Evaluation of Shearing Rolls for Hulling Confectionary Sunflower Seed for Precision Planting

Abstract

<abstract> <bold><sc>Abstract. </sc></bold>The planting of sunflower seed has always used intact inshell seed. However, consumer demand for extra-large (XL) confection sunflower seed has led to new hybrid varieties, and much of the seed is now too large for current planting technologies and has poor germination. One alternative may be to use hulled kernels. Unfortunately, the impact hullers used in the snack food industry cause very high kernel breakage and poor germination. Thus, the effectiveness of shearing rolls was evaluated across several process conditions including: seed moisture content (6.1%, 7.8%, and 8.5%), differential roller speed (1.29, 1.55, and 1.68), roller gap distance (0.14 and 0.21 cm), and number of roller passes. Overall hulling effectiveness increased with decreased seed moisture content, and increased roller speed. At 6.1% moisture content, 0.21 cm roller gap distance, and 1.29 roller speed, proportion of dehulled seed increased by 54%, but the fraction of intact seed decreased by 19% when number of passes increased from 1 to 5. Although intact kernel yield improved with increasing pass number, germination and vigor index declined when the number of passes exceeded five, regardless of seed moisture and roller speed. The highest intact kernel yield of 68% with 88% germination and overall hulling efficiency of 4.9 was obtained using 7 passes, seed moisture content of 6.1%, and differential speed of 1.68. The results suggest shearing rolls provide a vast improvement of intact kernel yield and germination when compared to impact hulling used in the industry.