Postharvest Storage Differentially Modulates the Enzymatic and Non-Enzymatic Antioxidant System of the Exocarp and Mesocarp of Hass Avocado: Implications for Disorders.

The present study evaluated the performance of some enzymatic and non-enzymatic antioxidant systems against oxidative stress for 10 to 30 d of refrigeration (R) and 15 to 50 d in controlled atmosphere (CA) conditions in both exocarp and mesocarp of Hass avocados from early and late harvests and at shelf life (SL) or consumption maturity. The possible relationship of the antioxidant systems with the occurrence of physiological disorders is also evaluated. The results indicate that the enzymatic system-superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), phenylalanine ammonium lyase (PAL) and polyphenoloxidase (PPO)-as well as the non-enzymatic system-such as phenolic compounds (PC)-showed different responses to the stress generated during storage and shelf life. In general, SOD, CAT, PAL and PPO did not significantly vary in storage (R or CA). At consumption maturity, SOD, POD and PAL activities decreased in the mesocarp (RSL and CASL), while CAT increased in the exocarp for CASL15-50d. PC instead decreased in the exocarp as the harvest period progressed while it increased in the mesocarp. Physiological disorders (dark spots) showed only in refrigeration on the exocarp at R30d and in mesocarp at RSL30d coincident with low SOD and low SOD and POD activity values, as well as low PC contents (p-coumaric and its derivatives and caffeic acid derivatives), respectively. The results support the use of CA as a postharvest technology to prevent the development of physiological disorders through the joint action of antioxidative defenses during avocado transport to distant markets until consumption maturity is reached.

In vitro and in vivo biotransformation of glucosinolates from mashua (Tropaeolum tuberosum) by lactic acid bacteria.

Mashua (Tropaeolum tuberosum) is an Andean tuber with a high content of glucosinolates (GLSs). GLSs subjected to biotransformation by plant enzymes or enzymes of the gastrointestinal microbiota give rise to biologically active compounds, to which chemo preventive properties are attributed. In this work, the biotransformation of mashua GLSs was evaluated in vitro by six strains of lactic acid bacteria (LAB) and in vivo using rats with and without previous LAB dosing. The results showed that L. rhamnosus GG utilized the totality of glucosinalbin and glucotropaeolin, and 46.7 % of glucoaubrietin. Four GLSs derivatives were detected. The GLSs were absorbed and metabolized by the rats with low contents in feces (0.02 %) and urine (0.59 %) and were detected up to 3 h after consumption in plasma. The results showed that probiotic bacteria play an important role in transforming GLSs into beneficial compounds for the health of consumers.

Proteomic analysis of mashua (Tropaeolum tuberosum) tubers subjected to postharvest treatments.

Mashua (Tropaeolum tuberosum) is an important food in certain areas of the Andean region, where it is popularly believed to possess medicinal properties. Several studies have previously shown the potential of this tuber as a source of bioactive compounds. Traditionally, the tuber is exposed to the sun before consumption, in order to reduce its bitterness. The present work aims to study, at the proteome level, the differential abundance of proteins in tubers subjected to different postharvest treatments: sun-exposure (SUN), shade (SHA), refrigeration (COLD) and shade combined with sun-exposure (SHA-SUN) compared to recently harvested tubers (INIT). Results showed that sun exposure for prolonged times (9 days) resulted in increased abundance of proteins classified as heat shock proteins, intracellular traffic, disease/defense and protein degradation. Our results reflect that the sun treatment activates defense systems and osmoprotection adjustment against water loss and reactive oxygen species.

Potential of tara (Caesalpinia spinosa) gallotannins and hydrolysates as natural antibacterial compounds.

Gallotannins obtained from tara pod extracts (EE) and from the products of acid hydrolysis for 4 and 9h (HE-4 and HE-9) were characterised for their composition, antioxidant activity, antimicrobial activity (AA) and minimum inhibitory concentration (MIC). Results of AA and MIC showed that EE exerted the highest inhibitory activity against Staphylococcus aureus, followed by Pseudomonas fluorescens; and among these bacteria, the antibacterial potency was enhanced after EE hydrolysis only against S. aureus. The lowest minimum inhibitory concentration (MIC) value (0.13mg gallic acid equivalent (GAE)/ml) was exerted by HE-4 against S. aureus. These results indicate that tara gallotannins have the potential to inhibit pathogenic bacteria with potential application in foods as antimicrobials and their AA can be enhanced by acid hydrolysis.

Prebiotic effects of yacon (Smallanthus sonchifolius Poepp. & Endl), a source of fructooligosaccharides and phenolic compounds with antioxidant activity.

Thirty-five different yacon (Smallanthus sonchifolius Poepp. & Endl) accessions were evaluated as potential alternative sources of fructooligosaccharides (FOS) and phenolic type natural antioxidants. FOS, total phenolics (TPC) and antioxidant capacity (AC) contents in the ranges of 6.4-65g/100g of dry mater (DM), 7.9-30.8mg chlorogenic acid (CAE)/g of DM and 23-136µmol trolox equivalente (TE)/g DM were found. Accession AJC 5189 sparked attention for its high FOS content while DPA 07011 for its high TPC and AC. In addition, the prebiotic effect of yacon FOS was tested in vivo with a guinea pig model. A diet rich in yacon FOS promoted the growth of bifidobacteria and lactobacilli, resulting in high levels of short chain fatty acids (SCFAs) in the cecal material and enhancement of cell density and crypt formation in caecum tissue, being indicative of colon health benefits. This study allowed identification of yacon cultivars rich in FOS, AC and/or FOS and AC for nutraceutical applications.