# Efficacy of Herbal Extracts-Based Nano-Formulations in Extending Guava Fruit Shelf-Life
## 1 Introduction  
The guava (_Psidium guajava_ L.) is a resilient, easily adaptable, and evergreen tree of the _Mytraceae_ family that is grown in tropical and subtropical climatic regions. It is planted for its edible fruit [1]. India ranks first in the production of guava and mangoes (including mangosteens) (45.89%), papayas (44.05%) and bananas (26.08%) as per FAO data in 2020. India's export of fresh fruits has surged in recent years and guava export has shown a record growth of 260% since 2013, rising from 0.58 million in 2013-2014 to 2.09 million in 2021-2022. As per Statista Research Department data, the estimated guava production in India was 4.43 million metric tons (MMT) in 2021 compared to 4.36 MMT in 2020. The total area under guava cultivation was 304 thousand hectares in 2021. The major production areas of the country are state of Maharashtra, Andhra Pradesh, Tamil Nadu, Gujarat, and Karnataka. Guavas are nutrient rich fruit having a high content of vitamin A, vitamin C, antioxidants and minerals and consumed in both processed and fresh form [2]. They are climactic in nature and are highly perishable which leads to high post-harvest losses [3]. Post-harvest loss of horticulture crops in India ranges between 5-39%, as per the Association of Social and Economic Transformation (ASET) reports. For guava, the post-harvest loss stands at 20-40% of the produce. This loss occurs due to improper storage of fruit and lack of packaging amenities. There is high loss in the fruit firmness, physiological weight and change in ascorbate, antioxidants, and total soluble solids (TSS) during fruitstorage [4]. Microbial infestation is also a major reason for post-harvest losses. Guava has high moisture content and is prone to high microbial infestation. The use of antitranspirants [5], wax coatings [6], ethylene inhibitor and irradiation [7] can increase the longevity of harvested fruits. However, the use of chemicals such as antitranspirants and ethylene inhibitors has a negative impact on human health and results into poor consumer acceptability. Wax coatings' main limitation is that they create an anaerobic environment inside fruits by limiting oxygen due to which fermentation takes place. Wax coated fruits appear good but sometimes smell alcoholic due to anaerobic fermentation. Thus, use of coatings (edible films/coatings) which are environment friendly and consumed along with fruit have become popular. Edible films/coatings act as a shield against deteriorating agents and are used for enhancement of fruit shelf life [8]. Edible coatings are used to preserve fruit quality, maintain fruit firmness, and retard microbial damage to fruits and vegetables. They are applied as thin films on the fruit surface, invisible to the naked eye [9]. Lipids, proteins, polysaccharides, and combinations thereof are used to formulate edible coatings [10; 11]. Herbal extracts having great medicinal, antioxidant and antimicrobial activities in combination with biopolymer conjugates are used nowadays for treatment of postharvest fruits to enhance the shelf life of fruits. Ginger extract has been used to enhance the shelf life of plantain [12], papaya [13] and mango [14]. Similarly, garlic extract has been used for mango [15] and banana [16]. In the present study extracts of giloy and ajwain were used through synthesis of nanoformulations with combinations of sodium alginate and CaCl\({}_{2}\). Giloy (_Tinospora corifolia_) has many medicinal properties such as immunomodulator, anti-arthritic, anti-osteoporotic and hepatotoxicity. As per the ayurvedic system, it is used to treat ailments such as urinary diseases, dysppesia, and general debility [17]. The silver nanoparticles synthesized using _Tinospora coridifolia_ stem showed strong antibacterial properties and a zone of inhibition for antibacterial activity of range from 10 \(\pm\) 0.58 to 21 \(\pm\) 0.25 mm was formed [18]. Ajwain (_Trachyspernun amuni_ L.) is an herbaceous plant of the _Apiaceae_ family. It is mostly cultivated in arid and semi-arid soils having high salt concentrations.