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Freeze-drying and heat-drying (60–120 °C) experiments were performed with avocado peels, and changes in the phenolic profile of the peels were examined in relation to various activities, including antioxidant (ABTS and DPPH) activity; antibacterial activity against S. aureus, E. coliand P. aeruginosa; and inhibitory activity against α-glucosidase. Twenty-nine metabolites were identified as caffeoylquinic acid derivatives, procyanidins types A and B, and flavonoids. Freeze-drying preserved the highest levels of caffeoylquinic acid derivatives, procyanidins, total phenolic (TP) and total flavonoid (TF) contents; antioxidant and antibacterial activities; and inhibitory activity against α-glucosidase. Drying at 120 and 80 °C resulted in similar TP and TF contents, antioxidant activities and inhibitory activities against E. coliand P. aeruginosa, but these parameters were greater to those exhibited by samples dried at 100 and 60 °C. Nevertheless, more caffeoylquinic acid derivatives, procyanidins, and flavonoids were extracted from the samples dried at 120 °C, and a better inhibitory activity for S. aureusand α-glucosidase were obtained; the inhibition of S. aureuswas comparable to that observed for freeze-dried peels. Therefore, compared to the other temperatures, drying at 120 °C was more effective in preserving the phenolic compounds and biological activities of avocado peels.

The quarantine hot water treatment (HWT) reduces the chilling injury (CI) symptoms in mango fruit. In ‘Keitt’ mango this effect is associated with up-regulation of the secondary metabolism in the peel, specifically higher accumulation of gallic acid derivatives, but the metabolic changes of the pulp are unknown. This study analyzed metabolic and expression changes in the pulp of ‘Keitt’ mango to further elucidate the mechanisms associated with the HWT-induced CI tolerance. Mangoes with HWT (46.1 °C, 90 min) and control were stored under CI conditions (20 days at 5 °C) and then ripened (7 days at 21 °C). Methanol extracts were analyzed for total phenolics (TP), antioxidant capacity (ABTS, DPPH, FRAP) and phenolic profiles by UPLC-DAD-MS; the expression of genes encoding phenylalanine ammonium lyase (PAL), chalcone synthase (CHS) and glucosyltransferase (UGT) was analyzed by RT-qPCR. HWT alleviated CI symptoms and protected the membrane integrity as evidenced by lower CI index, electrolyte leakage, and malondialdehyde content values. The metabolites identified (20) were classified as gallotannins, gallic acid derivatives, benzoic acid derivatives, phaseic acid derivatives, and flavonoids. After cold storage and ripening, HWT fruit had higher levels of gallotannins, the most abundant compounds, and other metabolites such as p-hydroxybenzoic acid hexoside and dihydrophaseic acid hexoside. HWT fruit also had higher expression of the UGT gene and higher values of TP and antioxidant capacity (ABTS, DPPH, and FRAP). Thus, the HWT-induced CI tolerance in mango fruit is associated with an enhanced antioxidant capacity in the pulp due to the increased synthesis of gallotannins.

The variability in grain and starch characteristics and their relationship with the accumulation of starch granule associated proteins were investigated in five maize landraces of Northwest Mexico (Blando de Sonora, Chapalote, Elotero de Sinaloa, Reventador, and Tabloncillo). Significant differences were observed in grain hardness related traits, starch physicochemical properties, and structural properties. Blando de Sonora showed very soft grains, whereas the hardest grains were observed for Chapalote and Reventador. Starch granules isolated from landraces with hard grains contained more amylose and showed polygonal shapes, lower crystallinity and enthalpy of gelatinization, and greater retrogradation and proportion of long amylopectin chains. Proteomic analysis identified the enzymes granule-bound starch synthase I (GBSSI), starch synthase I and IIa, starch branching enzyme IIb, sucrose synthase 1, and pyruvate phosphate dikinase 2 as granule-associated proteins. The abundance of GBSSI correlated significantly with amylose content, consistent with the positive correlation observed between amylose and grain hardness. These results showed that the variability in the characteristics evaluated was mainly related to changes in the proportion of amylose in the starch granules, which were associated with differences in the expression of GBSSI. This information may be useful to define strategies for the exploitation and conservation of the landraces.