Utilization of Cracked & Broken Bean Flour in Omega 3 Fortified Extruded Snacks
March 07, 2008
Mehmet Tulbek, Clifford Hall, Brian Sorenson, Northern Crops Institute at North Dakota State University Fargo, ND, Department of Cereal and Food Sciences North Dakota State University Fargo, NDNavy and pinto beans were milled with Fitzmill Model DAS-06 (Fitzpatrick Company, Elmhurst IL) (Pictures 1-2). Mill speed was conducted at 2400, 3600 and 7200 RPM and screw speed was arranged as 15 RPM. Screen size was used as 0.0109. Particle size distribution and detailed data was given in Table 1-3. Results indicated similar results in terms of milling quality. As the mill speed increased particle size decreased. Cracked and broken beans had the lowest particle size compared to navy and pinto beans
Extrusion is a unique process which helps utilize edible beans by inactivating enzymes, antinutritional factors and enhancing taste attributes. Due to the diversity and changes in the US agriculture, food companies are looking for alternative and feasible ingredients for snack food manufacturing. Edible beans are good source of protein and fiber and can be successfully utilized in developing health based extruded snacks fortified with cold milled flaxseed, which is a major source omega-3 fatty acids. In this project we focused on utilizing broken and cracked beans in snack food manufacturing.
The objectives of this project were i) to develop a milling process for cracked and broken edible beans and also whole beans; ii) to assess the shelf life properties of cracked and broken bean flour; iii) to develop a method for producing extruded snack products from omega-3 fortified dry bean flour.
Navy, pinto and cracked mixed bean flours did not show significant differences in terms of shelf life stability. However bean flour quality significantly improved with cooking application. Hydrothermal treatment prior to milling significantly improved cracked bean flour quality. Gas chromatography tests indicated higher levels of hexanal aldehyde during 8-week storage in non treated bean flour samples, compared to cooked flours. Storage stability was related to hydrothermal treatment which is possibly related to the enzyme activity of bean flours.
Extrusion was conducted according to standard corn curl processing method of Wenger (Picture 3). Screw speed and water absorption levels were adjusted at 350 RPM and 0.328 kg/min respectively. Bean samples milled at 7200 RPM were utilized in extruded snack process.
Specific mechanical energy values decreased as the cold milled flaxseed addition increased during extrusion as observed in the previous study. Snack quality analyses indicated that water activity scores increased with navy and cracked bean flour, whereas no change was observed with pinto bean flour. Milled flaxseed addition significantly (P<0.05) increased the oil content of the samples. In terms of 20% milled flaxseed fortified extruded snacks, navy bean and cracked mixed bean flour samples had higher oil content (6.8 and 6.2% respectively) compared to pinto bean flour (5.6%). Alpha linolenic acid was found to be the major fatty acid (51-53%) followed by linoleic acid (20-22%) in the oil fraction. Shelf life stability of extruded bean snacks was evaluated by headspace volatile analysis. Gas chromatography was conducted and secondary metabolites of lipid oxidation were analyzed. Propanal the primary aldehyde of alpha-linolenic acid was detected in all extruded bean snack samples at 4-month storage. As the milled flaxseed addition increased, propanal content increased. Due to the high temperature and shear during extrusion, cracked bean flour had results similar to navy and pinto beans in terms of product quality. In conclusion cracked and broken beans could be introduced as an alternative ingredient with high temperature high shear food process applications. The results of this project will be further discussed and presented during the Pulse Quality and Utilization Short Course which will be organized by Northern Crops Institute on August 5-7, 2008 at Fargo, ND.
Picture 3. Wenger TX-52 Twin Screw Extruder
Table 1. Milling conditions and particle siza alalysis of navy beans
Table 2. Milling conditions and particle size analysis of pinto beans
Table 3. Milling conditions and particle size analysis of cracked beans