## 3 Results and Discussion
[42] found the same effect on phenols and flavonoids in orange juice. The results for the antiradical capacity (DPPH and ABTS methods) followed a similar trend as for phenols and flavonoids. The ABTS and DPPH methods determine the antiradical capacity of compounds with different hydrophilic nature: the ABTS radical reacts with compounds of a more hydrophilic nature than the DPPH radical. However, the great diversity of components of different nature with antiradical capacity existing in the juice of lulo resulted in high values in both cases. Moreover, [PERSON] et al. [17] determined the profile of phenolic compounds by liquid chromatography coupled with mass spectroscopy and showed a considerable increase in the diversity of phenolic compounds when applying a homogenization treatment to lulo juice. Considering that the antioxidant capacity of a mixture is not only given by the sum of the antioxidant capacities of each of its components, since the compounds interact with each other and can produce synergistic or inhibitory effects, it would be possible that the increase in the diversity of phenolic compounds is associated, in lulo juice, with an increase in the antiradical capacity of the juices when applying the HPH treatment. After juice samples fermentation, a significant improvement in the antioxidant properties of the juices was observed. Both total phenol and flavonoid contents increased after the fermentative action of _Lactobacillus reuteri_. Similar results were obtained by [PERSON] et al. [43], who found that _Lactobacillus_ increased the content of total phenols in cereals by 30%. The  
Figure 3: Total phenols content, flavonoids content, and antiradical capacity by DPPH and ABTS methods of the lulo juices before and after fermentation and as a function of homogenization pressure applied and pH. Solid bars represent juices at pH 5.5 and the striped bars represent juices at pH 6. Different letters denote statistically significant differences (\(p\leq 0.05\)). results were attributed to the release of phenols that were physically or chemically trapped in the soluble and fermentable fiber of the feed. The antiradical capacity determined by both DPPH and ABTS methods also experienced a significant increase after fermentation, being more evident for the results obtained by ABTS. This increase was positive with the homogenization pressure applied and more pronounced at pH 5.5 than at pH 6. In addition to the release of components with anti-radical activity and the generation of secondary metabolites in the fermentation process, the microbial cells themselves may have contributed to the increased antiradical capacity. Although there are no studies demonstrating this activity for _Lactobacillus reuteri_, there is strong evidence of the antioxidant activity of _Lactobacillus plantarum_, _Lactobacillus hevticus_, _Lactobacillus acidophilus_, _Lactobacillus fermentatum_, _Lactobacillus casei_, and some bifidobacteria strains [44]. Effect of Gastrointestinal Digestion on the Viable Cell Content in Lulo Jucies at Different pH and Homogenization Pressures  
Figure 4 includes viable cell counts and survival rate (Rs) (calculated as explained in Section 2.5) of _Lactobacillus reuteri_ along gastric and intestinal stages of the in vitro simulated gastrointestinal digestion process for all the fermented lulo jucies. Analysis of variance (\(p\leq 0.05\)) showed that both the initial pH and the homogenization pressure had a significant effect on the survival of _Lactobacillus reuteri_ to the in vitro simulated gastrointestinal digestion process. Furthermore, there was a significant interaction between the two factors. In all cases, the increase in acidity and the presence of pepsin associated with the beginning of the gastric stage caused a decrease in the number of viable cells of up to 1.5 log units. However, at the end of this stage, the viable cell content remained almost constant in the juices subjected to the HPH treatment, and slightly decreased in the case of non-homogenized ones.