Development and application of biopolymer coatings to specialty green coffee beans: Influence on water content, color and sensory quality

Edible biopolymers are used as barrier coatings to preserve food products quality, but they have never been studied for use with green coffee beans. In the present work, biopolymeric coatings were developed and characterized in order to determine the treatment that would best retain the physical and sensorial properties of green coffee beans. The factors investigated were the type of biopolymer (starch and chitosan), pre-drying time (1 and 3 h) of the suspensions in an oven, and the number of immersions (1 and 2) of the green coffee beans in the suspensions. Tests were performed on coated beans (color and water content), films (contact angle with water and moisture), suspensions (rheological behavior after pre-drying), and beverages obtained from coated and roasted coffee beans (sensory quality). Contact angle and moisture analyses revealed that starch resulted in higher resistance to moisture than did chitosan treatments. Pre-drying for 3 h changed only the viscosity resulting from starch-based treatment. The treatment that entailed the use of starch, 3 h of pre-drying, and one immersion was the one that best retained color and water content characteristics of coated green coffee beans compared to control (uncoated green coffee beans). Moreover, neither biopolymer altered the sensory quality.