Kinetics and microbiology of pulp silage from decorticated Agave salmiana leaves

Abstract

A new machine for decortication of residual leaves of Agave salmiana was developed, yielding, juice (43 ± 6 %), wet pulp (25 ± 3 %), and wet fiber (18 ± 4 %) with an overall 86 ± 2 % recovery. Production of lactic acid (LA) and acetic acid (AA) in micro silages of wet agave pulp were assessed together with the evolution of lactic acid bacteria (LAB) and mesophile bacteria (MB) populations. LA spontaneous fermentation was followed by a two stage first order kinetics model (R2 = 0.89), At the start (pH = 5) MB population was 100 times higher than LAB = 1xE8 CFU/g. Fermentation peak was reached at 11 days when pH = 4, LA = 119 g/kg, LAB = 4xE9 CFU/g, and MB = 1xE8 CFU/g showing that LAB overgrew MB. Average AA values were negligible during the first month. After two months, LA and AA titers were 80 and 40 g/kg, respectively. Pasteurized pulp with LAB < 1E2 CFU/kg showed, significant LAB growth after one week of silage (3xE7 CFU/g). Inoculation of pasteurized pulp by selected LAB strains produced lower counts (8xE9 CFU/g) as compared to spontaneous fermentations (9xE10 CFU/g). Hence, spontaneous agave pulp fermentation is a reliable process for conservation of agave pulp and seems worth scaling-up as the basis for ruminant production in the dry lands of Central Mexico. It remains to develop the utilization of the juice and fiber fractions of A. salmiana as the basis for new biochemical and textile industries.