A major citrus postharvest pathogen, Penicillium italicum (P. italicum), causes substantial economic losses in citrus. In this study, a citral nanoemulsion containing polymethoxylated flavonoids (PMFs), the antimicrobial compounds from citrus, was prepared. The antifungal activity and potential antifungal mechanisms of the nanoemulsion against P. italicum were evaluated. The results showed that the growth of P. italicum was effectively inhibited by the nanoemulsion, with a minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of 62.5 and 250 mg L−1, respectively. The nanoemulsion significantly inhibited spore germination and mycelial growth, and it altered the morphology of P. italicum. In addition, the permeability of the cell membrane increased with increasing nanoemulsion concentrations, as evidenced by a rapid rise in extracellular electric conductivity and stronger red fluorescence from mycelia (propidium iodide staining). Compared with the control, the nanoemulsion treatment induced a decrease in total lipid and ergosterol contents in P. italicum cells by 64.61% and 60.58%, respectively, demonstrating that membrane integrity had been disrupted. The results indicated that the PMFs-loaded nanoemulsion exerted antifungal activity against P. italicum by disrupting cell membrane integrity and permeability; such a nanoemulsion may be used as a potential fungicide substitute for preservation in citrus fruits.

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The massive citrus seed waste provides a new approach to the shortage of edible oils in China. In this study, the physicochemical properties, fatty acid composition and antioxidant activity of 12 citrus seed oils from China were determined, aiming to provide a theoretical basis for the development and utilisation of citrus seed oil. Results show most of the citrus seeds had a high oil content (28.3%-41.4%), with 2.6% in Zhi (Poncirus trifoliata). The crude oil extracted from the seeds of Dahongpao (Citrus reticulata) and Tongnanningmeng (Citrus limon) could directly meet the 'National Standard for Food Safety Vegetable Oil' (GB 2716(GB -2018. With total phenolic content (TPC) (62.1-2086.8 lg GAE g À1 DW), total flavonoid content (TFC) (59.6-2275.3 lg RE g À1 ) and total carotenoid content (TCC) (37.4-896.6 lg g À1 ), seed oil of Zhi had the highest content of bioactive substances and the strongest antioxidant capacity. The content of unsaturated fatty acids in citrus seed oil ranged from 72.4% to 82.2%, and the SFA: MUFA: PUFA ratio was closer to the recommended intake ratio of 1:1:1 by the Chinese Nutrition Society than other vegetable oils, which have higher nutritional value. Therefore, citrus seed oil is a potentially valuable oil source for healthy edible oil.

Citrus reticulata Blanco cv. Dahongpao is a traditional Chinese citrus variety. Due to the high investment in storage and transport of Citrus reticulata Blanco cv. Dahongpao and the lack of market demand, the fresh fruit is wasted. The processing of fresh fruit into fruit drinks can solve the problem of storage and transport difficulties and open up new markets. Investigating the effects of different drying processes (hot air, freeze, and spray drying) on fruit powders is a crucial step in identifying a suitable production process. The experiment measured the effects of different drying methods (hot air drying, freeze drying, and spray drying) on the nutrient, bioactive substance, and physical characteristics of fruit powder. This study measured the influence of three different drying methods (hot air, freeze, and spray drying) on the nutritional, bioactive substance, and physical characteristics of fruit powder. The results showed that compared to vacuum freeze-drying at low temperature (−60 °C) and spray-drying at high temperatures (150 °C), hot air drying at 50 °C produced fruit powder with superior nutritional quality, higher levels of active substances, and better physical properties. Hot air drying produced fruit powder that had the highest content of amino acids (11.48 ± 0.08 mg/g DW), vitamin C (112.09 ± 2.86 μg/g DW), total phenols (14.78 ± 0.30 mg/g GAE DW), total flavonoids (6.45 ± 0.11 mg/g RE DW), organic acids, and antioxidant activity capacity. Additionally, this method yielded the highest amounts of zinc (8.88 ± 0.03 mg/Kg DW) and soluble sugars, low water content, high solubility, and brown coloration of the fruit powder and juice. Therefore, hot air drying is one of the best production methods for producing high-quality fruit powder in factory production.