Chemical Constituents and Antioxidant Potential of Red Guava (Psidium cattleianum Sabine) from Southern Brazil in Different Edible Ripening Stages.

Ripening and growing location are important factors that can impact fruit quality characteristics. In this study, the influence of these factors on physicochemical characteristics, carbohydrates, aliphatic organic acids, phenolic compounds, and antioxidant capacity of red guava (Psidium cattleianum Sabine) was evaluated. Fruit ripening increased fructose and glucose (up to 22.83 and 16.42 g 100 g- 1 dry matter (DM), respectively), and decreased citric acid, the major organic acid (up to 135.35 mg g- 1 DM). Ripening and growing location also influenced the concentration of phenolic compounds and antioxidant capacity of red guava, in which a dependency between both factors was observed in most cases. Apigenin, galangin, isoquercitrin, among other phenolic compounds were quantified for the first time in red guava, in which isoquercitrin was the major (up to 13409.81 mg kg- 1 DM). The antioxidant potential of red guava was also confirmed by ferric reducing antioxidant power assay (up to 82.63 µmol Fe+ 2 g- 1 DM), Folin-Ciocalteu reducing capacity assay (up to 17.79 mg gallic acid equivalent g- 1 DM), and DPPH free radical scavenging assay (up to 25.36 mg ascorbic acid equivalent g- 1 DM). These results especially demonstrated the bioactive potential of red guava and provided knowledge regarding the influence of ripening and growing location on chemical and bioactive components encouraging its industrial exploitation.

High acidity of bracatinga honeydew honey: A new regulatory limit proposal.

The free acidity of bracatinga honeydew honey (BHH) was monthly monitored over short-term storage (four months) until all the samples exceeded 50 mEq kg-1 - the maximum value allowed by the international regulatory honey standards. In addition, BHH quality was also investigated through moisture content, water activity, electrical conductivity, pH, 5-hydroxymethylfurfural, and aliphatic organic acids (AOA) analyses. According to our results, most of the parameters investigated presented significant differences during the short storage period studied; however, the quality parameters (except acidity) did not exceed the limits established by the international regulatory honey standards. Therefore, the high free acidity observed in the BHH samples did not affect its quality. Moreover, the total AOA concentration decreased as the free acidity increased, indicating that the high acidity is not related to postharvest fermentation. Since all BHH samples exceeded the established limit of 50 mEq kg-1 after four months of storage (up to 62.7 mEq kg-1), this data corroborates that this type of honey does not comply with the regulatory honey standards, which represents an obstacle to its commercialization. Therefore, our data reinforce the need for a future reassessment of the international regulatory honey standards regarding the free acidity limit for BHH. In this sense, taking together all the studies developed by our research group since 2014, a new free acidity value of 65 mEq kg-1 is proposed, which may discourage fraud practices and negative impacts on the BHH beekeeping chain.

Brazilian stingless bee honey: A pioneer study on the in vitro bioaccessibility of phenolic compounds.

In this study, the effect of in vitro gastrointestinal digestion of phenolic compounds, the total phenolic content, and the antioxidant potential of stingless bee honey were investigated. Among the 33 phenolic compounds investigated, 25 were quantified, and only eight were not bioaccessible (p-aminobenzoic acid, sinapic acid, pinobanksin, isorhamnetin, quercetin-3-glucoside, syringaldehyde, coumarin, and coniferaldehyde). Benzoic acid was predominant in most undigested samples (21.3 to 2414 µg 100 g-1), but its bioaccessibility varied widely (2.5 to 534%). Rutin, a glycosylated flavonoid, was quantified in all samples and might have been deglycosylated during digestion, increasing the bioaccessibility of quercetin in a few samples. Overall, the concentration of phenolic compounds prior digestion and their bioaccessibility varied greatly among samples. Nevertheless, higher concentrations before digestion were not correlated to greater bioaccessibility. This study is the first to assess the in vitro bioaccessibility of phenolic compounds in SBH, providing novel insights into SBH research.