Characterization of Fructan Content from Stem Juices of Different Varieties of Agave Atrovirens, Traditionally Used for the Production of Pulque. Production of a Sweetening Syrup by Chemical and Enzymatic Processing

Abstract

Agave atrovirens, the hardiest species of Agave in Mexico, thrives in tough, infertile soils and extreme temperatures across a wide range of altitudes, particularly in impoverished rural areas of Central and Northern Mexico. Its potential for agroindustrial use could offer a pathway to social and economic prosperity for many communities. Traditionally, A. atrovirens is tapped for its sap, known as aguamiel, which is harvested from the leaves and collected in a cavity, carved into the central stem. This sugar-rich sap serves as the raw material for pulque, an ancient indigenous fermented beverage. However, pulque is unstable with a short shelf life and limited market reach. Despite A. atrovirens stems having lower sugar content compared to other species, its high inulin content and large biomass yield, make it a valuable raw material. One potential strategy for A. atrovirens is its use in liquid sweeteners. While juices rich in fructans from A. tequilana and A. angustifolia are currently employed in the production of industrial fructans, distilled beverages, and sweeteners, A. atrovirens remains relatively underexplored. The total soluble carbohydrate content in Agave juices was, on average, 154.3 g/L. Carbohydrate composition of raw Agave juices (Before Hydrolysis): high molecular fructans 130.0 g/L; sucrose 10.4 g/L, glucose 7.0 g/L and fructose 6.4 g/L). This study aims to characterize stem extracts from three varieties of A. atrovirens (Blanco, Cosmimaco, and Xaco), shedding light on its sugar content, juice composition, and the hydrolytic conversion rate of native fructans, by either acid or enzymatic treatment. Experimental results indicate significant differences among the varieties in terms of sugar content and composition Raw stem juices from A. atrovirens have a higher concentration of sucrose than glucose or fructose, with the majority being polymerized fructans. Hydrolyzed juices of all three varieties show a higher concentration of fructose (8.65-19.52% w/w); a lower glucose content (4.85-9.68% w/w) and a very low sucrose content (0.13-0.77% w/w). A prototype sweetening syrup derived from enzymatic hydrolysis of mixed fructans from A. atrovirens contained (w/v): 48.56% reducing sugars; 29.5% fructose; and 10.8% glucose. As well as 8% w/v fructo-oligosaccharides.