Original article Effect of annealing on the functionality of Bambara groundnut (Vigna subterranea) starch–palmitic acid complex Samson A. Oyeyinka, 1 * Rukayat Adegoke, 1 Adewumi T. Oyeyinka, 2 Khadijat O. Salami, 1 Omotola F. Olagunju, 4 Fausat L. Kolawole, 1 John K. Joseph 1 & Islamiyat F. Bolarinwa 3 1 Department of Home Economics and Food Science, University of Ilorin, Ilorin, Nigeria 2 Department of Food Science and Technology, Kwara State University, Malete, Nigeria 3 Department of Food Science and Engineering, Ladoke Akintola University of Technology, Ogbomoso, Nigeria 4 Department of Food and Nutrition, Afe Babalola University, Ado Ekiti, Nigeria (Received 20 July 2017; Accepted in revised form 5 September 2017) Summary Bambara groundnut is an underutilised African leguminous crop. This study investigated the effect of annealing on the complexing ability and functionality of Bambara groundnut starch with palmitic acid. Corn starch was included as the reference. Annealing created cracks and pores on the surface of Bambara groundnut and corn starches, respectively. Bambara groundnut starch had significantly higher amylose content, higher peak and final viscosities than corn starch. The peak viscosities of native Bambara groundnut and corn starches significantly reduced with palmitic acid addition. Greater reduction in peak viscosities was observed when the annealed starches were complexed with palmitic acid, suggesting that more palmitic acid was complexed after annealing. This was confirmed by XRD peaks and melting enthalpies. Pasting of native Bambara groundnut and corn starches with palmitic acid resulted in the for- mation of type I V-amylose complexes, while type II complexes were formed from annealed starches pasted with palmitic acid. Keywords Annealing, Bambara groundnut, corn, functionality, palmitic acid, starch. Introduction Starches in the native form are generally unsuitable for industrial applications. They are usually modified to improve functionality and application. Currently, starches from corn, potato and tapioca dominate the category of starch used in the industry. The physico- chemical properties of these starches have been widely researched. However, due to the pressure on some starch sources, for example corn for uses other than starch, there is a growing demand for alternative starch sources. Furthermore, many underutilised legu- minous crops such as pea (Pea sativum) and Bambara groundnut (Vigna subterranea) are now being proposed as possible starch source for the industry. Bambara groundnut is reportedly rich in starch (18–45%) (Afolabi, 2012; Oyeyinka et al., 2015, 2016a). Hence, this crop has potential as an alternative starch source to commercial starch sources. Previous research modified Bambara groundnut starch (BGS) using annealing (Adebowale & Lawal, 2002), oxidation, acetylation (Adebowale et al., 2002), carboxymethylation (Afolabi, 2012) or lipids (Oyeyinka et al., 2016b,c,d). Adebowale & Lawal (2002) found that ANN caused significant reduction in swelling power and peak viscosity of BGS. Other reports on BGS modification found that lipids can improve its thermal stability (Oyeyinka et al., 2016b,c,d) and reduce its tendencies towards retrogradation (Oyeyinka et al., 2016c). BGS pasted with stearic acid caused sig- nificant reduction in peak viscosity, which was associ- ated with the formation of amylose–lipid complex (Oyeyinka et al., 2016c). Several researchers are currently focusing on improving the degree of complexation of starch with lipids, either by increasing the incubation time of starch with lipids (Chang et al., 2014), using high pres- sure homogenisation (Oyeyinka et al., 2016b,d) or extending the pasting time of starch with lipids (D’Silva et al., 2011). Nakazawa & Wang (2004) stud- ied the effect of annealing on starch–palmitic acid interaction. According to these authors, more palmitic *Correspondent: Emails: sartf2001@yahoo.com, oyeyinka.sa@unilorin.edu.ng International Journal of Food Science and Technology 2017 doi:10.1111/ijfs.13635 © 2017 Institute of Food Science and Technology 1