Effects of chitosan and nano-SiO2 concentrations on the quality of postharvest guavas (Psidium guajava L.)

Guava (Psidium guajava L.) is a perishable fruit susceptible to postharvest losses at tropical ambient temperature. Therefore, the development of green storage solution such as biodegradable film could be an alternative to increase guavas’ shelf life. The primary objective of the present work was to explore the effects of combining chitosan and nano-SiO2 coating at different concentrations on the external and internal quality parameters of guavas during 12-d storage at 15°C, and 8-d storage at 30°C. Weight loss, skin colour, firmness, ascorbic acid content, total soluble solids (TSS), decay incidence, and sensory taste score during storage were also analysed. Guavas coated with 2% chitosan and 0.02% nano-SiO2 film were economically optimum to maintain the tested postharvest quality parameters, including better skin colour, higher TSS, fruit firmness, ascorbic acid content, and good taste scores, while keeping lower weight loss and decay incidence when compared with those of other treatments at both tested temperatures. Therefore, chitosan and nano-SiO2 as a coating is a promising strategy for improving the postharvest quality of guavas.

Antioxidant-Incorporated Poly(vinyl alcohol) Coating: Preparation, Characterization, and Influence on Ripening of Green Bananas

In this study, the gallic acid (antioxidant)-rich leaf extract of Ficus auriculata was incorporated into poly(vinyl alcohol) (PVA) and utilized as a coating to delay the ripening of green bananas. The films exhibited low opacity of 0.86 ± 0.014 for pure PVA (PP) and 0.92 ± 0.019, 0.99 ± 0.020, and 1.18 ± 0.029 for PVA + 1% extract (PE1), PVA + 5% extract (PE5), and PVA + 10% extract (PE10), respectively, indicating excellent transparency. The weight loss was higher in the uncoated group than in any coated fruits. The reduction in titratable acidity and the increase in total soluble sugars were slower in all of the coated samples as compared to the uncoated ones. The fruits without any treatment attained complete maturity on the ninth day where the ion leakage was 85.61 ± 2.33% while that of PP was 56.36 ± 2.95% and those of PE1, PE5, and PE10 remained below 30%. The coated samples showed better retention and consequently slower degradation of chlorophyll. The fruits coated with pure PVA as well as 10% extract-incorporated PVA remained acceptable till day 15, while the ones with 1 and 5% of extract reached full ripeness on day 18. Results of the present investigation suggest that safe, low-cost, and environmentally friendly coatings can improve the shelf life of perishable produces like bananas.

Banana Waste-to-Energy Valorization by Microbial Fuel Cell Coupled with Anaerobic Digestion

Banana is the most cultivated fruit plant in the world. It is produced in Latin America, Asia and Africa. India and China are the world’s largest banana producers, with almost 41% of the world’s production. This fruit reaches a total world production of 158.3 million tons per year. However, during their production cycle, the banana agroindustry produces large volumes of solid waste derived from overripe fruit. It contributes between 8–20 percent of the waste (around 100 kg of banana waste for every ton of banana produced). Therefore, the use of overripe banana waste represents a huge opportunity for bioenergy production. This work demonstrates that banana waste can be further used for power generation using a microbial fuel cell (MFC) coupled with anaerobic digestion (AD). First, the maximum methane production (MMP), methane production rate (MPR) and biochemical methane potential (BMP) were measured using an anaerobic batch bioreactor for 64 days of monitoring. Finally, the digestate generated from AD was used in the MFC to determine the polarization curve, maximum voltage, maximum power density (MPD), resistance and current. As a result, the AD generated an MMP of 320.3 mL, BMP of 373.3 mLCH4/gVS and MPR of 18.6 mLCH4/Lb⋅day. The MFC generated 286 mV (maximum voltage), 41.3 mW/m2 (MPD), 580.99 Ω (resistance) and 0.0002867 A (current). Both processes together produced a total bioenergy of 13.38 kJ/gVS. This coupled system showed a suitable and promising use of banana waste for ecofriendly bioenergy generation. Therefore, this feedstock could be taken advantage of for generating sustainable processes and developing a circular economy in the banana agroindustry.