Characterization of amino acids and oligosaccharides in whole sugarcane culm flour: a potential food ingredient

Sugarcane bagasse has been investigated as a potential source of prebiotic oligosaccharides. However, the use of sugarcane as a food ingredient remains underexplored, particularly regarding the integral utilization of its stalks. In recent years, our research group has been exploring the development of whole sugarcane stalk flour as an innovative strategy to promote integral utilization of this crop, minimize biomass waste and obtain value-added food ingredients. Owing to its natural sugars, the flour may partially or totally replace sugar in food formulations, while its fibrous components may influence the glycemic response of the final product. Despite its promising nutritional and technological characteristics, information regarding the amino acid and oligosaccharide composition of whole sugarcane stalk flour remains limited. This study aimed to characterize the amino acid and oligosaccharide profiles of whole sugarcane stalk flour obtained from three sugarcane varieties (RB966928, RB925345, and RB867515), which were selected because they are among the most widely produce in Brazil. The obtain the flour, whole stalks were sanitized, sliced, oven-dried with forced air circulation, ground in a knifer mill, and sieved to a particle size of approximately 0.3 mm (48 mesh). The amino acids and were oligosaccharide determined by HPLC-DAD. Amino acids contents ranged from 4.29 to 35.36 mg 100 g^-1, and the profile varied among varieties. Phenylalanine (27.56 – 35.36 mg 100 g^-1) and serine (24.94 – 31.52 mg 100 g^-1) were the most abundant, while glutamic acid showed the greatest variation (7.89 – 26.41 mg 100 g^-1) (p < 0.05). Essential amino acids (valine, methionine, phenylalanine, and lysine) were detected, but lysine was found only in RB925345 and RB867515. Although these values do not qualify the flour as a significant protein source, the varietal profile may contribute to color and aroma development during thermal processing. Regarding oligosaccharides, inulin was the predominant compound, (4.91 – 8.32 g 100 g^-1), with RB925345 showing the highest content (p < 0.05). Kestose was detected in RB966928 and RB925345 (2.02 and 2.27 g 100 g^-1, respectively), whereas nystose was found only in RB925345 at low levels. RB867515 contained no fructooligosaccharides other than inulin but presented the highest xylohexaose content (2.83 g 100 g^-1). The inulin contents are within the range reported for foods such as anion, asparagus, and leek, whereas kestose in generally found at low levels in natural sources. The identification of these compounds is relevant because inulin-type fructans and kestose are recognized bifidogenic substrates, and xylo-oligosaccharides, such as xylohexaose, also exhibit prebiotic activity. The oligosaccharide profile indicates that the flours may be a promising matrix for further investigation of its prebiotic potential and its use as a food ingredient.