NFS 40,5 504 Nutrition & Food Science Vol. 40 No. 5, 2010 pp. 504-514 # Emerald Group Publishing Limited 0034-6659 DOI 10.1108/00346651011077018 Effects of cooking methods and processing stages on vitamin C in traditional Lebanese meals Antoine G. Farhat and Talar M. Fossian Faculty of Nursing & Health Sciences, Notre Dame University, Zouk Mosbeh, Lebanon Abstract Purpose – Lebanese meals rich in vitamin C are taken for granted to contain this vitamin without consideration of its losses during the cooking and storing processes. This paper aims to examine the impact of different cooking pots, refrigeration and conventional reheating or via microwaving (MWR) on vitamin C depletion. Design/methodology/approach – Two samples of three meals rich in vitamin C (AB: Aadas Bhamoud made of lentils and Swiss chard; CS: cauliflower stew; ML: Meloukhieh made of Jew’s mallow) were analyzed in triplicates when they were raw, cooked in double based stainless steel (DBSS) or pressure cookers (PCs), refrigerated at 4  C for 48 h, and when reheated in an open pot or in a microwave reaching 70  C. The titration with 2,6-dichlorophenolindophenol method was used for vitamin C analysis. Findings – Relative vitamin C losses throughout the processing stages were 37.64, 65.43 and 79.00 percent for ML, CS and AB, respectively. DBSS tended to deplete vitamin C less than PC. AB lost 34.4 and 49.2 percent vitamin C with DBSS and PC, respectively; CS lost 52.3 and 57.5 percent with DBSS and PC, respectively; and ML lost 16.3 and 27.4 percent with DBSS and PC, respectively. Vitamin C loss at refrigeration was significant for both cooking pots used for the meals AB and ML but not for CS. Reheating resulted in further significant losses across meals and reheating methods. Practical implications – The study highlights the importance of avoiding unnecessary cooking practices to minimize vitamin C depletion and more accurately estimating its daily intake. Originality/value – The study presents for the first time the quantification of vitamin C losses in Lebanese meals subjected to different processing types and stages. Keywords Lebanon, Cooking, Refrigeration, Vitamins, Nutrition Paper type Research paper Introduction Vitamin C or ascorbic acid (AA) is one of the most unstable vitamins to the extent that it is considered as an index of quality of cooked vegetables (Fillion and Henry, 1998; Les ˇkova ´ et al., 2006). The two main factors that affect the amount of vitamin C in foods are oxidation and leaching out. It is unstable in aqueous solution where it gets oxidized by chemical compounds and enzymes (Bhagavan, 2002). In a medium of controlled temperature, water activity and air of food systems, the degradation of AA was found to be greater under excess oxygen (Dennison and Kirk, 1978). Some foods contain within their tissues an amount of oxygen sufficient to be a factor in the oxidation process, and small amounts of copper coming from utensils and containers catalyze or speed up the oxidation of vitamin C in the presence of air (Munsell, 1940). The rate of AA destruction in tomato juice was determined as a function of copper concentration where it increased as copper concentration in tomato juice increased (Lee et al., 1977). Ascorbic acid oxidase catalyzes dioxygen reduction to water using AA as the electron donor and its activity was found to be proportional to light intensity (De Tullio et al., 2007). The rate of AA destruction was influenced by pH (Lee et al., 1977). The comparison of frozen, steamed, tray-line and delivered peas between two hospital foodservice systems showed that AA loss was higher in the hospital that had higher The current issue and full text archive of this journal is available at www.emeraldinsight.com/0034-6659.htm