Surface ModificationTo Reduce Deposition Flux of Spray Dried Noni (Morinda Citrofolia L.) Juice

Abstract

ABSTRACT: Spray drying is widely spread technique for drying of liquid products especially fruit juices such as noni juice. However, during spray drying of noni juice stickiness problem commonly occurs due to low molecular weight sugars (sucrose, glucose and fructose). The aim of the present research was to determine the impact of Teflon surface modification on the yield of spray dried Noni juice and deposition flux. Different exposure time of feed spray was undertaken prior to adhesion flux weight determination. Three different sets of inlet temperature (100 oC, 150 OC and 190 oC) and exposure times (of 15 min, 30 min, 60 min, 75 min, 90 min and 115 min) were tested. Samples were evaluated for contact angle, weight of adhesion flux, hygroscopicity and moisture content. There was a sudden increased in deposition flux (p<0.05) as the temperature increased. At 150 and 190°C, the weight of deposition flux was not significant (p>0.05) for both plate materials. The borosilicate plates (BP) registered up to 80% deposit removal whilst Teflon plate (TP) recorded only 20%. Physical observation of the Teflon plates showed that some areas of the plate (100 °C) were fully clear from any particles. Nevertheless, for the borosilicate glass plates, the primary adhered particles tend to retain and smeared along the plates. In addition, there was a substantially negative relationship between the contact angle and adhesion weight, (r = -0,924, p<0.01). The negative connection suggests that by increasing the contact angle, the adhesion weight will decrease and vice versa. The contact angle of the Teflon (PTEFE) surface was approximately 117.2 ± 1.4°, which provided an excellent hydrophobic surface. In this research, the powder with the lowest amount of hygroscopicity was gained at 190 oC using the Teflon plate. For that reason, surface modification was indeed amplified the surface hydrophobicity thus decreasing the deposition flux.