ABSTRACT
Plants possess a unique richness and a variety of metabolites, including organic acids, sugars, polyols, and amino acids as the main metabolites. Organic acids occur naturally in many plant and animal substrates and can, therefore, either be naturally present as components of foods due to normal biochemical metabolic processes, or due to direct addition as acidulants, hydrolysis, or bacterial growth, or later be added directly or indirectly to products (Gomis, 1992). These compounds are involved in various fundamental pathways in plant metabolism and catabolism as intermediate or end products. Citric, malic, succinic, fumaric, and oxalic acids play a key role in the Krebs cycle, which is the central energy-yielding cycle of the cell, taking part in the most important metabolic pathway of carbohydrates, lipids, and proteins (Bennet-Clark, 1993). Some serve as precursors for a variety of products, such as acetate in lipid synthesis or formate in the C1 metabolism. Others, such as malate, are involved in respiration and photosynthesis. Detoxication or incorporation of vital metals bring into play chelating agents such as oxalate or citrate.
