Environmental Science Archives (2025) Vol. IV Issue 2 DOI: 10.5281/zenodo.17218127 686 www.envsciarch.com Drying Behaviour and Kinetic Modelling of Shweta and Purple Guava (Psidium guajava L.) Leaves under Various Drying Techniques Ishwinder Kaur 1 , Mahesh Kumar 1 , Manav Indra Singh Gill 2 , Valerie Orsat 3 1 Processing and Food Engineering Department, Punjab Agricultural University, Ludhiana, India 2 Horticultural and Forestry Department, Punjab Agricultural University, Ludhiana, India 3 Bioresource Engineering Department, McGill University, Ste-Anne-de-Bellevue, Quebec, Canada *Correspondence for materials should be addressed to MK (email: mahesh@pau.edu) Abstract Guava is a delicious fruit loaded with essential nutrients; in addition, its leaves are equally beneficial. It contains various nutritional and bioactive compounds that offer a range of health benefits and can be used as a complement to medicines. The experiments were carried out and replicated thrice to evaluate the concentration of bioactive compounds in the dried leaves. Guava leaves were dried in shade under ambient conditions as well as using tray (50°C, 60°C and 70°C) and microwave drying (360 W, 540 W and 720 W). To explain the drying process, nineteen available models were evaluated for the best fit. The drying data were best explained by the Page model and Verma model in shade drying; Midilli and Kuck model, as well as the Jena and Das model at 70 0 C tray drying; Midilli and Kuck and Logarithmic model for 360 W microwave drying of Purple guava and Shweta guava, respectively. In both guava varieties, L*, a*, b* values were higher in fresh leaves in comparison to shade, tray and microwave dried leaves. The flavonoid contents for fresh Purple and Shweta guava leaves were 49.81 and 31.71 mg QE/ mg dry weight, respectively in comparison to 208.62 mg QE/mg dry weight & 84.79 mg QE/mg dry weight for Purple and Shweta dried leaves. Keywords: Shweta; Purple Guava; Leaf drying; Drying techniques; Modelling Introduction Guava (Psidium guajava L.) belongs to the Myrtaceae family (Kaneria et al., 2011) and is native to tropical America. Due to its wide range of adaptability to soil and climatic conditions, it is grown commercially in tropical and subtropical regions across the world (Singh, 2005). In India, guava is the fourth most important fruit crop after mango, citrus and banana with 265 thousand hectares of cultivated area and an annual production of 4054 thousand MT (Kumar et al., 2019). In the state of Punjab, guava is the 2nd most important fruit crop grown commercially after citrus (Kocher, 2011). The leaves are also known to have several health benefits, such as curing vomiting, diarrhoea, sore throats and inflamed intestinal problems (Gutierrez, 2008). The leaves when chewed are known to give relief to mouth sores and bleeding gums (Kukreja et al., 2012). Anti-viral, anti-inflammatory, anti- plaque and anti-mutagenic activities of guava leaves are also reported by Naseer et al., (2018). The fresh leaves are perishable. The moisture-induced enzymatic and microbiological activities; poor post-harvest handling, delayed transit, and improper storage are the possible reasons for post- harvest losses (Babu et al., 2018). Hence, to preserve the leaves in dried/ powder form with shelf- stable water activities, an adequate drying process is a necessary pre-requisite. The drying is generally done either under natural or artificial conditions. The goal of the optimal leaf drying process is to achieve the required final moisture content while preserving the same high level of nutrients as fresh leaves. ENVIRONMENTAL SCIENCE ARCHIVES ISSN: 2583-5092 Volume IV Issue 2, 2025 RESEARCH PAPER OPEN ACCESS Received: 2025/08/29 Accepted: 2025/09/25 Published: 2025/09/28