Formation and Characterization of Amylose–Lipid Complexes in Green Banana (Musa paradisiaca suaveolens Blanco) Flour Enriched with hot-pressed and cold-pressed Virgin Coconut Oil

This study explores the formation of amylose–lipid complexes in green banana flour derived from the Bungulan variety (Musa paradisiaca suaveolens Blanco), enriched with virgin coconut oil (VCO), as a strategy to reduce starch digestibility and lower the glycemic index. The native banana flour was first characterized by its apparent amylose content (AAC), determined to be 19.05 ± 0.82%, confirming its suitability for amylose–lipid complex formation. Two types of VCO—hot-pressed and cold-pressed—were subjected to fatty acid methyl ester (FAME) derivatization and subsequently analyzed via gas chromatography-mass spectrometry (GC-MS). The major FAME components identified included lauric acid (C12:0, 39.16%), myristic acid (C14:0, 20.69%), palmitic acid (C16:0, 12.32%), oleic acid (C18:1, 8.72%), caprylic acid (C8:0, 6.94%), capric acid (C10:0, 6.41%), and stearic acid (C18:0, 4.65%), alongside several minor fatty acids. Hot-pressed and cold-pressed VCO were incorporated into the flour under controlled conditions to optimize complex formation. Fourier-transform infrared (FTIR) spectroscopy confirmed the formation of amylose–lipid complexes through characteristic absorption bands corresponding to O–H stretching (~3450 cm⁻¹), C–H stretching (~2950 cm⁻¹), C=O stretching (~1750 cm⁻¹), and C–O stretching (~1000 cm⁻¹). Differential scanning calorimetry (DSC) further validated complex formation, showing melting transitions at ~24–26 °C, attributed to unbound coconut oil, and distinct endothermic peaks at ~90–105 °C, indicative of thermally stable V-type amylose–lipid complexes. In vitro enzymatic digestion at 37 °C revealed reduced starch hydrolysis in all oil-complexed samples compared to native banana flour. Kinetic modeling based on fitted C∞ values—representing the equilibrium concentration of maltose release per gram of starch—demonstrated a progressive decline in digestibility: the native flour had a C∞ of 36.85 mg/g (3.50% starch hydrolysis). In comparison, cold-pressed and hot-pressed VCO treatments yielded slightly lower values of 35.80 mg/g (3.40%) and 35.30 mg/g (3.35%), respectively. These reductions suggest enhanced resistance to α-amylase digestion due to the formation of amylose–lipid complexes, which act as structural barriers and reduce enzymatic accessibility.