CHALLENGES IN ALVEOLI FORMATION AND CRUST AND CRUMB COLORATION WHEN USING NOPAL AS A STRATEGY FOR GLUTEN-FREE AND GLUTEN-CONTAINING BREAD

The forage palm flour (NF) (Opuntia ficus-indica) is rich in hydrocolloids and has potential for use in baking. This study aimed to evaluate the performance of forage palm flour in gluten-free and gluten-containing bread. The breads were made with a control formulation (C) based on wheat flour (CWG) or rice flour (CGF), with a partial substitution of 8% (m/m) by NF (NWG and NGF for breads with and without gluten, respectively). The evaluated responses included instrumental color of the crust (st) and crumb (mb) (luminosity-L* and whiteness index-WI, browning index-BI, greenness index-GI, yellowness index-YI, redness index-RI, and color index-CI), and crumb image characteristics (total slice area-STA, number of alveoli-NA, total alveoli area-ATA, average alveoli size-AAS, alveoli area percentage-AAP, and alveoli circularity-AC), assessed by Student's t-test and multivariate analysis (P<0.05). The univariate analysis showed that the main differences were observed between CGFxNGF and CWFxCGF, with only crumb alveolar characteristics being distinct for NWGxNGF. The largest differences were observed between CWGxCGF, for which only GI did not show a difference. Multivariate analysis through the dendrogram confirmed this behavior, with three clusters observed, unifying the samples using NF. Principal component analysis indicated that NF had a greater impact on the responses GI-st, GI-mb, YI-mb, and BI-mb, with the alveolar quality being enhanced by wheat flour in the gluten-containing breads (PC1) and by NF in the gluten-free breads (PC2). When evaluating the results through Partial Least Squares Discriminant Analysis, it was observed that the Variable Importance in Projection was higher for L-mb, GI-mb, YI-mb, AAP, and ATA, indicating that NF had a greater impact on the crumb characteristics when compared to the crust. On the other hand, MAS, AC, RI-mb, and CI-mb did not show a significant effect. The heatmap was consistent with the dendrogram, resulting in three clusters, with the greatest effects observed in GI, YI, and BI, likely due to the carotenoid and chlorophyll content in NF and the Maillard reaction and caramelization during baking. Pearson's correlation indicated that the crumb alveolar characteristics were better in the gluten-containing breads concerning STA and AC, but the use of NF showed a better effect in gluten-free breads. The results demonstrate a positive effect of the hydrocolloids in NF regarding the mimicry of the gluten network, showing better technological performance. In general, it was observed that in formulations without the use of chemical additives, NF exhibited better performance in gluten-free breads.