Physicochemical and Rheological Characterization of Roll‐in Shortenings

Abstract

AbstractThe composition and physical properties of roll‐in shortenings, commonly rich in trans and saturated fatty acids, were investigated and compared to other specialty fats, to provide insights into the physico‐chemical origins of their functionality. Triacylglycerols and fatty acid composition, polymorphic and melting behavior, solid fat content and large deformation rheological properties were determined. Roll‐in shortenings contained higher amounts of trisaturated and unsaturated triacylglycerols (12–27 %; 47–62 %) than other shortenings (9–11 %; 6–44 %). However, all exhibited high levels of saturates and trans fatty acids and similar crystal characteristics: β′ or mixed β′ and β, irrespective of their end use. Roll‐in shortenings had comparable melting peaks (42–52 °C) but sharper melting endotherms with higher enthalpies (38.6–43.3 J/g) than other bakery fats (18.7–25.4 J/g). This was in accordance with their well‐defined short spacings, indicative of smaller crystallites with more‐ordered packing. Solid fat profiles of roll‐in shortenings were akin to all purpose and cake interesterified shortenings, but not to all‐purpose and icing shortenings which displayed substantial melting as temperature rises. Differences in large deformation rheology (yield stress: σ*, apparent Young modulus: Eapp, yield value: C) were marginal and inconsistent with their solid fat content. Roll‐in shortenings exhibited Eapp, σ and C in the order of 1–2 × 106, 4–7 × 104, and 7–29 × 104 Pa, respectively. Particularly, the σ*and C, previously established as major parameters to specify the functionality of roll‐in shortenings, were not significantly different (p > 0.05). Overall, roll‐in shortening differed from other samples in regard to molecular makeup but not greatly in their physical parameters, suggesting that triacylglycerol composition has important implications on their functionality.