Composição química, volátil e de comunidades microbianas em flores de torênia e mini-rosas cultivadas em diferentes sistemas orgânicos

Abstract

Flowers Torenia fournieri F. Lind. (torenia) and Rosa chinensis Jacq. (mini-rose) are consumed fresh all over the world and attract attention due to their delicate appearance and mild flavor. Edible flowers are grown in different organic systems that influence the metabolite profile and microbiota composition. The experimental design of this study was divided into 3 stages with the following objectives: 1) determine the color, metabolites (sugars, organic, phenolic and volatile acids) and microbiota (bacteria/fungi) in torenia flowers grown in an organic system using animal fertilizer and biocompost derived from agri-food waste; 2) determine color, metabolites, microbiota and conduct descriptive sensory analysis of red mini-roses cultivated in the aforementioned organic systems; 3) evaluate the effect of plasma by dielectric barrier discharge (DBD) and light (glow) on color, metabolites, bioaccessibility of phenolics, antioxidant activity, microbiota of mini red roses grown in biocompost. The determination of sugars, organic and phenolic acids was carried out using High Performance Liquid Chromatography, while volatile compounds were determined by Gas Chromatography coupled to a Mass Spectrometer. The microbiota was evaluated by amplicon sequencing (16S rRNA and 18S rRNA). In the sensorial, Flash Profile methodology was used and the color was determined instrumentally. Torenia flowers grown in biocompost showed higher levels (p<0.05) of phenolics (especially delphinidin 3-glucoside) and volatiles (especially 3-ethyl-4methylpentanol, cis and trans-2-hexenal), giving them a more purple color and fresh/fruity aroma. Furthermore, they were characterized by greater abundance of the genera Raoultella, Granulibacter, Providencia and Achromobacter, which are related to greater absorption of nutrients from the soil and environmental defense, when compared to flowers grown in animal fertilizer. Mini-roses grown in biocompost showed higher (p<0.05) luminosity and intensity of the red color, concentration of phenolics including cyanidin 3,5-diglucoside related to the red color, fructose and the volatiles hexyl acetate and cis-3-hexenyl acetate, related to the fruity aroma, when compared to those grown in animal fertilizer. Bacteria such as Stenotrophomonas and fungi such as Eurotiales sp, Pleosporales sp were found in higher (p<0.05) abundance in mini-roses grown in biocompost, which also received higher (p<0.05) scores for fruity aroma and red color. than mini roses grown in animal manure. Therefore, the biocompost fertilizer influenced the composition of metabolites and the microbiota of the flowers. No microorganisms that pose a risk to consumer health were identified in both crops used. Miniroses treated with DBD showed higher (p<0.05) concentrations of some phenolics (gallic acid, hesperidin, cis e trans-resveratrol, quercetin 3-glucoside, pelargonidin 3-glucoside) with higher (p<0.05) antioxidant activity in the DPPH assay and higher (p<0.05) mass fraction of some volatiles (ρ-ment-8-en-1ol, β-pinene, 2-methyl-1-hexadecanol, 6-methyl-3-heptanone and palmitic acid). Flowers treated with glow presented a greater number of phenolics with higher (p<0.05) bioaccessibility and antioxidant activity in the FRAP assay. Proteobacteria, Erwiniaceae and Rosenbergiella were dominant in mini-roses, however, the application of DBD or glow reduced the abundance of bacterial communities. The results characterize edible flowers grown in two organic systems, which can be considered for their production and suggest cold plasma treatment (DBD and glow) as an alternative for maintaining the quality of miniroses.