Browsing by Author "Malaka, Ratmawati"
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Item Effect of lanthanide ions stress on lactic acid fermentation performance of Streptococcus thermophilus during milk processing(AIP Publishing, 2023-06-05) Vargas Vargas, Maynor Alberto; Jiménez Silva, Arlette; Hernández Chaverri, Rodolfo Antonio; Malaka, RatmawatiThe purpose of this research is to evaluate the inhibitory effect produced by the presence of lanthanide ions (Ln3+) at different concentrations on the biochemical process of lactic acid fermentation. Assays were carried out in reconstituted skim milk media with different contents of solids non-fat (SNF) by inoculation with Streptococcus thermophilus from commercially available freeze-dried, single-strain starter culture in Costa Rica, currently used in the manufacture of commercial cheese, yogurt, and other dairy products. Lanthanide elements find their main applications as structural components of electronic devices widely used in modern information and communication technologies (ICTs), among which cell phones, flat-screen televisions, hearing aids, desk computers, laptops, household appliances, and energy-saving fluorescent bulbs can be mentioned. In addition, they also play an important role in the manufacture of electric cars and wind turbines contributing to the development of alternative clean energies. Nevertheless, little progress has been made in developing recycling processes for the corresponding electronic waste containing these elements, which are being currently recognized as potential emerging pollutants in the environment. In this study, it was found significative inhibitory effects on the lactic acidification rate in the presence of lanthanides concentrations as low as 10-4 mol/L, at different incubation temperatures, incubation periods, and solid non-fat contents (SNF %), which might affect the quality and safety of some agro-industrial products of importance for the economy of the country, as well as some common biological processes such as the natural decomposition of organic matter and silage.Item EFFECTS OF BACTERIAL EXOPOLYSACCHARIDE ON RHEOLOGICAL PROPERTIES OF ACID MILK CURD AND ITS CORRELATES(AJFAND: African Journal of Food, Agriculture, Nutrition and Development, 2022-02-01) Malaka, Ratmawati; Baco, S; Jaya, AK; Vargas Vargas, Maynor AlbertoExopolysaccharide (EPS) is a general term for the forms of bacterial polysaccharides found outside the cell wall of bacteria. The industrial microbiologist has become interested in exploiting microbial exopolymer production due to an increasing interest and need for novel polysaccharides. The use of bacterial EPS in acid milk curd (AMC) production accounts for a quality improvement of the milk curd in terms of stability during the normal operations of storage and transportation. On the other hand, EPS have been used as prebiotic because of its health-promoting effects in human beings. The objective of this study was to evaluate the rheological properties (RP) and their statistical correlations in acid milk curd (AMC) samples added with bacterial EPS. Rheometric properties are suitable parameters to evaluate food quality such as AMC. Some of the RP normally used in this evaluation include elastic modulus (EM), hardness (HR), breaking energy (BE), viscosity (VIS) and stress. Correlation between pairs of these parameters are important to understand in order to predict statistically other parameters in case they cannot be easily determined. Acid milk curd samples were formulated using 10, 15, and 20 % of reconstituted skim milk (RSM), to which 0, 0.2, 0.4, 0.6, 0.8, and 1 % level of EPS were added, respectively. Samples were pasteurized at 60 o Cfor 30 min, and at 85 o Cfor 30s. Afterwards, AMC samples were tempered to 40 °Cinoculated with Lactobacillus delbrueckii subsp. bulgaricus B-5b, and incubated at 37 °C for 16 h. Results indicated that viscosity and hardness showed the strongest and highest correlation among all the parameters evaluated (r=0.9272) and it was comparable to that between viscosity and breaking energy (r=0.8349) and breaking energy and hardness (r=0.7694). However, elastic modulus and viscosity showed a rather low correlation (r=0.5394) and very low correlation (r=0.1830), respectively, suggesting that estimation of elastic modulus from viscosity values would be inaccurate. In general, rheometric properties of acid milk curd increased with higher EPS concentrations until 1 % level of EPS addition. Therefore, it is recommended to use BE and HR values, and BE and VIS values to predict accurate measurements of other RP values.Item Evaluación de la producción de exopolisacáridos de una cepa de Lactobacillus delbrueckii subsp. bulgaricus en diferentes sustratos(2020-01-05) Malaka, Ratmawati; Maruddin, Fatma; Dwyana, Zaraswati; Vargas Vargas, Maynor AlbertoEl objetivo de esta investigación fue determinar el medio óptimo para la producción de exopolisacáridos (EPS) por una cepa viscosa de Lactobacillus delbrueckii subsp. aislada de una muestra de leche fermentada comercial producida en Sulawesi, Indonesia, en leche descremada reconstituida (RSM) 10% (p / v), suero de leche (MW) y suero de leche de soja (SMW), bajo condiciones de crecimiento óptimas para esta cepa. El suero de leche se obtuvo coagulando leche fresca por medio de látex de papaya al 3% (v / v); el suero de leche de soya se obtuvo de la industria de tofu en Indonesia. Se determinó la composición química de los sustratos por análisis proximal y la esterilización se realizó en una autoclave a 121° C durante 15 min. Los medios de cultivo se inocularon con 1% (v / v) de un cultivo iniciador de Lactobacillus delbrueckii subsp. bulgaricus y luego se incubaron a 30°C durante 16 h. La producción de EPS, el contenido de ácido láctico, el recuento celular y el pH se determinaron después de enfriar los medios a 5° C. Los resultados mostraron que sobre la base de las características de crecimiento de L. delbrueckii subsp. bulgaricus, el mejor medio para la producción de EPS fue RSM al 10% (258,60 ± 26,86 mg / L) en comparación con el suero de leche (69,60 ± 9,48 mg / L) y el suero de leche de soya (49,80 ± 9,04 mg / L). The aim of this research was to determine the optimal medium for Exopolysaccharides (EPS) production by a Lactobacillus delbrueckii subsp. bulgaricus ropy strain isolated from a locally produced commercial fermented milk, in reconstituted skim milk (RSM) 10% (w/v), milk whey (MW), and soy milk whey (SMW), under optimal growth conditions for this strain. Milk whey was made by coagulating fresh milk using papaya latex 3% (v/v); soy milk whey was obtained from tofu household industry. The chemical composition of the substrate media was determined by proximate analysis, and sterilization was accomplished in an autoclave at 121°C for 15 min. Culture media were inoculated with 1% (v/v) of a starter culture of L. delbrueckii subsp. bulgaricus and then incubated at 30°C for 16 hr. EPS production, lactic acid content, cell counting, and pH were determined after the media were cooled at 5°C. Findings showed that on the basis of the growth characteristics of L. delbrueckii subsp. bulgaricus, the best medium for EPS production was RSM 10% (258.60 ± 26.86 mg/L) compared to the milk whey (69.60 ± 9.48 mg/L) and soy milk whey (49.80 ± 9.04 mg/L).