Agglomeration of soy protein isolate in a pulsed fluidized bed: Experimental study and process optimization

• The optimal conditions to obtain agglomerated soy protein isolate have been established.
• The mean diameter of agglomerated soy protein was 130% larger than the initial size.
• Agglomerated particles were more porous and had a more irregular shape.
• The agglomeration process improved appearance, flowability, and wettability.
• The agglomeration also improved the functional properties of the product.

The soy protein isolate contains a high amount of protein and small fractions of fat, carbohydrates, and fiber. The food industry often employs this isolate as an additive, despite its drawbacks: it is a cohesive powder; its fluidization culminates in cracks and channeling. In this paper we used the experimental design to establish the optimal operational conditions to produce agglomerated soy protein isolate in a pulsed fluidized bed. The bed operated with an air pulsation frequency of 600 rpm; the liquid binder consisted of an aqueous carboxymethyl cellulose solution. We employed a 23 complete factorial design with three central points to evaluate how the variables fluidizing air temperature (60–80 °C), fluidizing air velocity (0.51–0.67 m s− 1), and binder flow rate (1.2–2.0 mL min− 1) affected the mean particle diameter, process yield, and moisture content. Surface response analysis pointed out the operational parameters that provided large granules with low moisture content and high process yield. Compared with the raw isolate, the agglomerated particles were more porous and irregular; they also presented good handling properties, reduced wetting time and cohesiveness, and improved free-flow. Moreover, agglomeration enhanced the functional properties of the powder such as water retention and foaming capacity.

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