ABSTRACT
In recent years, acidophilic, heat-resistant, and spore-forming spoilage bacteria have been identified in pasteurized or treated by high hydrostatic pressure (HPP) fruit juices. Alicyclobacillus acidoterrestris is the bacteria more frequently linked to the spoilage of this type of product because its spores can survive conventional pasteurization and HPP treatments. Under favourable conditions, such as an acidic pH, its spores can germinate and multiply, with the consequent production of guaiacol. Guaiacol is a compound with an undesirable odour ("medicinal", "smoked" or "antiseptic"). In this context, our objective was to determine the prevalence of A. acidoterrestris in 150 Spanish pasteurized and HPP-treated fruit juices purchased from supermarkets or received from manufacturers. Then, the isolates and the reference strain (CECT 7094 T) were characterized to establish differences in terms of (i) growth capacity at different pH and temperatures, and in (ii) guaiacol production capacity. The results showed a high incidence of A. acidoterrestris (18.0 %) in the analysed juices. The 44.4 % of the isolates came from blends of fruit juices. Within juice blends, 9 juices contained apple juice among their ingredients. This represents a 18.8 % of incidence with respect to the total of blended juices with apple. A high incidence in monovarietal apple juices was also observed (3 out of 14 samples). Regarding the characterization of the isolates, EC1 (isolated from an apple concentrate) showed the highest growth capacity at pH 4.0 at temperatures from 20 to 55 °C. Besides, three strains (R42, EC10, and EZ13, isolated from clementine, plum and white grape juice, respectively) could grow at room temperatures (20 and 25 °C). For pH, only EZ13, isolated from white grape juice, was able to grow significantly at pH 2.5. Finally, the production of guaiacol ranged from 74.1 to 145.6 ppm, being the isolate EC1 the one that produced more guaiacol after 24 h of incubation at 45 °C (145.6 ppm). As we have observed, there is a high incidence of A. acidoterrestris in marketed juices and intermediate products despite the treatments received (pasteurization or HPP). Under favourable conditions for the development of this microorganism, it could produce enough guaiacol to spoil the juices before their consumption. Therefore, in order to improve the quality of fruit juices it is necessary to investigate in more detail the origin of this microorganism and to find strategies to reduce its presence in final products.
Subject(s)
Alicyclobacillus , Malus , Fruit and Vegetable Juices/analysis , Hydrostatic Pressure , Fruit/microbiology , Malus/microbiology , Guaiacol/analysis , Spores, Bacterial , Beverages/microbiologyABSTRACT
In this work the effect of the presence of the melanoidins from glucose-asparagine on the enzymatic activity of trypsin is studied. It was observed that an excess of N alpha-benzoyl-L-arginine ethyl ester (BAEE) has an inhibiting effect on this enzyme activity. The maximum reaction rate was obtained for a 0.06 mN substrate concentration. It is also observed that the presence of melanoidin inhibits the enzymatic activity of trypsin. This inhibition can be described as a linear mixed type where the inhibition constant alpha K(i) of the substrate-inhibitor complex is higher than the inhibition constant K(i) of the complex enzyme-inhibitor with a alpha value of 1.88.
Subject(s)
Asparagine/chemistry , Glucose/chemistry , Polymers/toxicity , Trypsin/metabolism , Glutamic Acid/metabolism , Kinetics , Molecular WeightABSTRACT
En el período comprendido de abril a junio de 1990, se trataron 5 pacientes del sexo femenino con edad promedio de 47 años. Todos tenían historia de colecistectomía de 1 mes a 15 años. La sintomatología era de dolor abdominal e ictericia en 4 y solamente ictericia en 1. En 3 casos la litiasis era intrahepática y en 2 la litiasis era gigante y no se consideraron candidatas a tratamiento endoscópico. A todos los pacientes se les efectúo esfinterotomía y colocación de sonda nasobiliar. se procedió al tratamiento de litotricia extracorporea y posteriormente se dejaba solución salina en infusión por la sonda nasobiliar. En todos los pacientes excepto en uno, se solucionó el problema con una sola sesión. Se concluye que la colocación de una sonda nasobiliar para la instilación de solución salina como complemento al tratamiento de la litotricia extracorpórea de la litiasis de la vía biliar, evita la obstrucción de la vía biliar con los fragmentos que se formen, arrastra a los fragmentos hasta el duodeno y ayuda a la localización del cálculo durante el procedimiento
