Aplicación de la fermentación láctica como estrategia de transformación y valoración de matrices vegetales

Abstract

In Colombia, strategies are being promoted to increase fruit and vegetable production, in order to take advantage of agricultural potential. However, there are also high food losses, low consumption and low transformation. Due to the above, the general objective of this thesis was the establishment of process conditions that allow the value generation on fruits and vegetables through lactic fermentation. Eight fruits and five vegetables were selected according to production, merchandising and consumption criteria. Mixes were obtained from combination of a fruit and a vegetable pulps. Based on their physicochemical characterization and viability of lactic bacteria, three mixtures were selected: yellow mix (mango 80% w/w, pumpkin 20% w/w), red (guava 40% w/w, red beet 60% w/w) and green (feijoa 40% w/w, spinach 60% w/w). The effect of two preliminary operations (neutralization and culture conditioning) on the fermentation, was evaluated. In neutralization case, a significant colour change was found, without bacteria growth. The culture conditioning was carried out in water, soy or oat drink; however, the bacteria growth was similar to that obtained without previous process. Afterwards, lactic fermentation of mixtures was evaluated. In red and yellow mixtures occurred lactic bacteria growth (from 104 to 106 CFU/g in red mix and from 103 to 107 CFU/g in yellow one), with a titratable acidity increase and pH decrease, while soluble solids remained stable. Lactic bacteria inoculated in green mix did not survive. Results in red and yellow mixes were similar with different co-cultures strains com position, in green mix bacteria maintenance was observed. The mixes were sensory analysed before and after fermentation, finding yellow mixture was the most accepted by consumers, then green and finally red one. A significant difference will not be detected when using different cultures. The effect of fermentation on organoleptic properties of yellow mix was evaluated, finding the main difference in acid taste. Microbial growth modeling in yellow mix was performed, finding the best adjustments using logistic equation and Monod models (R2 = 0.95) in comparison with Gompertz (R2 = 0.84). Carbohydrate monitoring on yellow mix did not show significant differences in sucrose, glucose or fructose during fermentation. However, there was an increase in lactic acid. Neither were significant differences on the antiradical activity during fermentation. Finally, shelf life study was carried out by monitoring the physicochemical, microbiological, bioactive and sensory properties of fermented yellow mix and stored at different temperatures (5, 15 and 25ºC). It was found that quality indicator is determinate by molds and yeasts growth. Using Arrhenius equation was obtained a model that allows to predict shelf life of fermented mix based on storage temperature. Confirm that fermented yellow mix and stored at the same temperature (5 º C), retains its quality for longer time (46 days) compared to unfermented mixture (12 days). It was concluded that, the designed process allows preservation of product, without altering antiradical capacity of fresh fruit and vegetables, adds functional properties and can be easily implemented by people in the field of Colombian agriculture.

Con el fin de aprovechar el potencial agrícola, en Colombia vienen impulsándose estrategias para incrementar la producción hortofrutícola y reducir las pérdidas de alimentos ocasionadas por el bajo consumo y la poca trasformación. El objetivo general de esta tesis fue el establecimiento de las condiciones de proceso que permitan la generación de valor en frutas y hortalizas, mediante la aplicación de la fermentación láctica. Para ello, se seleccionaron frutas, hortalizas y mezclas de éstas, considerando criterios como producción, comercialización, aceptabilidad y viabilidad de bacterias lácticas. Posteriormente, se evaluó la influencia de la neutralización y del acondicionamiento de cultivo, sobre el crecimiento de las bacterias lácticas, encontrándose que su efecto no es significativo. El estudio de la fermentación láctica de mezclas permitió obtener productos con una buena aceptabilidad y alta concentración de probióticos (1x108 UFC/g). Finalmente, el estudio de vida útil confirmó que la mezcla amarilla (mango 80% p/p y ahuyama 20% p/p) fermentada y almacenada a la misma temperatura (5°C), conserva su calidad por más tiempo (46 días) frente a la mezcla sin fermentar (12 días). Se concluyó que, el proceso diseñado permite la conservación del producto, sin alterar la capacidad antirradicalaria propia de la fruta y hortalizas frescas, le agrega propiedades funcionales y puede implementarse fácilmente por los campesinos productores en el ámbito del agro colombiano.