C: Food Chemistry Effects of L-Ascorbic Acid on Physicochemical Characteristics of Wheat Starch Mahsa Majzoobi, Mohsen Radi, Asgar Farahnaky, and Tawee Tongdang Abstract: The main objective of this study was to determine the effects of l-ascorbic acid, as a permitted additive in bakery products, on characteristics of wheat starch. Suspensions of wheat starch (30%, w/w) in water containing 140 mg/kg ascorbic acid before and after gelatinization were prepared and studied using different techniques. The results of scanning electron microscopy showed that some spots appeared on the surface of the starch granules as a result of the addition of ascorbic acid. However, no changes in the starch crystalline pattern and its degree of crystallinity were observed by X-ray diffraction technique. For ungelatinized samples, no difference in the pasting properties of the samples was determined by the rapid visco analyzer, whereas for the gelatinized samples, peak and final viscosities decreased for the samples contained ascorbic acid. Determination of the intrinsic viscosities of the samples showed that addition of ascorbic acid to the gelatinized samples reduced the intrinsic viscosity. In general, it was found that ascorbic acid had some degradation effects on wheat starch molecules particularly after gelatinization. Keywords: l-ascorbic acid, molecular structure, physicochemical properties, wheat starch Practical Application: Understating the effects of ascorbic acid on wheat starch functionality is important in food industry. Ascorbic acid is more effective on wheat starch after gelatinization. Ascorbic acid may have degrading effect on wheat starch reducing the consistency of the medium. Introduction Starch is a great part to the food nutrition value, texture, and overall quality (Copeland and others 2009). The functionality of starch in a food system may be affected by the components present in the food. Therefore, understating the effects of food components on the physicochemical properties of starch is of great importance. Although the effects of usual food components including lipids (Tang and Copeland 2007), hydrocolloids (Funami and others 2005; Kohyama and Nishinari 2006), proteins (Considine and others 2011), sugars (Carvalho and Mitchell 2001), and salt (Farahnaky and others 2009) have been studied previously, there is still a lack of information on the effects of food additives on starch properties. Food additives such as chlorine as a bleaching and improving agent for wheat flour, can affect pasting properties of starch (Pomeranz 1984). Effects of sour seasonings on the rheological properties of cornstarch pastes were studied by steady shear and dynamic oscillatory viscoelasticity measurements, intrinsic viscosity measurements, and microscopic observation (Hirashima and others 2005). It became clear that addition of these substances caused amylose and amylopectin chains to hydrolyze and led to the decrease in the viscosity at low pH values. l-cysteine, a permitted bread dough improver, can affect wheat starch particularly after gelatinization (Majzoobi and others 2011). MS 20111081 Submitted 9/9/2011, Accepted 11/26/2011. Authors Majzoobi, Radi, and Farahnaky are with Dept. of Food Science and Technology, School of Agriculture, Shiraz Univ., Shiraz, Iran. Author Tongdang is with Food Science and Nutrition, Prince of Songkhla Univ., Pattani Campus, Pattani, 9400, Thailand. Direct enquiries to Majzoobi (E-mail: majzoobi@shirazu.ac.ir). One of the acceptable food additives is l-ascorbic acid (AA), an important source of vitamin C, which exists naturally in many vegetables and fruits and is used as an antioxidant. It is generally added in bakery products (up to 200 mg/kg of wheat flour) to improve dough and bread quality (Pomeranz 1984). Depending on the conditions, AA can act as an oxidative or a reducing agent. The oxidative effects of AA on wheat gluten are well established and it is generally believed that AA can increase dough strength and stability and hence is beneficial for weak flours. Under vac- uum condition (for example, vacuum dough mixers), however, AA acts as reducing agent and can reduce disulfide bonds in the gluten network and weaken the dough. Such effect may be advan- tageous to improve the quality of very strong dough (Pomeranz 1984). Although the effects of AA on proteins (particularly gluten) have been studied, there is lack of information on the possible ef- fects of AA on starch which requires further investigations. AA is a highly reactive agent, which can be easily oxidized and form free radicals which are capable of decomposing polysaccharides (Kivel¨ a and others 2009; Paquet and others 2010). Paterson and others (1996) and Valles-Pamise and others (1997) showed that addition of AA to starches caused changes to their pasting prop- erties. Sriburi, and others (1999) reported the degradation effects of AA on cassava starch. Kivel¨ a and others (2009) found that ad- dition of 0.01 mol/L AA reduced the molecular weight of barley β -glucan. The main goal of this research was to determine the effects of AA on some physicochemical characteristics of wheat starch as the main component of wheat flour. The results of this study may be useful to obtain better understanding of the improving mechanism of AA in bakery products based on wheat starch. C  2012 Institute of Food Technologists R  C314 Journal of Food Science  Vol. 77, Nr. 3, 2012 doi: 10.1111/j.1750-3841.2011.02586.x Further reproduction without permission is prohibited