Shelf‐life prediction of milk‐millet powders

Abstract

AbstractMigration of moisture and oxygen into packages during storage lead to deteriorative reactions such as nonenzymatic browning (NEB), stickiness, caking, and oxidation. Actual shelf‐life testing of milk‐millet powders is tedious and time‐consuming as they have long storage stability. The aim of this study was to predict the shelf‐life of spray‐dried milk‐millet powders based on deteriorative reactions due to moisture and oxygen uptake, and evaluate whether the prediction models could be applied as an alternative to accelerated or normal shelf‐life testing. Fresh cow milk was standardized, concentrated to 22% total solids (TS), blended with millet wort of 22% TS in 1:1 ratio, and dried into powder using a lab‐scale co‐current type spray dryer. The predicted shelf‐life of milk‐malted foxtail millet powder based on stickiness and NEB caused by moisture gain was 17 and 30 days in high‐density polyethylene (HDPE), 41 and 58 days in EVOH laminate (LDPE/EVOH/LDPE), and 96 and 134 days in polyethylene‐terephthalate (PET) laminate (PET/Al foil/PET/LDPE) pouches, respectively. The corresponding shelf‐life of milk‐barnyard millet powder based on stickiness and NEB was 18 and 30 days, 66 and 96 days, and 90 and 102 days, in HDPE, EVOH laminate, and PET laminate, respectively. Similarly, the predicted oxygen limiting shelf‐life based on thiobarbituric acid reactive substances was found to be 40, 75, and 86 days for milk‐foxtail millet powder and 32, 72, and 93 days for milk‐barnyard millet powder in HDPE, EVOH laminate, and PET laminate, respectively. The rate of deteriorative reactions was the lowest in PET laminate pouches because of its excellent barrier properties over that of HDPE and EVOH even at the adverse accelerated storage conditions. The simulation model was adequate and reliable in predicting the shelf‐life of milk‐millet powders in packaging materials with wide range of barrier properties.Practical ApplicationsDeteriorative reactions such as caking and nonenzymatic browning induced by moisture, and oxidative reactions induced by ingress of oxygen into the package, affect the shelf‐life of milk‐millet powders. For such food powders having long shelf‐life, regular and accelerated shelf‐life testing are cumbersome and sometimes untenable. Simulation and mathematical modeling of shelf‐life is an alternative to long‐term shelf‐life tests. In this study, models for predicting the shelf‐life of milk‐millet powders based on moisture gain and oxygen uptake were developed. Prediction of shelf‐life will be helpful to monitor the product stability against spoilage by deteriorative reactions. The models could also be used for evaluation of shelf‐life of millet‐ and other food powders in flexible packaging materials. The prediction model not only required less time and resources but also was adequately reliable.