Variation and Abundance of Resistant Starch in Selected Banana Cultivars in Uganda

Abstract

The physiochemical, structural, and molecular characteristics of starch influence its functional properties, thereby dictating its utilization. The study aimed to profile the properties and quantity of resistant starch (RS) from 15 different banana varieties, extracted using a combination of alkaline and enzyme treatments. Granular structure and molecular organization were analyzed using light microscopy, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The physiochemical and functional properties were also investigated. RS content ranged from 49% to 80% without significant relationship to amylose (AM) (r = -0.1062). SEM revealed significant microarchitectural differences on the granules potentially affecting granule digestibility. FTIR and chemometrics identified differences in the crystalline peaks, yielding varying degrees of the molecular order of the RS polymers that aid in differentiating the RS sources. Despite similar solubility and swelling profiles, the pasting profiles varied across varieties, indicating high paste stability in hydrothermal processing. Clarity ranged from 43% to 93%, attributed to amylose leaching. This study highlights that RS from bananas varies in quantity, structure, and functionality, necessitating individualized approaches for processing and utilization.

Keywords: banana; chemometrics; crystalline; microarchitecture; nutraceutical; resistant starch.

Figure 1

(a): Micrograph and granule distribution of granules in the analyszd banana varieties. A—cv Kibuzi, B—cv Mpologoma, C—cv Nakitembe, D—cv Nfuuka, E—cv Mbidde, F—FHIA17, G—KABANA6H, H—NAROBAN5. (b): Micrograph and granule distribution of granules in the analyzed banana varieties. I—NARITA21, J—NARITA23, K—cv Bogoya, L—cv Ndiizi, M—cv Gonja, N—cv Kivuvu, O—cv Kayinja.

Figure 1

(a): Micrograph and granule distribution of granules in the analyszd banana varieties. A—cv Kibuzi, B—cv Mpologoma, C—cv Nakitembe, D—cv Nfuuka, E—cv Mbidde, F—FHIA17, G—KABANA6H, H—NAROBAN5. (b): Micrograph and granule distribution of granules in the analyzed banana varieties. I—NARITA21, J—NARITA23, K—cv Bogoya, L—cv Ndiizi, M—cv Gonja, N—cv Kivuvu, O—cv Kayinja.

Figure 2

SEM imaging showing granule shape and size at EHT = 10 kv and WD = 9.2 mm, Scale bar: 10 µm (A). The high-magnification imaging from the red insets shows the micro-architecture of the granules (B). 1 depicts smooth granules of cv Nfuuka; 2 shows the layer expositions at the apex of cv Gonja, scale bar: 2 µm; 3 shows the folds of peaks and troughs in NARITA21; and 4 shows the grooves and pits in KABANA6H, scale bar: 500 nm.

Figure 3

Viscosity profiles for resistant starch from banana varieties: (A) Dessert, (B) Cooking-EAHB, (C) Hybrids, and (D) Plantain.

Figure 4

Swelling profiles (A) and solubility profiles (B) of 1% (w/v) starch suspension at 50–90 °C, showing 1—Cooking-EAHB, 2—Hybrids, 3—Plantain, 4—Dessert banana varieties.

Figure 5

FTIR spectra of the RS samples from banana analyzed in the range of 4500–500 cm⁻¹. Inset: absorption peaks used to determine the degree of crystallinity.

Figure 6

Biplot of the principal component analysis PC1 vs. PC2, describing the scores and variation in the crystallinity of the samples analyzed, showing scores represented by 95% confidence ellipses. MP—Mpologoma, MB—Mbiide, NK—Nakitembe, NF—Nfuuka, KB—Kibuzi, KY—Kayinja, KV—Kivuvu, GJ—Gonja, SN—Sukali Ndiizi, GM—Gros Michel, M30—NAROBAN5, M9—KABANA6H, N21—NARITA21, N23—NARITA23, F17—FHIA17. A—Samples display the A polymorph, B—samples display the B polymorph, and C—samples display a mixture of A and B, as described by the Pozo study [32].

Figure 7

Heat-map displaying the extent and direction of correlations (r) between RS compositional characteristics and physiochemical properties. Correlations were statistically significant at r ≥ 0.49 and r ≤ −0.49. C—clarity/%transmittance, RS—resistant starch content (g/100 g), AM—Amylose content (%), S—solubility at gelatinization (%), Tg—Gelatinization temperature (°C), GS—median granule size (µm), SP—swelling power (%), PV—peak viscosity (cP), PT—pasting time (min).