Role of acemannan and pectic polysaccharides in saline-water stress tolerance of Aloe vera (Aloe barbadensis Miller) plant.

This study investigates the impact of water and salinity stress on Aloe vera, focusing on the role of Aloe vera polysaccharides in mitigating these stresses. Pectins and acemannan were the most affected polymers. Low soil moisture and high salinity (NaCl 80 mM) increased pectic substances, altering rhamnogalacturonan type I in Aloe vera gel. Aloe vera pectins maintained a consistent 60 % methyl-esterification regardless of conditions. Interestingly, acemannan content rose with salinity, particularly under low moisture, accompanied by 90 to 150 % acetylation increase. These changes improved the functionality of Aloe vera polysaccharides: pectins increased cell wall reinforcement and interactions, while highly acetylated acemannan retained water for sustained plant functions. This study highlights the crucial role of Aloe vera polysaccharides in enhancing plant resilience to water and salinity stress, leading to improved functional properties.

High-Intensity Ultrasound Processing Enhances the Bioactive Compounds, Antioxidant Capacity and Microbiological Quality of Melon (Cucumis melo) Juice.

The bioactive compounds, antioxidant capacity and microbiological quality of melon juice processed by high-intensity ultrasound (HIUS) were studied. Melon juice was processed at two ultrasound intensities (27 and 52 W/cm2) for two different processing times (10 and 30 min) using two duty cycles (30 and 75%). Unprocessed juice was taken as a control. Total carotenoids and total phenolic compounds (TPC) were the bioactive compounds analyzed while the antioxidant capacity was determined by DPPH, ABTS and FRAP assays. The microbiological quality was tested by counting the aerobic and coliforms count as well as molds and yeasts. Total carotenoids increased by up to 42% while TPC decreased by 33% as a consequence of HIUS processing regarding control juice (carotenoids: 23 µg/g, TPC: 1.1 mg GAE/g), gallic acid and syringic acid being the only phenolic compounds identified. The antioxidant capacity of melon juice was enhanced by HIUS, achieving values of 45% and 20% of DPPH and ABTS inhibition, respectively, while >120 mg TE/100 g was determined by FRAP assay. Further, the microbial load of melon juice was significantly reduced by HIUS processing, coliforms and molds being the most sensitive. Thus, the HIUS could be an excellent alternative supportive the deep-processing of melon products.

Mathematical Modelling of Ultrasound-Assisted Extraction Kinetics of Bioactive Compounds from Artichoke By-Products.

Valorization of an artichoke by-product, rich in bioactive compounds, by ultrasound-assisted extraction, is proposed. The extraction yield curves of total phenolic content (TPC) and chlorogenic acid content (CAC) in 20% ethanol (v/v) with agitation (100 rpm) and ultrasound (200 and 335 W/L) were determined at 25, 40, and 60 °C. A mathematical model considering simultaneous diffusion and convection is proposed to simulate the extraction curves and to quantify both temperature and ultrasound power density effects in terms of the model parameters variation. The effective diffusion coefficient exhibited temperature dependence (72% increase for TPC from 25 °C to 60 °C), whereas the external mass transfer coefficient and the equilibrium extraction yield depended on both temperature (72% and 90% increases for TPC from 25 to 60 °C) and ultrasound power density (26 and 51% increases for TPC from 0 (agitation) to 335 W/L). The model allowed the accurate curves simulation, the average mean relative error being 5.3 ± 2.6%. Thus, the need of considering two resistances in series to satisfactorily simulate the extraction yield curves could be related to the diffusion of the bioactive compound from inside the vegetable cells toward the intercellular volume and from there, to the liquid phase.

Effects of acoustic power and pH on pectin-enriched extracts obtained from citrus by-products. Modelling of the extraction process.

BACKGROUND: The ultrasound-assisted extraction of pectic polysaccharides from orange by-products was investigated. Kinetics of mechanical agitation (0.2 × g) and acoustic (US1: 542 W L-1 and US2: 794 W L-1 ) extractions, were obtained and modelled at different pH values (1.5 and 2.0). All extractions were carried out at 25 °C, using citric acid as the extraction solvent. RESULTS: Higher pectic polysaccharides extraction yields were obtained with ultrasonic assistance, in comparison with the results obtained using mechanical agitation. Moreover, yield increases were significantly higher using the more acidic pH. Thus, at pH 1.5, pectin yield increased from ∼19%, obtained with agitation, to ∼47%, applying ultrasound; whereas, at pH 2.0, this increase was from ∼10%, with agitation, to ∼18%, applying ultrasound. A considerable decrease of the galacturonic acid proportion was observed on the extracts when ultrasound were applied for 60 min under pH 2.0. High methoxyl pectins were extracted at pH 1.5 whereas at pH 2.0, pectins exhibited a low methylation degree. Curves of acoustic and mechanical agitation extractions were properly represented by a second-order rate model (average mean relative error ≤ 7.4%). The extraction rate constant, initial extraction rate and maximum yield were determined for all experimental conditions. CONCLUSION: Overall, the results clearly indicated that the effect of ultrasound was highly dependent on the pH. Therefore, adequate acidic conditions must be applied in order to improve the efficiency of ultrasound on the pectin extraction process. © 2019 Society of Chemical Industry.