Food hydrocolloids κ-carrageenan and xanthan gum in processed red meat modify gut health in rats

Abstract

The food hydrocolloids κ-carrageenan and xanthan gum, used in processed foods including meat products, have unclear effects on gut health. This study investigated the effects of incorporating 1 % κ-carrageenan or xanthan gum into pork on protein digestibility, gut microbiota, oxidative stress, and gene expression using both in vitro gastrointestinal digestion/fermentation and an in vivo rodent model. In vitro, xanthan gum reduced protein digestibility (-11 %) in the simulated small intestine, thus elevating protein fermentation metabolites (up to 4-fold), but this was not observed in vivo. Consumption of a low-fiber pork diet without hydrocolloids promoted Akkermansia (29.5 % median abundance) and Tannerellaceae (24.7 %) growth in the colon, whereas κ-carrageenan increased Desulfovibrio (7.95 %) and Alistipes (6.14 %), and xanthan gum enhanced unclassified Muribaculaceae (14.8 %) and Bacteroides (12.1 %). Unexpectedly, transcriptomic analysis revealed a down-regulation of gut inflammatory pathways, accompanied by lower fecal calprotectin levels, in rats consuming pork with hydrocolloids. While κ-carrageenan notably reduced lipid oxidation in stomach contents, only xanthan gum lowered plasma and colonic oxidative stress. These findings highlight the potential of hydrocolloids to modulate dietary responses, suggesting a role in influencing gut health following high processed meat consumption.

Keywords: Akkermansia; Food additives; Gut microbiota; Pork; Protein digestibility.

Graphical abstract

Fig. 1

Protein digestibility and fermentation metabolites after in vitro digestion and fermentation of pork without (Pork, grey) or with κ-carrageenan (κ-CGN, orange) or xanthan gum (XNT, green). Each treatment was tested using fecal inocula from 3 individual donors, with 4 technical replicates per donor. As the heating condition had no significant effect, results were pooled (total n = 24 per treatment). Protein digestibility and H₂S levels were analyzed following a mixed model ANOVA procedure with the fixed factor ‘Additive’. Tukey-adjusted post hoc tests were performed for pairwise comparisons. For sulfur and protein metabolites, a non-parametric Kruskal-Wallis test with pairwise comparisons was performed using the effect ‘Additive’. Significant p-values were adjusted by the Bonferroni correction for multiple tests.

Fig. 2

Average feed intake and body weight of rats throughout the feeding period, and final body weight, heart weight and kidney weight in rats fed pork, pork with κ-carrageenan (κ-CGN) or pork with xanthan gum (XNT), (n = 10 per treatment). For feed intake and body weight, a repeated-measures ANOVA procedure with ‘rat ID’ as a random factor and ‘feeding day’ as a repeated effect was used to test significance. For the rest, a mixed model ANOVA procedure was used with the fixed effect ‘Additive’. Tukey-adjusted post hoc tests were performed for pairwise comparisons.

Fig. 3

Colonic microbial characterization. A Bacterial density and α-diversity (Shannon index and Inverted Simpson indices) in rats fed pork (grey), pork with κ-carrageenan (κ-CGN, orange) or pork with xanthan gum (XNT, green). B PCoA plot based on Bray-Curtis dissimilarity. C Relative microbial abundance at the phylum and family levels, showing individual animals (left bars) and treatment medians (right bars). D Cladogram from the LEfSe analysis, identifying taxa with significant variations among diets (LDA = 4). E Network analysis of bacterial genera with strong correlations (|r| ≥ 0.5), indicating positive correlations in blue and negative correlations in red. For bacterial density (median with 95 % confidence interval) an independent samples Kruskal-Wallis test with pairwise comparisons was performed, using the effect ‘Additive’ as an independent variable. Significant p-values were adjusted by the Bonferroni correction for multiple tests. For Shannon and Inverted Simpson, a mixed model ANOVA procedure was used, with the fixed effect ‘Additive’, and the random factor ‘euthanasia day’. Tukey-adjusted post hoc tests were performed for pairwise comparisons.

Fig. 4

Oxidative stress, inflammation markers and metabolites in blood, stomach, cecum and colon mucosa and feces in rats fed pork (grey), pork with κ-carrageenan (κ-CGN, orange) or pork with xanthan gum (XNT, green). For all parameters – except calprotectin – a mixed model ANOVA procedure was used, with the fixed effect ‘Additive’, and the random factor ‘euthanasia day’. Tukey-adjusted post hoc tests were performed for pairwise comparisons. For calprotectine, an independent samples Kruskal-Wallis test with pairwise comparisons was performed, using the effect ‘Additive’ as an independent variable. Significant p-values were adjusted by the Bonferroni correction for multiple tests.

Fig. 5

Significant up- or down-regulated KEGG pathways in the colon of rats fed pork with κ-carrageenan (left graph), or xanthan gum (right graph) sorted by logPAdj.