Dry mixing of food powders: Effect of water content and composition on mixture quality of binary mixtures
4. Conclusions
Mixture composition did not affect the mixing characteristics of sugar/salt and paprika/salt mixes in the range of 20–80% salt content, however the mixture quality dis-improved at the lower salt concentrations of 1% and less. For oregano/salt, there was a progressive dis-improvement in mixture quality with higher oregano content due to greater void spaces between particles which facilitated salt segregation by sieving. The results showed that composition has a greater influence on the MQ of powders that are more difficult to mix, such as O/S. Increasing the water content of the paprika and oregano, by exposing to high relative humidities, did influence the mixture quality of the mixes, but in different ways. For paprika/salt, the mixing became more difficult and this was most likely due to increased cohesiveness of the paprika at higher water content. On the other hand, the mixture quality of the oregano/salt improved when oregano had higher water content. This is most likely because of the increased cohesion of the oregano whereby the salt particles bound onto and coated the bigger oregano particles which inhibited the segregation tendency of the mix. Exposing the salt to 74% relative humidity resulted in a large increase in the cohesiveness of the salt due to water sorption, which made it difficult to mix with either the paprika or oregano. It is clearly seen that flowability of the powder also plays a crucial role to determine its ability to mix.