Effect of Processing Conditions on Calcium Content, Firmness, and Color of Papaya in Syrup

Calcium impregnation is used as a pretreatment in the processing of papaya in syrup. The effect of process temperature (30 and 45°C), calcium source (calcium gluconate and calcium lactate), calcium concentration (0.5 and 1.5% w/w), and pH (4.2 and 6) were studied. The mineral source affected significantly the calcium uptake and the fruit firmness, and therefore, the product quality maximum content of calcium in the fruit was 240 and 72？mg/100？g fresh fruit in 8？h of treatment with calcium lactate and calcium gluconate, respectively. Greater firmness was observed in samples impregnated with calcium lactate. Impregnation treatments did not affect the surface color of fruit. Finally, the effect of cooking in sucrose syrup on product quality attributes (calcium retention, firmness, and color) was analyzed. Cooking in syrup had a positive effect on tissue firmness, despite the decrease of calcium content. During cooking in syrup, calcium content of treated fruit decreased between 9% and 37%. However, the calcium content of fruit in syrup was up to 6 times higher than in fresh fruit. Moreover, the cooking stage had a strong influence on color parameters, leading to a processed product darker than fresh fruit. 1. Introduction Papaya (Carica papaya L.) is a fruit native from Central America, widely grown in the subtropical and tropical regions of South America. This fruit can be an important source of carotenes, vitamin C, and Mg [1, 2]. In Argentina, the papaya is mainly marketed as fresh fruit, fruit in syrup, and jam. The papaya in syrup consumed in South America has singular mechanical characteristics: firm surface and soft inner of fruit tissue. Usually, this effect is achieved through successive stages of osmotic dehydration prior to boiling in sucrose syrup. In this sense, the positive effect of calcium on mechanical properties of different fruits has been widely studied. Calcium is related to vegetable tissue firmness because of its interactions with pectin of cell wall [3, 4]; in general, calcium uptake increases the firmness of plant tissue [5]. Normally, treatment with calcium solutions is applied before other fruit processings. Thus, the effect of the spraying with calcium solutions on texture and sensory attributes of frozen raspberries and blackberries was studied [6]; similarly a positive correlation between calcium content and hardness of baby carrots by effect of soaking in aqueous calcium chloride solutions was reported [7]. Positive results of calcium impregnation in osmotic dehydration have been observed in different fruits such as papayas