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Sains Malaysiana 47(11)(2018): 2677–2683 http://dx.doi.org/10.17576/jsm-2018-4711-10
Rapid Microbial Detection Model System
in UHT Milk Products using Poly(L-Lactic
Acid) (PLLA) Thin Film (Sistem Pengesanan Mikrob Model Pantas di dalam Produk Susu UHT
menggunakan Filem
Nipis (PLLA) Poli
(Asid L-Laktik)) NURUL HIDAYAH
YUSOF,
NORRAKIAH
ABDULLAH
SANI,
FARAH
HANNAN
ANUAR,
MOHD
SUZEREN
JAMIL
& SAIFUL IRWAN ZUBAIRI* Centre for Biotechnology & Functional
Food, Faculty of Science and Technology, Universiti
Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia Diserahkan: 9 Februari
2018/Diterima: 17 Julai
2018 ABSTRACT Ultra-high temperature is a
process that involves heating of milk to a very high temperature
to produce sterile milk products. However, food poisoning due
to consumption of UHT
milk still happen in Malaysia. This study was done
to develop a film that is made by poly(L-lactic
acid) (PLLA)
to detect the presence of microorganisms in UHT milk
products. UHT milk that was used in this study was full cream milk.
Contaminated milk that contained Bacillus
cereus was made to conduct a model system on the relationship
between colony forming unit of microorganisms and contact angle.
Contaminated milk was also used as a control sample to study the
difference of milk properties between fresh and contaminated milk.
Physicochemical analysis (Brix, colour, pH and contact angle) and microbiological analysis
(total plate count) were done to UHT milk sample as soon as the
packaging of the milk was unsealed. Analysis was done with 30
min time interval until 4 h and 30 min since the unsealing of
packaging. The results showed that presence of microorganisms
in UHT milk was detected after the
milk product was unsealed and exposed to environment for 3 h and
30 min. Contact angle resulted from the presence of microorganisms
in UHT milk
was 64.34 - 65.44° with its colony forming unit, 2.1 – 3.9 cfu/mL. Therefore, the potential usage of contact angle on PLLA
thin film with respect to colony forming unit (cfu) in detecting the presence of microorganisms in UHT
milk product was attained and well modelled. Keywords: Contact angle; microorganisms;
PLLA; spoilage indicator; UHT
milk ABSTRAK Rawatan suhu ultra-tinggi merupakan proses yang melibatkan
pemanasan susu
kepada suhu
yang amat tinggi bagi
menghasilkan produk
susu yang steril. Walau bagaimanapun, keracunan makanan akibat pengambilan susu UHT masih berlaku di Malaysia. Kajian ini dijalankan
untuk membangunkan
satu filem yang diperbuat daripada PLLA
bagi mengesan
kehadiran mikroorganisma
dalam produk susu UHT. Susu
UHT
yang digunakan dalam
kajian ini
adalah susu
krim penuh.
Susu terkontaminasi yang mempunyai Bacillus cereus dihasilkan untuk menjalankan sistem model berkenaan hubungan antara unit pembentukan koloni mikroorganisma dengan sudut sentuh.
Susu terkontaminasi
juga digunakan sebagai sampel kawalan untuk mengkaji perbezaan sifat susu bagi
susu segar
dengan susu terkontaminasi.
Analisis fizikokimia
(Brix, warna dan
sudut sentuh) dan
analisis mikrobiologi
(hitungan piring jumlah) dijalankan ke atas sampel
susu UHT sebaik sahaja selepas
pembungkusan susu
dibuka. Analisis dijalankan dengan sela masa 30 min sehingga selepas empat jam dan 30 min pembungkusan dibuka. Keputusan menunjukkan kehadiran mikroorganisma dalam susu UHT dikesan
selepas produk susu dibuka dan
didedahkan kepada
persekitaran selama tiga jam dan 30 min. Sudut sentuh yang dihasilkan akibat kehadiran mikroorganisma dalam produk susu
UHT
adalah 64.34 - 65.44°
dengan unit pembentukan koloni, 2.1 - 3.9 cfu/mL. Oleh yang demikian,
potensi penggunaan
sudut sentuh pada
permukaan filem
nipis PLLA terhadap
unit pembentukan koloni
dalam pengesanan mikroorganisma di dalam produk susu
UHT
telah diperoleh
dan dimodelkan
dengan berkesan. Kata kunci: Indikasi
kerosakan; mikroorganisma;
PLLA; sudut sentuh; susu
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untuk surat-menyurat;
email: saiful-z@ukm.edu.my
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