Study of Instant Controlled Pressure Drop DIC Treatment in Manufacturing Snack and Expanded Granule Powder of Apple and Onion

Abstract

While the use of “puffing” process is mainly limited to products like cereals or carrot, the instant controlled pressure drop (DIC) can treat and expand the large domain of heat sensitive food products. In the present article, this operation is applied on partially dried apple and onion, to produce snack or, by shadow grinding, expanded granule powder. DIC is a high-steam pressure treatment (up to 0.6 MPa in this article), where steam is applied constantly during a short treatment time t (5–55 s) and instantaneously dropping the pressure toward vacuum 5 kPa with a rate higher than 0.5 MPa s−1. The expanded structure allows the product to achieve better functional properties linked with a greater specific surface area. Thus, the time of final hot air drying (with air flow at 40°C, 1 m s−1, and 267 Pa partially pressure humidity) is reduced by about 55% through greater effective diffusivity and initial starting accessibility. The product's nutritional value is partially preserved (vitamins) or even improved through more available flavonoids. DIC can perfectly decontaminate the products, and end quality attributes are higher than normally dried or as good as freeze-dried fruits.