Decreasing incubation temperature r

Decreasing incubation temperature resulted in increased incubation time necessary for the pH to reach
4.4. The Tukey test showed that the incubation time required in order for the pH value to reach 4.4 is
greater at 20C than at 25C or 30C. Incubation temperature of 30C caused the time needed for the pH
to reach 4.4 to exhibit the lowest value. Similar results were reported for yogurt samples incubated at
37C, 40C, 43C and 46C [9]. According to the authors, the increase in the time needed for the pH to
reach 4.4 with reducing incubation temperature can be attributed to the reduced activity of the bacteria.
The addition of caseinates in the milk used for kefir fermentations reduced the observed rate of pH
reduction. According to Tukey test the incubation time of the kefir samples with and without caseinates
increased in the following order: 0% caseinates = 1% caseinates < 2% caseinates = 3% caseinates. The
increase in the time needed for the pH to reach 4.4 with increasing casein concentration can be attributed
to the increased buffering capacity of the milk used for kefir production. Caseins have strong buffering
capacity [10], resulting to increased incubation time for the pH to reach 4.4 when they are added to milk.
Yogurt samples made from milk with a caseinate to whey protein ratio of 1/1 showed faster rate of
acidification when compared with samples made from milk where the caseinate to whey protein ratio was
4/1 [11]. Furthermore, during acidification of kefir the precipitation of caseins results to the formation of
larger clusters when caseinates are added. These clusters block the transport of lactose resulting to a
nonhomogeneous fermentation environment with regards to lactose concentration and consequently to a
reduced lactose hydrolysis rate and lactc acid formation [10].
According to the flow curves of the samples (Figures 1 and 2), kefir behaves as a pseudoplastic fluid
with its viscosity reducing with increasing shear rate. Figure 1 shows the flow curves of the kefir samples
incubated at 20C, 25C and 30C with the addition of caseinates at 3% concentration. As it can be seen
kefir sample incubated at 25C showed the highest viscosity, followed by the sample incubated at 20C,
while the sample incubated at 30C exhibited the lowest viscosity. Similar behaviour was exhibited by the
kefir samples made without the addition of caseinates and with the addition of caseinates at 1% and 2%
concentration.
As it can be seen in Figure 2, the addition of caseinates causes the viscosity of the kefir samples to
increase. Kefir samples incubated at 20C and 30C exhibited similar behaviour.
The values of the flow behaviour index obtained from the flow curves of the samples are shown in
Table 2. Kefir samples that exhibited increased viscosity showed also increased pseudoplastic behaviour
(decreased values of the flow behaviour index). According to ANOVA, both incubation temperature
(p

Hasil (Bahasa Indonesia) 1:

Penurunan suhu inkubasi mengakibatkan waktu inkubasi peningkatan yang diperlukan untuk pH untuk mencapai4.4. tes Tukey menunjukkan bahwa waktu inkubasi yang diperlukan dalam rangka untuk nilai pH untuk mencapai 4.4lebih besar pada 20C daripada 25C atau 30C. Inkubasi suhu 30C disebabkan waktu yang diperlukan untuk pHuntuk mencapai 4.4 menunjukkan nilai terendah. Hasil yang sama dilaporkan untuk sampel yoghurt diinkubasi di37C, 40C, 43C dan 46C [9]. Menurut penulis, peningkatan waktu yang diperlukan untuk pHmencapai 4.4 dengan mengurangi inkubasi suhu dapat dikaitkan dengan penurunan aktivitas bakteri.Penambahan caseinates dalam susu yang digunakan untuk kefir fermentations mengurangi tarif diamati pHpengurangan. Menurut Tukey tes waktu inkubasi kefir sampel dengan dan tanpa caseinatesmeningkat dengan urutan sebagai berikut: 0% caseinates = 1% caseinates < 2% caseinates = 3% caseinates. Themeningkatkan waktu yang diperlukan untuk pH untuk mencapai 4.4 dengan meningkatnya kasein konsentrasi bisa dihubungkanuntuk peningkatan kapasitas buffer digunakan untuk produksi kefir susu. Caseins memiliki kuat bufferingkapasitas [10], mengakibatkan peningkatan waktu inkubasi untuk pH untuk mencapai 4.4 ketika mereka ditambahkan ke susu.Sampel yoghurt yang terbuat dari susu dengan caseinate whey protein rasio 1/1 menunjukkan tingkat lebih cepat daripengasaman bila dibandingkan dengan sampel yang terbuat dari susu mana caseinate whey protein rasio adalah4/1 [11]. Furthermore, during acidification of kefir the precipitation of caseins results to the formation oflarger clusters when caseinates are added. These clusters block the transport of lactose resulting to anonhomogeneous fermentation environment with regards to lactose concentration and consequently to areduced lactose hydrolysis rate and lactc acid formation [10].According to the flow curves of the samples (Figures 1 and 2), kefir behaves as a pseudoplastic fluidwith its viscosity reducing with increasing shear rate. Figure 1 shows the flow curves of the kefir samplesincubated at 20C, 25C and 30C with the addition of caseinates at 3% concentration. As it can be seenkefir sample incubated at 25C showed the highest viscosity, followed by the sample incubated at 20C,while the sample incubated at 30C exhibited the lowest viscosity. Similar behaviour was exhibited by thekefir samples made without the addition of caseinates and with the addition of caseinates at 1% and 2%concentration.As it can be seen in Figure 2, the addition of caseinates causes the viscosity of the kefir samples toincrease. Kefir samples incubated at 20C and 30C exhibited similar behaviour.The values of the flow behaviour index obtained from the flow curves of the samples are shown inTable 2. Kefir samples that exhibited increased viscosity showed also increased pseudoplastic behaviour(penurunan nilai indeks perilaku aliran). Menurut ANOVA, suhu inkubasi kedua(p < 0.001) dan penambahan caseinates (p < 0.001) mempengaruhi secara signifikan indeks perilaku aliran. Kefirsampel yang diinkubasi di 30C dipamerkan nilai tertinggi jika dibandingkan dengan sampel diinkubasi di 20C atau25C. ada perbedaan yang signifikan untuk nilai-nilai indeks perilaku aliran terjadi antara sampel diinkubasipada 20C dan 25C. Indeks aliran perilaku dari sampel penurunan sebagai konsentrasi kasein itumeningkat. Menurut Tukey tes indeks aliran perilaku dari sampel kefir meningkat dimengikuti urutan: 3% caseinates < 2% caseinates < 1% caseinates < 0% caseinates.