Microencapsulated Vitamin A Palmitate Degradation Mechanism Study To Improve the Product Stability.

By using a high-resolution mass spectrometer, four vitamin A palmitate (VAP) degradants were identified from microencapsulated VAP degradation samples. Based on the degradants, VAP first breaks down into anhydroretinol (ANHR) and palmitic acid (PA) through ester thermal elimination (ETE). Sequentially, the formed ANHR reacts with remaining VAP to ANHR-VAP and with a second ANHR to ANHR-ANHR. The migration of H+ in the transition state predicts that the H+ concentration in media will affect the ETE. Based on the degradation mechanism discovered from this study, a new product was developed and its media pH changed from 4.2 to 6.2. The new microencapsulated VAP degraded from 22.3% to 4.8% on an annualized basis. In the VAP degradation, no oxidized apo-carotenoids were found. The oxidized apo-carotenoids were detected in the degradation of ß-carotene, a pro-vitamin A, through natural oxidation by oxygen in air. This indicated that, in ambient and dry conditions on its own, VAP decay was unlike that of ß-carotene through natural oxidation.

Identification of Beta-Carotene Degradation Compounds and Their Structural Elucidation by High-Resolution Accurate Mass Spectrometry.

Beta-carotene (BC) degradation was studied by liquid chromatography coupled to a quadrupole time of flight mass spectrometer. Throughout/After 21 days of dark storage, 56 nonvolatile degradants were chromatographically separated from pure BC crystal and their molecular formulas were identified. Their structure information was gained by comparing the fragments to a different, but structure-related compound. For example, a newly formed double bond position in dehydrogenated BC was determined by comparing the fragments between BC and dehydrogenated BC. One of their chemical structures was confirmed by comparing its precursor ion mass, retention time, isotopic ratio, and fragmentation to a pure trans-beta-apo-8'-apocarotenal. BC cleavage was observed on double bonds as well as single bonds in BC conjugation chain. PRACTICAL APPLICATION: As evidenced in this study, beta-carotene (BC) degradation is a spontaneous process initiated when the compound is exposed to air. The stoichiometric ratio of BC to oxygen is 1:0.03 at the first oxidation, therefore, only 0.3 mg oxygen or 1.2 mL air will degrade 10 mg BC, an average daily recommended intake. Not like in enzymatic BC degradation, spontaneous BC oxidation did not produce provitamin A, either in retina C20H38O or retinol C20H40O forms. For BC application in vitamin A deficiency, spontaneous BC oxidation should be avoided.