Susceptibility of 5-methyltetrahydrofolic acid to heat and microencapsulation to enhance its stability during extrusion processing Ashok K. Shrestha a,⇑ , Jayashree Arcot b , Sri Yuliani c a Centre for Nutrition and Food Sciences, University of Queensland, St. Lucia, Queensland 4072, Australia b Food Science and Technology, School of Chemical Sciences and Engineering, The University of New South Wales, Sydney 2052, Australia c Indonesian Center for Agricultural Postharvest Research and Development Jl, Tentara Pelajar 12, Bogor 16114, Indonesia article info Article history: Received 9 February 2011 Received in revised form 29 April 2011 Accepted 13 July 2011 Available online 21 July 2011 Keywords: Folates Thermal degradation Fortification Microencapsulation Extrusion abstract Folic acid is a common form of folate used for food fortification to prevent the incidence of neural birth defects among others. However, 5-methyltetrahydrofolic acid (5-MTHF) is considered, a better alterna- tive to folic acid and is less likely to mask the symptoms of B 12 deficiency in older populations. Also it is less bioavailable, and present in very low amount in foods. Fortification of foods with 5-MTHF is con- sidered problematic, because it is highly sensitive to normal food processing operations. A comparative study on the thermal stability of folic acid and 5-MTHF in various liquid model food matrices such as milk, soymilk, starch–water and water during boiling and autoclaving at various time intervals was per- formed. Thermal degradation of 5-MTHF was more severe than folic acid in all food matrices e.g., almost 70% loss of 5-MTHF vs 17% loss of folic acid. Microencapsulation of 5-MTHF is considered to improve the stability of 5-MTHF during processing. A combination of pectin (P) and sodium alginate (A) at three dif- ferent proportions (P60:A40, P70:A30, P80:A20) were employed for encapsulating 5-MTHF by spray dry- ing. Microcapsules with the highest loading efficiency of 60% of vitamin (from P80:A20) and unencapsulated 5-MTHF powder was incorporated into starch and extruded at six different temperatures (100, 110, 120, 130, 140, 150 °C). The 5-MTHF had better stability (84–94.5% retention) compared to the free form (65.3–83.2%) in all extruded products. The effectiveness of encapsulation was more evident at higher extrusion temperatures. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Folate acts as a coenzyme substrate in many reactions of amino acids and nucleotides. The reduced forms of folates serve as an acceptor or donor of a single carbon unit, a reaction collectively called ‘single carbon metabolism’. The presence of genetic defects in normal folate-dependent metabolic processes involving DNA synthesis, has been linked to cancer initiation (Fenech, 2001). Folate deficiency in the diet has been linked to malformation of the embryonic brain/spinal cord development, a condition referred to as neural tube defects or NTDs (manifested by still-birth, mental retardation, swollen head, and poor bladder control) (Czeizel & Dudas, 1992; Medical Research Council (MRC) Vitamin Study Research Group, 1991). Recent data has showed that there are around 338 incident cases of NTDs a year in Australia (FSANZ, 2006). Folate deficiency is also linked to the accumulation of plasma homocysteine levels, a strong predictor of carotid artery narrowing which is a predictive risk for both stroke and atherosclerosis (Sel- hub et al., 1995). Folate exists in a significant amount in green leafy vegetables, fruits, legumes, fermented vegetables, egg yolk while most cereals and their flours are poor sources of folate (Shrestha, Arcot, & Paterson, 2003). Considering the significant number of NTD cases, fortification of cereal based foods with folic acid (syn- thetic form) has been made mandatory in 57 countries including the USA and Australia. Among 100 folate compounds, folic acid and 5-methyl-5,6,7,8- tetrahydrofolic acid, are the most commonly reported forms (Fig. 1, Gregory, 1989). The presence of folic acid is almost non-existent in plant and animal foods whereas 5-MTHF, 5-formyl- tetrahydrofolate, 10-formyltetrahydrofolate and other reduced folates are more abundant (Ginting & Arcot, 2004). Bioavailability of folic acid from fortified foods is reported to be different from naturally available folates (Wright, King, Wolfe, Powers, & Finglas, 2010). The use of folic acid as a fortificant is often considered con- troversial as it can mask the haematological abnormalities of vita- min B 12 deficiency while the neurological complications remain in progress (NHMRC, 1995). There is now consideration for the use of 5-MTHF which cannot possibly mask the Vitamin B 12 deficiency as an alternative to folic acid (Wright, Finglas, & Southon, 2001). Folic 0308-8146/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2011.07.040 ⇑ Corresponding author. Address: Centre for Nutrition and Food Sciences, University of Queensland, St. Lucia, Brisbane, Australia. Tel.: +61 7 3346 9642; fax: +61 7 3365 1177. E-mail address: a.shrestha@uq.edu.au (A.K. Shrestha). Food Chemistry 130 (2012) 291–298 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem