Application of RVA and Time-Lapse Photography to Explore Effects of Extent of Chlorination, Milling Extraction Rate, and Particle-Size Reduction of Flour on Cake-Baking Functionality

Cereal Chem. 87(5):409–414 Three factors (extent of chlorination, milling extraction rate, and particle-size reduction) in cake-baking functionality of Croplan 594W flour were explored using a Rapid Visco-Analyser (RVA) and time-lapse photography. The extent of chlorination and milling extraction rate showed dramatic effects, but postmilling to reduce flour particle size was a less significant factor. RVA results showed that starch pasting was accelerated, and both peak and set-back viscosities were enhanced, with increasing extent of chlorination. These effects were exaggerated by the high sugar concentration relevant to cake baking, compared to the same effects in water. Cake baking with chlorinated flours, in a formulation with 50% sugar (%S) and 275 parts total solvent (TS), showed that, as the extent of chlorination increased, cake moisture content and edge height decreased. Cake center height and shape factor were curvilinear, with maxima near flour with pH 4.6. Dramatic collapse occurred for cakes baked with unchlorinated flour samples, due to delayed starch pasting, as documented by time-lapse photography and comparison to the geometry of the final cooled cakes. Starch pasting and egg white setting occurred too early for the cakes baked with excessively chlorinated flour (pH ≤4.0), but too late for the cakes baked with unchlorinated or insufficiently chlorinated flours (pH ≥4.9), compared to the ideal starch pasting and egg white setting behavior with appropriately chlorinated flours (pH >4.0 and <4.9). Informal sensory texture evaluation showed that cake mouthfeel was related to both moisture content per se and the relationship between moisture content and cake relative humidity (%RH). Excessive flour chlorination resulted in unacceptably dry cake mouthfeel. Chlorination is still an essential soft wheat flour treatment for production of high-ratio cakes in the United States and it is frequently coupled with a postmilling treatment to reduce flour particle size. The normal range of chlorination is 1,100–2,300 ppm, and the chlorinated flour generally has a pH in the range of pH 4.5–5.2 (Hoseney et al 1988). Kissell et al (1974) and Kissell and Yamazaki (1979) reported that the level of chlorination significantly affected cake volume, according to the extent of expansion and shrinkage during baking and cooling, and that optimum chlorination was a compromise between the amount of cake expansion and shrinkage. Flour particle size is another important factor in cake quality. Reduction of flour particle size by pin milling improved cake quality but excessive pin milling increased the extent of starch damage, resulting in deteriorated cake quality (Miller et al 1967). Yamazaki and Donelson (1972) also reported a high negative correlation between flour particle size index and cake volume. Generally, a high viscosity is required for cake batter to produce a better cake volume and a more uniform grain because of slowed gas diffusion, slowed migration of buoyant bubbles, and prevention of the settling out of starch granules in a more viscous system (Hoseney et al 1988). Gaines and Donelson (1982) used a modified viscograph technique to continuously measure cake batter viscosity of a complete cake formula at 20–100°C and showed that cake expansion during baking is significantly correlated with apparent viscosity of the batter. Cake batter viscosity is also influenced by fat content and emulsifier type; the increase in fat content and addition of emulsifier decreases the apparent viscosity (Sakiyan et al 2004). Among the effects on flour components due to chlorination, enhanced starch pasting is a critical factor linked to cake quality, because gelatinized or pasted starch networks prevent cake collapse and maintain cake volume (Kulp et al 1972; Huang et al 1982a,b; Telloke 1985). Kulp et al (1972) reported that the rate of initial rise in paste consistency of flours increased with chlorination and that hydration capacities were also consistently increased. They suggested that possibly the surface of starch granule was “activated” by the action of chlorine, which facilitated formation of starch-lipid or starch-protein complexes, resulting in stabilization of the cake batter during baking. Although chlorination did not alter the DSC-measured starch gelatinization phase transition, at 90°C, starch granules in batter containing chlorinated flour exhibited a greater loss of birefringence and swelled more than did starch granules in batters made with untreated flours (Huang et al 1982b). For measuring starch pasting characteristics, a Rapid Visco-Analyser (RVA) or Brabender Viscograph is commonly used for starch or flour slurries in water. However, cake batter is a high sugar system and measuring starch pasting behavior at high sugar concentration will be beneficial to explore cake baking functionality. To understand the mechanism of cake baking, changes in cake height during baking have been observed using time-lapse photography (Miller et al 1967; Yamazaki and Lord 1971; Kissell and Yamazaki 1979). In the present study, the effects of extent of chlorination, milling extraction rate, and particle-size reduction of flour on cake baking functionality were explored using RVA and time-lapse photography. MATERIALS AND METHODS Materials Straight-grade flour (SG, 74% milling yield) and low-extraction flour (Low X, 55% milling yield) samples from Croplan 594W wheat (soft red winter wheat grown in Ohio in 2004) were prepared according to the methods of Kweon et al (2009a). The wheat was cleaned, tempered to 14% moisture content, and milled with a Miag Multomat mill. Parts of the Low X flour sample were further processed to reduce particle size using an Alpine Kolloplex model 160-Z pin mill at 10,250 rpm, and the pin-milled flour was referred to as postmilled flour. For preparing chlorinated SG, Low X, and postmilled flours, ≈1 lb of each flour sample was treated with chlorine gas to produce specific target pH levels (5.2, 4.9, 4.6, 4.3, 4.0, and 3.7) (Mennel Milling, Roanoke, VA). For RVA analyses, reagent-grade sucrose was used. For cake baking, a partially hydrogenated, all-vegetable shortening (Smuckers, Orville, OH) and fine-granulated sucrose (Domino) were used. 1 USDA, ARS, Soft Wheat Quality Laboratory, Wooster, OH 44691. 2 Corresponding author. E-mail: [email protected] 3 Food Polymer Science Consultancy, Morris Plains, NJ 07950. doi:10.1094 / CCHEM-03-10-0046 This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. AACC International, Inc., 2010.