Betanin, a Natural Food Additive: Stability, Bioavailability, Antioxidant and Preservative Ability Assessments

Abstract

Betanin is the only betalain approved for use in food and pharmaceutical products as a natural red colorant. However, the antioxidant power and health-promoting properties of this pigment have been disregarded, perhaps due to the difficulty in obtaining a stable chemical compound, which impairs its absorption and metabolism evaluation. Herein, betanin was purified by semi-preparative HPLC-LC/MS and identified by LC-ESI(+)-MS/MS as the pseudomolecular ion m/z 551.16. Betanin showed significant stability up to -30 °C and mild stability at chilling temperature. The stability and antioxidant ability of this compound were assessed during a human digestion simulation and ex vivo colon fermentation. Half of the betanin amount was recovered in the small intestine digestive fluid and no traces were found after colon fermentation. Betanin high antioxidant ability was retained even after simulated small intestine digestion. Betanin, besides displaying an inherent colorant capacity, was equally effective as a natural antioxidant displaying peroxy-radical scavenger ability in pork meat. Betanin should be considered a multi-functional molecule able to confer an attractive color to frozen or refrigerated foods, but with the capacity to avoid lipid oxidation, thereby preserving food quality. Long-term supplementation by beetroot, a rich source of betanin, should be stimulated to protect organisms against oxidative stress.

Keywords: antioxidant ability; beetroot; betalains; ex vivo colon fermentation; in vitro human gastrointestinal digestion; malonildialdehyde; semi-preparative RP-HPLC.

Figure 1

Betanin separation by high-performance liquid chromatography diode array detector (HPLC-DAD) monitored at 536 nm. (A) Betanin standard chromatographed in the analytical HPLC column, (B) fresh beetroot juice sample chromatographed in semi-preparative HPLC, (C) betanin purified by semi-preparative HPLC and separated using an analytical HPLC column and (D) betanin evaluated after 275 days of freezing and chromatographed using an analytical HPLC column. Betanin (peak 1) and isobetanin (peak 1’). The betanin chemical structure from red beet was reproduced from Cai et al. [19].

Figure 2

Identification of purified betanin by HPLC-ESI(+)-MS/MS. (A) betanin m/z 551 [M + H]⁺, (B) fragmentation of purified betanin m/z from the MS/MS of 551 [M + H]⁺.

Figure 3

Lipid oxidation in ground pork loin evaluated by the production of malondialdehyde (MDA) during 9 days of storage at 4 °C. Control H₂O-DD, BHA (buthylated hydroxyanisole), BHT (butylated hydroxytoluene), Betanin 2% (w/w). Data are expressed as the means ± SD of three independent determinations. Different letters indicate differences between days at a significance level of p < 0.01. The symbol * (p < 0.05) indicates differences compared to day 0. The symbol ** (p < 0.05) indicates differences compared to day 3.