Influence of Torrefaction Temperature and Climatic Chamber Operation Time on Hydrophobic Properties of Agri-Food Biomass Investigated Using the EMC Method

Due to the tendency for excessive moisture adsorption by raw, unprocessed biomass, various methods of biomass valorization are in use, allowing for the improvement of physical–chemical biomass properties, including hydrophobicity. One of the methods is torrefaction, which changes the hydrophilic properties of the biomass to hydrophobic. Therefore, in this study, the influence of the torrefaction temperature and the exposure time to moisture adsorption conditions on the hydrophobic properties of waste biomass from the agri-food industry (lemon peel, mandarin peel, grapefruit peel, and butternut-squash peel) were analyzed. The torrefaction was carried out at the following temperatures: 200, 220, 240, 260, 280, 300, and 320 °C. The hydrophobic properties were determined by using the EMC (Equilibrium Moisture Content) method, conducting an experiment in the climatic chamber at atmospheric pressure, a temperature of 25 °C, and relative humidity of 80%. The total residence time of the material in the climate chamber was 24 h. It was shown that the torrefaction process significantly improves the hydrophobic properties of waste biomass. Concerning dried raw (unprocessed) material, the EMC (24 h) coefficient was 0.202 ± 0.004 for lemon peels, 0.223 ± 0.001 for grapefruit peels, 0.237 ± 0.004 for mandarin peels, and 0.232 ± 0.004 for butternut squash, respectively. After the torrefaction process, the EMC value decreased by 24.14–56.96% in relation to the dried raw material, depending on the type of organic waste. However, no correlation between the improvement of hydrophobic properties and increasing the torrefaction temperature was observed. The lowest values of the EMC coefficient were determined for the temperatures of 260 °C (for lemon peel, EMC = 0.108 ± 0.001; for mandarin peel, EMC = 0.102 ± 0.001), 240 °C (for butternut-squash peel, EMC = 0.176 ± 0.002), and 220 °C (for grapefruit peel, EMC = 0.114 ± 0.008). The experiment also showed a significant logarithmic trend in the dependence of the EMC coefficient on the operating time of the climatic chamber. It suggests that there is a limit of water adsorption by the material and that a further increase of the exposure time does not change this balance.

Uji Efek Antioksidan Formulasi Sediaan Sirup Ekstrak Etanol Kulit Buah Jeruk Bali (Citrus Maxima Merr.) Terhadap Malondialdehid Tikus Putih (Rattus Novergicus) Yang Diinduksi Karbon Tetraklorida

Free radicals are any molecule or atom that is unstable because it has one or more unpaired electrons. Free radicals that are formed in the body will produce new free radicals through a chain reaction which eventually increases in number and attacks the body's cells so that tissue damage will occur, therefore antioxidants are needed from outside to neutralize free radicals, the salute is grapefruit peel (Citrus maxima Merr.) This study aims to determine the antioxidant activity of the ethanol extract syrup of grapefruit peel against levels of Malondialdehyde (MDA) blood plasma of male white rats induced by carbon tetrachloride (CCl4). The stages of this study were the first to make a skin extract syrup. grapefruit peel containing 1% extract (F1), 2% extract (F2), 3% extract (F3), and without grapefruit peel extract (F4) as negative control; Furthermore, testing the stability of the syrup preparations before and after storage was accelerated for 12 cycles, and finally the syrup with the best stability was tested for its lipid peroxidation inhibition activity in vivo with blood plasma MDA levels in rats induced by Carbon Tetrachloride. The results showed the results of the syrup stability test. indicates that F3 has the best stability. As for the in vivo test results, F3 showed a decrease in the MDA level of blood plasma in rats which was significantly different from the negative control. The grapefruit peel significantly decreased the MDA level of the rat blood plasma with a value p<0.05. Keywords : Free radicals, Grapefruit Peel, Antioxidant, Syrup Preparation, Malondialdehyde (MDA)

Antibacterial activity of grapefruit peel extracts and green-synthesized silver nanoparticles

Background and Aim: The gradual loss of efficacy of conventional antibiotics is a global issue. Plant material extracts and green-synthesized nanoparticles are among the most promising options to address this problem. Therefore, the aim of this study was to assess the antibacterial properties of aqueous and hydroalcoholic extracts of grapefruit peels as well as their inclusion in green-synthesized silver nanoparticles (AgNPs). Materials and Methods: Aqueous and hydroalcoholic extracts (80% v/v) were prepared, and the volume and mass yields were determined. The synthesis of AgNPs was done in an eco-friendly manner using AgNO3 as a precursor. The nanoparticles were characterized by ultraviolet–vis spectrometry and photon cross-correlation spectroscopy. The antibacterial activity of the extracts was tested on three Gram-positive bacteria (Staphylococcus aureus ATCC 6538, clinical Enterococcus faecalis, and S. aureus) and two Gram-negative bacteria (two clinical Escherichia coli) using various concentrations of extracts (100, 50, 25, 12, and 5 mg/mL and 5% dimethyl sulfoxide as negative control). Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined using the microdilution method. Modulation of cefazoline and ampicillin on resistant E. coli and S. aureus strains was added to the mixture design response surface methodology with extreme vertices design, with the diameters of inhibition and the fractional inhibitory concentration index as responses and factors, respectively. The antibiotic, the ethanolic extract, and water varied from 0.1 MIC to 0.9 MIC for the first two and from 0 to 0.8 in proportion for the third. Validating the models was done by calculating the absolute average deviation, bias factor, and accuracy factor. Results: The volume yield of the EE and aqueous extract (AE) was 96.2% and 93.8% (v/v), respectively, whereas their mass yields were 7.84% and 9.41% (m/m), respectively. The synthesized AgNPs were very uniform and homogeneous, and their size was dependent on the concentration of AgNO3. The antibacterial activity of the two extracts was dose-dependent, and the largest inhibition diameter was observed for the Gram-positive bacteria (S. aureus ATCC 6538; AE, 12; EE, 16), whereas AgNPs had a greater effect on Gram-negative bacteria. The MICs (mg/mL) of the AEs varied from 3.125 (S. aureus ATCC 6538) to 12.5 (E. coli 1 and E. coli 2), whereas the MICs of the EEs varied from 1.5625 (S. aureus 1, S. aureus ATCC 6538, and E. faecalis) to 6.25 (E. coli 1). There was a significant difference between the MICs of AEs and EEs (p=0.014). The MBCs (mg/mL) of the AEs varied from 12.5 (S. aureus ATCC 6538) to 50 (S. aureus 1), whereas those of the EEs varied from 6.25 (S. aureus 1) to 25 (E. coli 1 and E. faecalis). Ethanolic grapefruit extracts demonstrated an ability to modulate cefazolin on E. coli and S. aureus but were completely indifferent to ampicillin on E. coli. Conclusion: Grapefruit peel extracts and their AgNPs exhibit antibacterial properties that can be exploited for the synthesis of new antimicrobials and their EEs may be efficiently used synergistically with other antibiotics against bacteria with intermediate susceptibility.