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: Survival dan pertumbuhan Cronobacter sakazakii dan Lactobacillus selama rekonstitusi susu formula
Abstrak: Cronobactersakazakii (Enterobacter sakazakii) is an emerging foodborne pathogenassociated with powdered infant formula(PIF). The bacterium has been known to cause necrotizing enterocolitis(NEC), meningitis, and sepsis in neonates, especially to those born prematurely and or with low birth weight. C.sakazakiicould be found and survive in PIFas a residual contamination during drying or filling (after pasteurization process) and reconstitution practice in household or hospitals.Recently, somePIF product is being added with Lactobacillus as probiotics, therefore the reconstitution temperature may affect both the Lactobacillus and C. sakazakii. The objectives of this study are to study (1)the influence of various temperature of the water (30, 50, and 70oC) used for reconstitution on (a) the survival and growth of C. sakazakii in PIF, (b) the survival and growth of C. sakazakii and Lactobacillus R23 present together in PIF, and (2) to determine selective enumeration media of C. sakazakii and Lactobacillus R23 when both are present in PIF. A preliminary study was conducted for rapid screening of six isolates to obtain two heat tolerant C. sakazakii isolates by using heat treatment at 54oC for 32 minutes. The main study was evaluation of survival and growth of C. sakazakii YR c3a in PIF followingreconstitution at the above temperatures in the absence or presence of Lactobacillus R23 for up to eight hours. C. sakazakii YR c3a and DES b7b were selected as the more heat tolerant. Reconstitution at 30 and 50 oC did not influence survival and growth of C. sakazakii for up to 8 h hang time.Two log reductionsof C. sakazakii occurred in PIF reconstituted with water at 70oC.At 30 oC, presence of Lactobacillus R23 in PIF also did not affect the survival and growth of C. sakazakii upon reconsitution at irrespective of the initial load ratio. Meanwhile presence of Lactobacillus did not affect C. sakazaki upon reconstitution at 50 oC when the ratio of LactobacillusR23 : C. sakazakiiYR c3a was 1:1, but growth of C. sakazakii YR c3a decreased following reconstitution when ratio of the two bacteria was 103:1.Reconstitution at 70 oC reduced the number of C. sakazakii YR c3a and DES b7b by 2.51 and 2.48 log CFU/ml, respectively. In PIF containing Lactobacillus, regardless of the ratio, Lactobacillus R23 and C. Sakazakii YR c3adecreased for up to <1,00 log CFU/ml and to 1,40 log CFU/ml, respectively. Following reconstitution at this temperature, the growth of C. sakazakiiYR c3a started tobe observed 4 h afterward while Lactobacillus R23 started to increase 2 h afterward.
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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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