Powder caking and cohesion behaviours of coffee powders as affected by roasting and particle sizes: Principal component analyses (PCA) for flow and bioactive properties

Abstract

Roasting degree and particle size are two major parameters that affect the mixture homogeneity of powdered food mixtures. This study focused on the flow properties of powdered coffees regarding their roasting degree (light and dark roasted) and particle sizes (0.1; 0.3; 0.5 mm) for aiming to assess the flow and physicochemical properties of coffee and the relationship with the bioactive, sensory properties and flowability. Since the powder caking of foods is highly undesirable due to the stoppage problems during the filling operation in process. Determination of the flow properties of the coffee are very important and the factors affecting the flow properties should be considered in detail. The flow behavior of coffee samples was characterized by powder rheometer with cohesion, caking and powder flow speed dependency (PFSD) tests. Principal component analysis (PCA) was applied in order to explore similarities and hidden patterns among samples. Results indicated that caking was not the case for medium and coarse coffee samples, yet fine grinded samples were subjected to caking. Increasing cake height ratio indicated the powder has a high tendency to form cake. Among the samples, only light coffee with larger particle size (CL) was flow stable since its flow stability value was closed to 1. Light coffee samples had higher 5-hydroxymethyl furfural (5-HMF) content than dark coffees while 5-HMF was not detected in green coffee grinds. There was an augmentation of antioxidant activity of samples with the increasing rate of 5-HMF. The dimension reduction method of PCA could provide beneficial information for the food industry for determining the effect of particle size and roasting degree on the powder flow characteristics. (C) 2018 Elsevier B.V. All rights reserved.