Impact of Iron Source and Concentration on Rice Flavor Using a Simulated Rice Kernel Micronutrient Delivery System

Cereal Chem. 81(3):384–388 An extruded grain designed to look like a rice kernel fortified with one of two sources of iron (elemental iron and ferrous sulfate), with and without multiple fortificant (zinc, thiamin, and folic acid), was mixed with milled Calrose rice at low (1:200), medium (1:100), and high (1:50) concentrations. The intensities of water-like, sour taste, hay-like musty, and alfalfa/grassy/green bean flavors were enhanced by the addition of ferrous sulfate (FeSO4) or FeSO4 plus multiple fortificants. Astringent mouthfeel was likewise affected by addition of FeSO4 or FeSO4 plus multiple fortificants. Overall, the elemental iron with multiple fortificants least affected the oxidation of the extruded kernals. Lipid oxidation products in stored fortificant increased the first two to three months and concentrations were higher in samples with FeSO4 as the iron source. Iron deficiency anemia is one of the most prevalent nutritional problems in the current world population. To combat this deficiency, nutritionists recommend iron fortification of foods. Fortification is more effective than supplementation because nutrients are incorperated into the regular diet, eliminating the problem of easily omitted or forgotten doses (Cook and Reusser 1983). Rice is a dietary staple for a major portion of the world’s population and is thus an obvious vehicle for iron fortification (Beck 1971). Iron availability varies according to the individual and the form of iron ingested. Pregnant women need more iron than menstruating women and both need more than men and menopausal women. Soluble ferrous iron salts (Fe) result in greater absorption than ferric salts (Fe). Insoluble ferrous salts (ferrous phosphate) have poor absorption, while soluble ferric salts (ferric chloride) have fair absorption. Ferrous sulfate is fairly efficient in treating iron deficiency anemia. Other sources of iron such as elemental or reduced iron are used in the food industry. It dissolves in the hydrochloric acid in the stomach. Therefore, the smaller the particle size, the greater the absorption (Waddell 1974). Both Fe and Fe forms of iron exhibited discoloration in extruded fortificant products unless acidity was increased before extrusion (Kapanidis and Lee 1996). Enrichment and fortification of rice can be accomplished in several ways. Currently, most processors of rice use powders and coated grains for enrichment. The powder consists of a preblended mixture of vitamins and minerals that is incorporated with the grains. However, rice rinsing removes the powder. Coated graintype fortification is an alternative method in which grains of rice are first coated with vitamins and minerals and then coated with a water-insoluble, food-grade material (Hoffpauer 1992). Another approach for enrichment or fortification is to make simulated grains containing the nutrients. In the late 1980’s, an extruded rice fortificant was developed primarily as a method to fortify rice with vitamin A (Lee et al 2000). The product is similar in shape to a rice grain and is added to rice at the 1/50 to 1/200 level. Two challenges with extruded rice fortificants are 1) to make it stable to oxidation and 2) to make it white enough so that it cannot be distinguished when diluted with milled rice (Murphy et al 1992). Iowa State University scientists and the Bon Dente Co. (Lynden, WA) collaborated to increase the stability of the product fortified with Vitamin A (Murphy et al 1992). Early attempts to co-fortify extruded rice fortificant with vitamin A and iron resulted in oxidation of vitamin A by the iron and subsequent discoloration of the product (Murphy 1996). The objective of this research was to determine how differing sources and amounts of iron fortificant affect the flavor of milled rice, as determined by descriptive analysis. The iron fortificant was an extruded kernel formulated with and without other micronutrients (zinc, folic acid, and thiamin). The combination of these micronutrients may increase oxidation. Therefore, oxidative stability was determined by gas chromatographic analysis of lipid oxidation products. MATERIALS AND METHODS Preparation of Fortified Rice The extruded premix grain-like kernels had five formulations: 1) multiple fortificant product without iron consisting of zinc, thiamin, and folic acid; 2) formula 1 with ferrous sulfate (FeSO4) as the iron source; 3) formula 1 with elemental iron (Fe) as the iron source; 4) FeSO4 alone; and 5) Fe alone. The ratios of premix to rice were 1:50 (high), 1:100 (medium), and 1:200 (low), with 1:100 representing the average target fortification (total of 15 treatment combinations). Each sample was presented twice. The ratios were mixed on a w/w basis. The high concentration mix was prepared with 12 g of premix to 588 g of rice. The medium concentration had 6 g of premix to 594 g of rice. The low concentration had 3 g of premix to 597 g of rice. The levels of nutrients added to this extruded kernel were thiamin (0.45 mg/100 kg), zinc (3.0 mg/100 kg), folic acid (0.15mg/100 kg), and iron (3.8 mg/100 kg). These concentrations are within the normal range of fortification for rice. The distribution in rice could vary from 1:50 to 1:200, depending on the rice consumption and needs of the target population and the micronutrient intake desired. Sensory Analysis Twelve panelists previously trained in the principles and concepts of descriptive analysis (Meilgaard et al 1999) participated in the study. The rice flavor lexicon employed was based on the work of Goodwin et al (1996) and Bett-Garber et al (2001) (Table I). It includes 12 unique flavor attributes. Flavor was determined by smelling and by evaluation in the mouth. The average of the most and least intense experience for an attribute in the sample was recorded. Intensity was rated using a 0–15 anchored universal intensity scale (Table II) with 0 indicating not detectable and 15 indicating more intense than most foods (Meilgaard et al 1999). Scores were recorded on a computerized ballot system (DSA-1989, Compusense, Guelph, ON, Canada) Each sample was presented to the panelists twice in separate sessions following the randomized design in which each session consisted of three experimental 1 SRRC, ARS, USDA, New Orleans, LA 70124. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable. 2 Corresponding author. Phone: 504-286-4459. E-mail: [email protected] Publication no. C-2004-0324-07R. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. American Association of Cereal Chemists, Inc., 2004.