Effect of Room Temperarure Storage on the Levels of Carotenoids, Total Phenolic Content and Antioxidant Activity of Lycopersicon Esculentum and Citrullus Lanatus
Noncommunicable diseases (NCDs) such as cardiovascular disease, cancer and chronic respiratory diseases are economically burdening, causing more deaths worldwide than all other causes of death combined. The global burden of these diseases is projected to increase tremendously with an estimated global death of 75 % by 2030. Unhealthy diets, tobacco use, exposure to environmental carcinogens and physical inactivity are documented as the major causes of NCDs. The major contributing factor is due to the production of reactive oxygen and nitrogen species in biochemical reactions in human cells whose presence needs to be counteracted by antioxidants, thus providing a balanced oxidants-antioxidants environment in human system. Moving beyond a focus on treatment toward preventive interventions that minimize environmental and behavioral risk factors of these diseases, dietary approach is deemed not only cheaper, but sustainable. From epidemiological studies, regular consumption of food rich in antioxidants (carotenoids and phenolics) ensures significant reductions of NCDs. Antioxidants are substantially evident to be present in fruits and vegetables such as Lycopersicon esculentum (tomato) and Citrullus lanatus (watermelon). However, other than the challenge of their high perishability, a knowledge gap is presented on the effect of room temperature (RT) storage on the levels of the antioxidants. Three varieties, each of tomato and watermelon grown in Mwea, Kenya were studied for their carotenoid (β-carotene, lutein, lycopene) levels; antioxidant activity (AA) and total phenolic content (TPC) within a 14 day storage period at RT. Carotenoids, TPC and AA were determined using HPLC, FCR and DPPH assay respectively. Results of the carotenoid levels ranged as follows: β-carotene; 0.13±0.03-5.28±0.04 μg/100 g (tomatoes) and 0.13±0.03-3.15±0.02 μg/100 g (watermelons), lutein; 10554.07±177.87-29041.02±156.40 μg/100 g (tomatoes) and 10357.58±62.98-30573.99±434.40 μg/100 g (watermelons), lycopene; 90.34±0.17-515.21±1.77 μg/100 g (tomatoes) and 113.42±0.39-522.76±1.36 μg/100 g (watermelons). The AA ranged between 5.24±0.03-50.77±0.22 and 41.73±0.06-59.24±0.09 % (in fresh and dried tomatoes); 3.10±0.04-41.35±0.29 and 59.12±0.15-79.93±0.18 % (in fresh and dried watermelons), while the TPC ranged between 496.67±67.86-1521.33±143.54 and 348.33±0.58-1023.00±1.00 mg/100 g GAE (in fresh and dried tomatoes); 266.00±5.00-1579.00±59.27 and 335.60±0.58-652.05±19.50 mg/100 g GAE (in fresh and dried watermelons). There were significant differences (P<0.05) of all measurements in all sample varieties. Generally, levels of β-carotene, lycopene, AA and TPC decreased while lutein increased with storage time, indicating the effect of storage on the nutritional values. Findings point towards minimal storage periods of these fruits not only to address perishability but also ascertain intake of higher carotenoid and phenolic levels as well as effective antioxidant activity. The latter two have implications on the fight against NCDs.