High water content, maltose and sodium dodecyl sulfate were effective in preventing the long-term retrogradation of glutinous rice grains - A comparative study

Prevention or inhibition of starch retrogradation is of special interest to food scientists and raises a challenge to the food industry. In this study, the effectiveness of different water contents and incorporation of eighteen food additives to inhibit retrogradation of whole glutinous rice grains was investigated. The retrogradation properties of pre-cooked glutinous rice gels were analyzed using texture profile analysis (TPA) and differential scanning calorimetry (DSC). At a water level of 74.8%, control sample (consisted of water and glutinous rice only) showed typical staling behaviors including a significant increase of hardness (from 1082 g to 2320 g), loss of adhesiveness (from -116 g.sec to -13 g.sec) and a value of retrogradation enthalpy (-4.4 J/g) after 4 degrees C storage of 14 days. Negligible retrogradation properties were observed if water content was above 80%. The addition of hydrocolloids, which showed good retrogradation preventing functions of starch in previous studies, could not prevent the retrogradation of glutinous rice grains. Whereas the addition of 11% of sugar (sucrose, maltose), 1.0% of NaCl, 2.4% of lipids and 0.24%-0.6% of surfactant (sodium dodecyl sulfate, monoglycerides, sucrose esters) reduced the increment of hardness value, and maintained the adhesiveness values after storage. The results with maltose and sodium dodecyl sulfate addition proved that they were two most effective additives in preventing staling behaviors and extending the shelf life (up to 14 days) of glutinous rice products.