Judul: Sintas Bakteri Asam Laktat Kandidat Probiotik Kering Beku Asal Air Susu Ibu Selama Rekonstitusi dan Kemampuannya untuk Berkompetisi dengan Cronobacter sakazakii
Abstrak: Powdered infant formula (PIF) is a fabricated food product whose nutrition is formulated to correspond to breast milk. Nowadays, some PIF manufacturers have supplemented PIF with probiotic bacteria. However, due to possible Cronobacter spp. contamination, reconstitution at 70 oC is adviced thus it may also affect the viability of lactic acid bacteria (LAB). The objective of this study was to evaluate the survival of freeze dried LAB isolated from breast milk during reconstitution and their ability to compete with Cronobacter sakazakii (C. sakazakii) in PIF. This study was conducted in 4 stages, i.e. (1) screening of LAB isolates based on the survival during reconstitution at 50 oC; (2) competition of LAB isolates with C. sakazakii YRC3a; (3) evaluation of the LAB isolates on freeze drying process; and (4) competition of LAB isolates with C. sakazakii YRC3a in PIF at various reconstitution temperatures. Screening of LAB showed that all LAB isolates decreased in cell number after reconstitution at 50 oC. Based on the result of screening, 4 LABs were chosen i.e Lactobacillus rhamnosus (L. rhamnosus) R14, R21, R23, and R25 because the bacterial number decrease was lower. However, only L. rhamnosus R21 and R25 were capable of inhibiting the growth of C. sakazakii YRC3a. Meanwhile, assessment of the LAB survival during freeze drying process showed insignificant reduction of cell number of L. rhamnosus R21 and R25. Competition of freeze dried L. rhamnosus R21 and R25 with C. sakazakii YRC3a during reconstitution in PIF at various reconstitution temperatures (50, 60, and 70 oC) showed that the freeze dried LAB were able to suppress the number of C. sakazakii YRC3a as the temperature increased. The result also showed that LAB isolates did not undergo significant cell reduction as the reconstitution temperature increased.
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Judul: Kemampuan Campuran Bakteri Asam Laktat Kandidat Probiotik Asal Air Susu Ibu Berkompetisi dengan Cronobacter sakazakii pada Susu Formula Rekonstitusi
Abstrak: Cronobacter sakazakii is an emerging pathogen occasionally found in powdered infant formula (PIF) and causes ilnessess in certain groups of infants. To achieve the minimum risk level of C. sakazakii it is recommended to carry on reconstitution of PIF at temperature of 70 °C or more. The recommended temperature may therefore influence the presence of lactic acid bacteria (LAB) commonly added as probiotic in PIF and other milk powder. The objectives of this study were to determine the antimicrobial activities of cocktail of L. rhamnosus isolated from breast milk against C. sakazakii, to evaluate the effect of the reconstitution temperature towards the survival and growth of L. rhamnosus and C. sakazakii, and to determine the influence of L. rhamnosus on the growth of C. sakazakii after reconstitution. L. rhamnosus cocktail was more effective in inhibiting the growth of single strain C. sakazakii than cocktail of C. sakazakii. The use of cocktail of L. rhamnosus R21 & R25 could inhibit the growth of C. sakazakii YR c3a by 3.75 log CFU/mL. At the same time, the growth of cocktail of L. rhamnosus was not affected by the presence of C. sakazakii. Addition of cocktail of L. rhamnosus R21 & R25 in reconstituted powdered infant formula did not influence the growth of C. sakazakii significantly. Survival of C. sakazakii was influenced by reconstitution temperatures.
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Judul: Penentuan Nilai Eigen dan Vektor Eigen dari Matriks Tridiagonal 2-Toeplitz dengan Pendekatan Polinomial Chebyshev
Abstrak: The eigenvalues and eigenvectors of a matrix can be determined by finding its characteristic polynomials. The characteristic polynomials of a tridiagonal 2-Toeplitz matrix is shown to be closely connected to polynomials which satisfy the Chebyshev recurrence relationship. If the order of the matrix is odd, then the eigenvalues are found explicitly in terms of the Chebyshev zeros and the eigenvectors are found in terms of the polynomials satisfying the recurrence relationship. For even ordered matrices, the situation is more complicated. The problem in these cases is that although the Chebyshev recurrence formula is still applied, its initial values are not generating Chebyshev polynomials
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