CARACTERIZACIÓN DE LA CINÉTICA DE CRECIMIENTO DE MICROORGANISMOS LÁCTICOS A TRAVÉS DE ULTRASONIDOS Y SU TRANSFORMADA WAVELET

Abstract

During milk fermentation, composition of growth medium changes due to development, growth and multiplication of lactic acid bacteria which consume lactose, amino acids and other nutritional requirements. In return, these bacteria produce lactic acid, acetaldehyde, exopolysaccharides and other metabolites which originate changes in the physicochemical parameters of the medium such as pH, viscosity, acidity, among others. These changes affect the wave propagation velocity and acoustic impedance of the milk. To control the fermentation process whose end product is a food, appropriate variables are required from the viewpoint of food handling. Monitoring that do not require contact with the product and do not alter its properties is desirable. The low-power ultrasonic signals have this advantage and have been applied in the study of biological processes. In this thesis, kinetics of fermentation of Lactobacillus acidophilus, Streptococcus thermophilus, and the mixture of both are studied through the pH, UFC and ultrasound propagation. Ultrasonic signals applied are processed by means of the Fourier and wavelet transform. It is concluded that identification of the kinetics of fermentation of the bacteria studied through the changes in the ultrasonic wave attenuation is possible, but is not possible to identify bacteria in the mixture case.