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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 Received: 9 February 2018/Accepted:
17 July 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;
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