Freshly harvested guava were dipped in 1, 2 and 3% Calcium lactate solution for 5min at room temperature and stored in a chamber at 5% CO2 level where humidity and temperature were 80% and 101C. The stored guavas were analyzed for total phenolic content, antioxidant activity sugars g/100g (glucose, fructose and sucrose) and organic acids mg/100g (citric acid, ascorbic acid, malic acid and tartaric acid). The total phenolic content and antioxidant activity in samples were decreased at termination of storage. The glucose, fructose and sucrose content in control sample were 2.73, 3.30 and 1.66 at the start of storage period which increased to 3.28, 3.66 and 2.08 at the 18th day then after, these declined to 3.22, 3.62 and 2.04 at end of storage, respectively. Citric acid and ascorbic acid content were decreased while malic acid and tartaric acid contents were increased at the termination of storage period. Practical ApplicationsConsumer demand for more natural, minimally processed and fresh foods is increasing. Modified atmosphere storage is a well-proven technology for preserving natural quality of food products in addition to extending the storage life. Modified atmosphere storage is one of the most successful preservation techniques suitable for wide varieties of agricultural and food products. Modified atmosphere storage in combination with pretreatments will help minimize 35-40% postharvest loss of guava fruit which will ultimately benefit guava producers by reducing the wastage of guava fruit.