In this study, we assessed the quality of essential oil recovered from fruit drop biomass and assessed its usefulness in preventing postharvest diseases in the tangerine ‘Sai-Namphaung’. Greening was the primary cause of the fruit drop, based on the enduring symptoms and occurrence of the disease in the area. Limonene, together with the presence of β-pinene and linalool, was discovered to be prevalent in essential oils of tangerine fruit peel, particularly that of ‘Sai-Namphaung’. Through isolation of citrus postharvest fungi, we were able to identify four genera which were later DNA sequenced using Internal Transcribed Spacer: ITS and subjected to Basic Local Alignment Search Tool (BLAST), with a high possibility (>98% similarity) of being Penicillium digitatum, Colletotrichum gloeosporioides, Fusarium sarcochrum and Geotrichum candidum. Essential oil from ‘Sai-Namphaung’ and ‘Fremont’ peel biomass positively inhibited green mold rot and citrus anthracnose caused by P. digitatum, C. gloeosporiodes, but were less effective than the commercial citrus oil and Zanthoxylum myriacanthum oil. This is the first evidence of ‘Sai-Namphaung’ postharvest diseases caused by these two fungi and their controls using citrus essential oil.

The Sustainable Development Goals (SDGs) contribute to the improvement of production and consumption systems, hence, assisting in the eradication of hunger and poverty. As a result, there is growing global interest in the direction of economic development to create a zero-waste economy or circular economy. Citrus fruits are a major fruit crop, with annual global production surpassing 100 million tons, while orange and tangerine production alone account for more than half of the overall production. During pre- and postharvest stages of citrus fruit production, it is estimated that more than 20% of fruit biomass is lost, due, primarily, to biotic stresses. This review emphasizes causes of fruit losses by pathogenic caused diseases and proposes a bio-circular perspective in the production of citrus fruits. Due to substantial changes in fruit characteristics and environmental conditions, some of the most economically significant pathogens infect fruits in the field during the growing season and remain dormant or inactive until they resume growth after harvest. Peel biomass is the most significant by-product in citrus fruit production. This biomass is enriched with the value-adding essential oils and polysaccharides. For the complete bio-circular economy, these active ingredients can be utilized as citrus postharvest coating materials based upon their functional properties. The overall outreach of the approach not only reduces the amount of agricultural by-products and develops new applications for the pomology industry, it also promotes bio-circular green economic, which is in line with the SDGs for the citrus fruit industry.

In the current study, eleven sooty mold isolates were collected from different tropical host plants. The isolates were identified under Capnodium, Leptoxyphium and Trichomerium, based on morphology and phylogeny. For the secondary metabolite analysis, the isolates were grown on Potato Dextrose Broth (PDB). The well-grown mycelia were filtered and extracted over methanol (MeOH). The metabolites in the growth medium (or filtrate) were extracted over ethyl acetate (EtOAc). The antifungal activities of each crude extract were tested over Alternaria sp., Colletotrichum sp., Curvularia sp., Fusarium sp. and Pestalotiopsis sp. The metabolites were further tested for their total phenolic, flavonoid and protein content prior to their antioxidant and anti-fungal potential evaluation. The MeOH extracts of sooty molds were enriched with proteins and specifically inhibited Curvularia sp. The total phenolic content and 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) activity was largely recovered from the filtrate corresponding to the inhibition of Alternaria sp.; while the flavonoid and free radical reduction suggested a relative induction of growth of the Fusarium sp., Colletotrichum sp. and Pestalotiopsis sp. Hence, this study reveals the diversity of sooty molds in Thailand by a modern phylogenetic approach. Furthermore, the preliminary screening of the isolates reveals the potential of finding novel compounds and providing insights for the future research on secondary metabolites of bio-trophic fungi and their potential usage on sustainable agriculture.

The effect of elevated CO2 in a controlled atmospheric condition (CA) on the quality attributes of fresh-cut spearmint (Mentha spicata) during refrigerated storage is investigated in the present study. Cut stems of spearmint were exposed to the continuous flow of humidified air enriched with 0 (as a control), 5, 10 and 20% CO2 during storage at 5 °C. Weight loss, leaf colour, total phenols, antioxidant activity, aromatic profile, ascorbic acid, ethanol, ammonia and ethanol-acetaldehyde concentrations were measured before and after storage for 5, 10 and 14 days. Over time, CO2 treatments increased the weight loss, surface colour, L* (from white to black) and b* (from blue to yellow) values, but lowered a* (from green to red). When compared to fresh spearmint, the lowest CO2 concentration was able to maintain the overall colour variations. The 20% CO2 treatment showed significant declines in the total phenolic content, antioxidant potential and low appearance score after 10 days, thus its quality assessment was terminated. Vitamin C levels decreased with time in all the treatments, although the 10% and 20% CO2 treatments had the lowest levels. The toxicity of the cell structures detected by the ammonia content increased and was significantly higher in all CO2 treatments. Storage in the CA with the gas composition at 5% preserved the aromatic profiles similar to those stored in air. In conclusion, increased CO2 did not improve the storability of fresh cut spearmint held at low temperatures, and the 20% gas composition had a significant negative impact on the visual quality.