Characterization of edible films of Swartzia burchelli phosphated starches and development of coatings for post-harvest application to cherry tomatoes

Abstract

The market demand for corn starch and cassava continues to increase because of their use in edible applications, their biodegradable nature, and other appealing properties. As a result, there is a need to identify alternative starch sources, for example, the seeds of S. burchelli, with the potential to be modified for use in post-harvest applications. Therefore, this study aimed to develop and characterize edible films based on the starch phosphates of the seeds of S. burchelli, with the specific aim to apply these starches to cherry tomatoes for post-harvest conservation. After extraction, the starch was phosphorylated with sodium tripolyphosphate (STP) in different concentrations and times according to a 2 x 2 factorial design with additional treatment (native starch). After modification, the starch phosphates were selected for the preparation of edible films using glycerol as a plasticizer, in proportions of 5, 10, 15 and 20% for each selected starch. The films were measured for thickness, permeability to water vapor and solubility in water. According to their permeability values, 4 films were selected for application in the coverage of cherry tomatoes. The conservation of cherry tomatoes with and without coverage was studied over 8 evaluation times (up to 21 days) at 10±2 °C and 80±5% relative humidity. The weight loss, soluble solids, titratable acidity, maturation index, and firmness were measured every 3 days during storage. The starch phosphates showed a phosphorus content within that established by standards, such that the resulting films are acceptable for use in food for human consumption. The edible films presented with an acceptable appearance and without the development of cracks. The concentration of glycerol and the type of starch influenced the characteristics of the films, increasing the permeability and reducing the water solubility of the various edible films. The best result obtained regarding the conservation of cherry tomatoes was observed for fruits with edible coatings of greater permeability to water vapor; such fruits exhibited only a slight decline in firmness during storage compared with the control. It can be concluded that the modification performed on the starch and the glycerol concentration positively influenced the properties of the edible films, allowing for optimal use in post-harvest applications. Similarly, the edible coatings conferred better appearance to the fruits, maintaining their maturation index and firmness during the experimental period and providing better post-harvest storage conditions for the cherry tomatoes.