Ultrasound-assisted extraction and characterization of the functional properties of starch from soursop fruits (Annona muricata L.)

Starch is one of the most used polysaccharides in the food industry because is an excellent raw material to modify the texture and consistency of food. Also, is the main source for energy storage in horticultural products. The starch from soursop fruits can be used as an alternative source with functional properties and a wide field of application in the food industry. The use of emerging technologies such as ultrasound-assisted extraction has improved sensory attributes and functional properties. To the best of our knowledge, extraction of starch by ultrasound from soursop fruits has not to date been documented. Therefore, the objective of this study was to characterize the functional properties of soursop fruit starches by ultrasound-assisted method and determine the presence of acetogenins. Three times (10, 15 and 20 minutes) and three ultrasonic amplitudes (UA) of 20, 30 and 40% for the ultrasound-assisted extraction were used. Total yield, gelatinization temperature, water absorption and solubility index, swelling index, amylose and amylopectin content, presence of acetogenins and starch granule morphology were recorded. The highest extraction yield (ultrasound) was reached using 10 min and 40% UA (6.34%). For the gelatinization temperature, 10 min and 30% UA (82.33 degrees C) were the best conditions. Water Solubility Index (WSI) values of 6.13 +/- 0.00% using 10 min and 20% UA were recorded. Water Absorption Index (WAI) as well as Swelling index (SI) values of 3.34 +/- 0.12% and 3.26 +/- 0.00% were obtained by conventional extraction, respectively. Starch granules morphology showed different size with circular shapes and truncated geometries. Finally, positive qualitative results for the presence of acetogenins by all the extraction methods were obtained.