. sabauda) were stored in air and under a modified atmosphere for several days after their expiry date and then analyzed. The polyphenol content and composition, as well as the antioxidant activity of the extracts, were assessed, compared to the fresh products. Antimicrobial properties on tester strains (Bacillus cereus, Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa) and in vitro anti-proliferative activity were evaluated. The cabbage extracts exhibited antimicrobial activity mainly on the ninth day after the expiry date and retained significant inhibitory effects against colon carcinoma (CaCo-2) cells. The rocket salad extract exhibited antiproliferative but not antimicrobial activity. Overall, our results indicated that they might represent a good source of natural antioxidants with antimicrobial and anti-proliferative activity, also after their expiry date, suggesting their exploitation for the recovery of important biomolecules used in the food and health industry.

Introduction

The food chain begins with the growing of crops, and continues with the distribution and consumption of food, which entails inevitable waste. Waste includes expired or unsaleable foods, losses from cooking, and excess quantities of scrap food. To avoid, or at least limit the production and accumulation of such waste, one route is to use it as much as possible; this involves the exploitation of new potential uses, for example through the recovery of biologically important molecules from food waste, which might be interesting from different point of view (health, agriculture, food packaging, etc.). Citrus peel was one of the first by-products to be utilized to obtain essential oils, flavonoids, sugar and pectin. The product obtained was applied as a natural sweetener and for flavouring of juices and other foods. In the last decade, several researches studied the recovery of bioactive components from vegetable by-products and/or vegetable waste (Galanakis, 2013, Galanakis and Schieber, 2014, Wijngaard et al., 2009) and a large number of projects have been initiated across scientific disciplines. Emerging technologies are today investigated in research level and in some cases applied in the food industry. Natural substances recovered from agro-industrial wastes as phenolic compounds with healthful properties that could fortify foods or used as nutraceuticals (da Silva and Jorge, 2014, Peschel et al., 2006). Bioactive compounds might also represent a safe alternative compared to the synthetic preservatives generally used in food manufacturing and might play effective roles as antimicrobial agents (Fratianni et al., 2010, Nazzaro et al., 2012). Brassicaceae are among the most important sources of food waste both due to the product size and to all pre-market machining processes required before sale. Brassica are of great interest for their nutraceutical properties as they are rich in antioxidants compounds including polyphenols, which are well regarded for their taste and particularly for their health-promoting effects, such as anticancer or antioxidant properties (Cartea, Francisco, Soengas, & Velasco, 2011). Therefore, the ingestion of health promoting compounds directly or by addition to pharmaceutical products (nutraceutical) or other foods (functional foods) after extraction from vegetables provides safe and effective protection against many common diseases (Avato and Argentieri, 2015, Cartea et al., 2016, Duthie et al., 2000, Pandey and Rizvi, 2009). As knowledge concerning the value of nutrients in human health increases, concurrently to the development of new products containing biologically active compounds. Therefore, the objective of this research was to examine the biochemical characteristics and biological properties of extracts from two widespread Brassicaceae (Eruca sativa, Brassica oleracea var. sabauda) stored at 4 °C in air or under a passive modified atmosphere (MAP) (López-Gálveza et al., 2015, Yang, 2011) until 22 d after their expiry date. The final goal was to recover these vegetable scraps that potentially contain substances with applicative potentiality.