High Hydrostatic Pressure Modulates the Folate and Ascorbic Acid Accumulation in Papaya (Carica papaya cv. Maradol) Fruit

High hydrostatic pressure (HHP) has previously induced de novo carotenoid (provitamin A) biosynthesis in papaya fruit tissue, possibly as a response to the oxidative stress. Papaya is also an excellent source of other vitamins, such as tetrahydrofolate (THF), its derivatives (folates, vitamin B9), and ascorbic acid (vitamin C). This work evaluated the immediate effects of HHP treatments (50–400 MPa for 3–60 min) on folate and ascorbic acid contents of fresh-cut papaya fruit. Folates and ascorbic acid were characterized by high-performance-liquid-chromatography with electrochemical and diode-array detections (HPLC-EC and DAD, respectively). Ascorbic acid levels increased in all conditions (4–28%) when compared with non-treated controls. 5-Methyl-THF (5-CH3-THF) (73%) and THF (22%) were the main folate species present in papaya fruit. HHP treatments increased 5-CH3-THF and total folate contents by 35% and 25%, at lower (50–100 MPa) and higher (400 MPa) pressures for 30 min, respectively. Folate molecule contains a glutamyl tail, involved in its function as a cofactor, tissue localization, and stability. 5-CH3-THF from papaya fruit exists with a very long polyglutamyl tail (Glu1–17). Both pressure and time increased concentrations of 5-CH3-THF Glu1 species (up to 250%), mainly at the 100 and 400 MPa/30 min conditions, whereas the polyglutamyl forms (Glu2–17) were not affected. Results documented, for the first time, that specific HHP treatments can positively modulate accumulation of vitamins B9 and C in papaya fruit.