As can be observed, L* value was decreased for all the HPP treatments
applied, obtaining a higher decrease at the higher pressure
and longer time range. These results were in accord to those previously
reported by Barba, Cortés, Esteve and Frígola (2012) in HPP orange
juice mixed with milk. These authors attributed it to partial
precipitation of unstable particles in the juices after processing.
With regard to a* values, the behavior was different depending on
Stevia concentration of the untreated samples. The reduced regression
model presented in the Eq. (9) allowed for prediction of the effects
of independent variables on the a* values: