Effect of rum amount and functional ingredients on physical properties and microwaveable reheatability of rum cake

Abstract

Rum cake remains a popular consumer good in the United States and Caribbean islands. A single-serving, frozen rum cake that is ready-to-eat after 1 min of microwaving was developed, however microwaving of cereal-based goods often leads to textural problems. To minimize textural defects (tough, rubbery, and gummy) caused during microwaving, functional ingredients such as modified starches, emulsifiers, and hydrocolloids are commonly added to cakes. The two main objectives were: 1) to determine how rum amount affects texture and structure of fresh rum cake, and 2) to analyze two functional ingredients (modified starch and glycerol monostearate (GMS)) on final quality of fresh rum cake and frozen then microwave reheated rum cake. To determine the effect of rum, four rum cake formulations were analyzed (0% (control), 7.6%, 10.1%, 12.6% rum w/w, true %). Water was added as needed to formulations to obtain the same moisture level and all other ingredients and processes were held constant. For the functional ingredients experiment, three levels of modified starch (0.21%, 0.42%, 0.63% w/w, true %) and two levels of GMS (0.11% and 0.17% w/w, true %) were analyzed using a 2x3 factorial design. Control samples contained no modified starch or GMS. Specific gravity, consistency, and final temperature of the batters were measured along with final cake height to determine final cake volume. Physical properties of cakes were also analyzed through texture analysis (cake firmness and elasticity) using a TA-XT Plus Texture Analyzer. For the alcohol study, rum presence showed an increase in elasticity and cake height (p<0.05). The actual amount of rum (7.6, 10.1%, and 12.6%) was not significant, but each treatment that contained rum was significantly different from the control (0% rum). Rum presence of significantly reduced moisture loss of cakes (p<0.05), which could be a contributing factor to the increased elasticity and height of rum-containing formulas. The increase in elasticity and height are both seen as positive attributes from a consumer acceptance standpoint, as consumers are looking for high volume cakes that will not crumble under stress. These results suggest that the presence of rum in a cake creates a more elastic cake with greater volume and height, indicating a physiochemical effect of rum in the batter or through the prevention of moisture loss. In the functional ingredient experiment, the addition of a pregelatinized waxy maize starch increased the batter consistency (p<0.05). In fresh cakes, the addition of starch and GMS at low levels resulted in decreased firmness. All three starch levels and both GMS levels tested significantly increased cake elasticity when compared to the control. For both firmness and elasticity, the presence of the ingredient was more impactful than percent added. Decreased firmness and increased elasticity are both seen as positive textural attributes by consumers. In frozen and then microwave reheated cakes, no significant differences were observed in peak firmness or height. Elasticity significantly decreased (p<0.05) when comparing control versus high starch cakes and control versus low GMS cakes. These results indicate that the modified starch and GMS used in this experiment did not have the expected positive impact on physical properties of frozen, microwave reheated rum cakes. Procedural changes to the length of frozen storage or reheating method may provide some additional learnings on the freeze-thaw effectiveness of these ingredients. Overall, the addition of rum to a cake batter creates an airier, more elastic cake, although the level of rum was insignificant. The addition of functional ingredients such as modified starch and GMS had a positive impact on physical properties of fresh cakes in the form of decreased firmness and increased elasticity, but this same impact was not observed in cakes that had been frozen and then microwave reheated.