Judul: Pengaruh pengeringan semprot terhadap ketahanan Enterobacter sakazakii (Cronobacter spp.) dalam susu skim bubuk
Abstrak: Enterobacter sakazakii (Cronobacter spp.) which was associated with meningitis and necrotizing enterocolitis (NEC) in preterm neonates, infant, and low weight birth has been isolated in PIF in Indonesia. PIF can be contaminated by Enterobacter sakazakii (Cronobacter spp.) because it is not a sterile product. During PIF production, pasteurization is a step aimed to kill Enterobacter sakazakii (Cronobacter spp.) and other vegetative pathogens. However, processing steps after pasteurization may introduce the pathogens to the products. Therefore the effect of drying on the survival of Enterobacter sakazakii (Cronobacter spp.) need to be evaluated. The objective of this study is to evaluate the effect of spray drying on the survival of several of Enterobacter sakazakii (Cronobacter spp.) strains. This study consist of preliminary and main study. Preliminary studies aimed to determine the best inlet temperature for drying, quality of the resulted powdered skim milk and two most heat resistant strains by rapid screening of six Enterobacter sakazakii (Cronobacter spp.) strains (DESb7a, DES b7b, DESb10, DES c3, DES c13, and DES d3) at 54°C for 32 minutes. The main study was conducted on the two most heat resistant strains (DES b7a and DESb10), YRc3a, and ATCC51329. The bacterial culture was inoculated into ±40% reconstituted skim milk at 107 – 108 cfu/g and dried in a Buchi Mini Spray Drier at 160°C, 170°C, and 180°C inlet temperature and 82°C outlet temperature. The resulting skim milk powder was subsequently analyzed for the Enterobacter sakazakii (Cronobacter spp.) survival. Spray drying at the studied temperatures killed substantial numbers of Enterobacter sakazakii (Cronobacter spp.) but did not yield Enterobacter sakazakii (Cronobacter spp.)–free powder at the levels of contamination used. At an inlet temperature of 160°C, log reduction of Enterobacter sakazakii (Cronobacter spp.) ranged from 2,54 to 3,07 depending upon Enterobacter sakazakii (Cronobacter spp.) strains. Survival of Enterobacter sakazakii (Cronobacter spp.) decreased as spray drying temperature increased. The log reduction of Enterobacter sakazakii (Cronobacter spp.) at inlet temperature of 170°C ranged from 2,77 to 3,25 while at inlet temperature of 180°C, the log reduction ranged from 3,24 to 3,55 of the four strains. YRc3a was the most heat tolerant Enterobacter sakazakii (Cronobacter spp.) strain during spray drying.
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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: Teknik penentuan posisi bintang berdasarkan pelat foto overlapping
Abstrak: Bintang adalah salah satu objek langit yang menarik untuk diamati. Untuk itu, pengetahuan tentang posisi bintang sangat diperlukan. Posisi bintang di langit dapat dihitung melalui foto bintang. Fotografi astronomi atau astrometri merupakan ilmu yang mempelajari metode untuk menentukan posisi bendabenda langit seperti bintang berdasarkan pelat foto (Kamp, 1967). Sebuah pelat foto berisi citra bintang-bintang yang sudah diketahui posisinya berdasarkan katalog dan citra bintang-bintang yang belum diketahui posisinya. Posisi bintang yang ada di katalog dinyatakan dengan (a,3). Bintang yang belum diketahui posisinya lebih banyak jumlahnya daripada bintang yang sudah diketahui posisinya. Citra bintang pada pelat foto berupa sebuah titik dalam bentuk tetap. Posisinya pada pelat merupakan hasil pengukuran pada bidang kartesius dan dinyatakan dengan (1;,fl). Hasil pengukuran tersebut kemudian direduksi menjadi koordinat terukur (x,y). Hubungan antara (a,3) dan (x,y) didekati dengan sebuah deret dengan konstanta-konsranta deret merupakan konstanta pelat. Nilai konstanta pelat diperoleh dengan menggabungkan hasil pengukuran posisi bintang pada masing-masing pelat menjadi sebuah persamaan normal (Jefferys, 1963). Hasil akhir dari gugus persamaan normal tersebut dijabarkan dalam bentuk nOlasi matriks partisi dan berupa sebuah sistem persamaan linier Ax = b di mana A adalah matriks jarang, dan x merupakan konstanta pelar yang akan dicari nilainya. Untuk menyelesaikan sistem persamaan linier terse but digunakan metode transformasi given. Konstanta pelat yang sudah diperoleh dengan menyelesaikan sistem persamaan linier di atas, kemudian disubtitusi ke sebuah persamaan untuk memperoleh posisi bintang yang tidak tercantum dalam katalog. .
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