Malaysian Journal of Analytical Sciences Vol 23 No 5 (2019): 870 - 879

AN ASSESSMENT OF FT-IR AND FT-NIR CAPABILITY IN SCREENING CRUDE PALM OIL AUTHENTICITY AND QUALITY COMBINED

WITH CHEMOMETRICS

(Satu Penilaian Terhadap Kebolehan FT-IR Dan FT-NIR Untuk Menyaring Kesahihan dan Kualiti Minyak Sawit Mentah Digabung Dengan Kemometri)

Ng Jing Sheng¹, Widad Fadhullah^1,2, Mohd Omar Ab Kadir¹, Ainolsyakira Mohd Rodhi³, Noor Hana Hanif Abu Bakar⁴, Syahidah Akmal Muhammad^1,3*

¹Environmental Technology Division, School of Industrial Technology,

Universiti Sains Malaysia, 11800 USM, Penang, Malaysia

²Environmental and Occupational Health Program, School of Health Sciences, Health Campus,

Universiti Sains Malaysia, 16150 USM, Kubang Kerian, Kelantan, Malaysia.

³Analytical Biochemistry Research Centre

⁴School of Chemical Sciences

Universiti Sains Malaysia, 11800 USM, Penang, Malaysia

*Corresponding author: syahidah.muhammad@usm.my

Received: 16 January 2019; Accepted: 26 August 2019

Abstract

This study was conducted to assess the authenticity and evaluate the quality of palm oil with the aid of mid-infrared and near-infrared spectroscopy. Experiments were carried out to imitate the effect of frying in food service industry, therefore crude palm oil (CPO) samples were fried with different meat products (beef, mutton, fish, pork) at varying frequency of 3, 10, 20 and 30 times. Then the used frying oils were mixed with fresh and authentic CPO at different proportions, 5, 10, 20 and 30 (m/m %). Discriminant analysis on the infrared spectrum was carried out and the analysis was based on two class classification, which is to separate between 2 classes of samples. The results showed that the analysis with mid-IR spectrum successfully classified the adulterated oil samples from the authentic CPO with 2 misclassifications of adulterated oil into the authentic group out of 66 samples. The performance index of this model was 95.1 based on the Mahanalobis distance. The success rate of authentication was 96.7% for the mid-IR spectrum. However, the NIR spectrum analysis showed different results from the mid-IR as 11 adulterated samples out of 66 samples showed false positive result. The performance index of this model was 85.7 and the success rate of authentication was 83.3%. On the other hand, for the work on the classification of oil quality using mid-IR, the success rate was only 42.4% with the performance index of 73.4. Additionally, the NIR model for oil quality discrimination had 36.4% of success rate with a performance index of 56.4. The evaluation of oil quality based on the frequency of frying was not very successful and further work will be carried out. Overall, the authentication of palm oil was quite successful, but the evaluation of the quality of palm oil did not achieve our current objective. These rapid screening techniques, which are mid-infrared and near infrared spectroscopy have been proven to be useful for the authentication of edible palm oil but the evaluation of quality has to be further improved.

Keywords: crude palm oil, authenticity, mid-infrared, near-infrared, discriminant analysis

Abstrak

Kajian ini telah dijalankan untuk menilai kesahihan dan kualiti minyak sawit dengan bantuan spektroskopi inframerah-tengah dan hampir. Eksperimen dijalankan dengan menggoreng minyak sawit mentah (CPO) dengan beberapa jenis produk daging haiwan (daging lembu, kambing, ikan dan khinzir) bertujuan untuk meniru kesan menggoreng makanan dalam industri perkhidmatan makanan, dengan kekerapan yang berbeza iaitu 3, 10, 20 dan 30 kali. Minyak goreng tersebut kemudian telah dicampur dengan minyak sawit mentah dengan peratusan berbeza iaitu 5, 10, 20 dan 30 (m/m %). Selepas itu, spektrum inframerah telah digunakan untuk menjalankan analisis diskriminan dengan menggunakan kemometrik. Analisis diskriminan ini merupakan analisis berasaskan 2 kelas, dan analisis ini berkeupayaan untuk membezakan 2 kelas yang berbeza. Keputusan menunjukkan bahawa analisis specktrum inframerah-tengah telah berjaya mengasingkan minyak goreng terpakai daripada minyak tulen dengan hanya 2 pengelasan salah daripada 66 sampel. Indeks prestasi untuk model ini ialah 95.1 berdasarkan jarak Mahalonobis. Kadar berjaya bagi model ini ialah 96.7%. Seterusnya, model spektrum inframerah-hampir menunjukkan keputusan yang berbeza daripada inframerah-tengah kerana terdapat 11 sampel daripada 66 sampel telah diklasifikasi sebagai positif palsu. Indeks prestasi untuk model ini merupakan 85.7 dan kadar berjaya untuk klasifikasi kesahihan minyak ialah 83.3%. Manakala, dalam bahagian penilaian kualiti minyak menggunakan inframerah-tengah, kadar berjaya hanya 42.4% dengan indeks prestasi sebanyak 73.4. Seterusnya, penilaian kualiti minyak goreng dengan menggunakan model inframerah-hampir menunjukkan kadar berjaya sebanyak 36.4% dan indeks prestasi serendah 56.4. Penilaian kualiti minyak goreng berdasarkan kekerapan menggoreng adalah kurang berjaya dan kajian lebih lanjut akan dijalankan pada masa yang akan datang. Secara keseluruhannya, pengesahan kesahihan minyak sawit adalah berjaya tetapi penilaian kualiti minyak masih tidak dapat mengecapi objektif kajian ini. Teknik pemeriksaaan pantas ini, iaitu spektroskopi inframerah-tengah dan hampir telah dibuktikan berkesan untuk pengesahan kesahihan minyak sawit tetapi penilaian kualiti masih memerlukan penambahbaikan.

Kata kunci: minyak sawit mentah, kesahihan, inframerah-tengah, inframerah-hampir, analisis diskriminan

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