## 3 Results and Discussion
It appears that the changes induced by the 100 MPa pressure occurred on the more stable pulp and, therefore, require a higher centrifugation speed to be detected. However, when the 150 MPa pressure is applied, the percentage of pulp decreases and the supernatant transmittance decreases, reflecting an increase in the stability of the juice cloud. At pH 6, the effect of HPH treatment is more pronounced following the same trend as at pH 5.5 when the pressure is 100 MPa but decreasing the percentage of pulp and increasing the transmittance when the pressure is 150 MPa. Moreover, in this case, the changes can be associated with an increase in the stability of the juice cloud. The particles remaining in suspension may be small enough to allow more light to pass through, thus confirming the increase in transmittance. One of the main applications of high homogenization pressures in fruit juices is to achieve pulp stabilization so that the pulp remains in suspension instead of settling [38]. In a study by [PERSON] et al. [25] analyzing transmittance in mandarin orange juices, it was observed that the turbidity of the juices increased when higher homogenization pressures were applied. [PERSON] et al. [39] observed the same effect in orange juice. In other cases, because of chemical changes and the increased contact surface between smaller particles generated by the application of high homogenization pressures, they may aggregate and precipitate more easily, decreasing the stability of the juice cloud [37; 40]. The decrease in the percentage of pulp observed at a pressure of 150 MPa in the lulo juice makes it possible to rule out this phenomenon. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & & & **pH** & **Bix** & \(\rho\) (g/cm\({}^{3}\)) & **\%. Pulp** & **Transmit. ** & **\% Pulp** & **Transmit. ** \\  & & & pH & **Bix** & \(\rho\) (g/cm\({}^{3}\)) & **365\(\times\)\(g\)** & **365\(\times\)\(g\)** & **3000\(\times\)\(g\)** & **3000\(\times\)\(g\)** \\ \hline \multirow{4}{*}{ \begin{tabular}{} \end{tabular}  } & N-HPH & pH 5  
It is widely referenced in scientific literature that during HPH treatment in fruit juices, shear stress causes the disruption of suspended particles and a reduction of particle size. Moreover, different works have described an asymptotic behavior; higher pressures cause less and less changes in particle diameter [37; 41]. Thus, it indicates that disruption occurs preferentially in larger particles and cell clusters, with the small particles and cell fragments less susceptible to subsequent disruptions. This effect has been verified in lulo juice after evaluating the particle size distribution by using light scattering technique (Table 2). pH, HPH treatment, and fermentation had a significant effect on all parameters related to particle size. However, the most important changes were due to the HPH treatment; all parameters decreased as HPH pressure increased. pH and fermentation had a much weaker effect, slightly decreasing particle size. The data shown in Table 2 correspond in all cases to monomodal distribution curves with a single peak and a similar narrow distribution. The maximum corresponds to a diameter of about 210 \(\upmu\)m, 105 \(\upmu\)m, and 93 \(\upmu\)m for the samples non-homogenized and those homogenized at 100 and 150 Mpa, respectively. These values decreased to about 200 \(\upmu\)m, 100 \(\upmu\)m, and 90 \(\upmu\)m after fermentation with _Lactobacillus reuteri_. Although other authors [37; 41] observed narrower distributions with increasing homogenization pressure, this effect was not observed for lulo juice. It is probable that the filtration step in the processing provided a more homogeneous juice as compared to non-filtered fruit juices. Table 3 shows the results of the CIE-L*a*b* coordinates and the psychometric \(\text{h}^{*}\text{ab}\) and \(\text{C}^{*}\text{ab}\) coordinates of the lulo juices before and after fermentation and as a function of homogenization pressure applied and pH.