Nutritional and Sensory Properties of Protein Enriched Bread
Bread is one of the most consumed foods worldwide. It is high in carbohydrate and low in protein content. Nowadays, an increasing number of people prefer healthier food with balanced nutrients. Red meat is known to possess high quantity of complete protein and also rich in micronutrients. Navy bean is rich in fibre and plant protein as well, and it is also a low glycaemic index food. In the present study, I seek to develop a new bread product with rich protein content from red meat and fibre-rich navy bean to improve the nutritional values. The objectives of this research were to investigate physicochemical, sensory attributes and digestibility of wheat bread substituted with red meat and navy bean at different levels. The hypothesis of this study was that the fortification of bread with red meat and navy bean will improve the nutritional values of bread with improved physicochemical, sensory and digestibility. In my study, bread formulations with 25% and 50% of raw beef by weight (containing 66g and 132g meat slurry, respectively), navy bean powder (15% and 30%), and mixed meat slurry and navy bean powder (10M30NB , 18M15NB, 20M30NB and 35M15NB) were developed. All samples were then evaluated for their physical, nutritional and sensory attributes. In addition, static in vitro digestion model was used to analyse the effects of the new ingredients on the digestibility of the enriched bread. In vivo the glycaemic index of bread samples was measured in healthy subjects.
All of the fortified bread samples, except 15NB and 30NB, showed significant increase (p < 0.05) in protein content, whereas carbohydrate content was found to decrease significantly (p < 0.05) in all bread samples. Substitution of wheat flour with meat and navy bean resulted in significantly lower (p < 0.05) loaf volume with an increased loaf weight as compared to the control. Fortified breads were noted to significantly decrease (p < 0.05) in the lightness and increase redness (red meat) and yellowness according to the L*, a*, b* colour system. Texture results showed that the 25M, 50M and 35M15NB breads were significantly increased (p < 0.05) in hardness as compared to the control. Scanning electron microscopy (SEM) pictures of control bread had more randomly distributed gluten matrix as compared to the fortified breads, which had less starch granules embedded into larger protein matrix. Sensory evaluation showed that 15NB bread had the highest score for overall liking attribute. Addition of meat and navy bean contributed to increment the deficient essential amino acids in bread, such as lysine, threonine and leucine. Fortified breads showed relatively lower glycaemic index (GI) value in bread than the control.
Overall, the results showed that the incorporation of meat and navy bean changed the nutritional and physicochemical properties and digestibility of bread and GI values as well. The outcome of the present study will have greater impact on extending the use of meat to develop healthier food products and aligns with the AgResearch programme “Red Meat Combifoods: End-to-end management of protein nutrition” supported by the Crown Research Institute Core Fund of AgResearch Ltd.