IDENTIFICATION OF PROTEIN MOLECULAR WEIGHT IN BREAST MILK BEFORE AND AFTER 3 DAYS OF STORAGE USING SODIUM DODECYL SULFATE POLYCRYLAMIDE GEL ELECTROPHORESIS (SDS-PAGE)

Nurlaela, Refa (2025) IDENTIFICATION OF PROTEIN MOLECULAR WEIGHT IN BREAST MILK BEFORE AND AFTER 3 DAYS OF STORAGE USING SODIUM DODECYL SULFATE POLYCRYLAMIDE GEL ELECTROPHORESIS (SDS-PAGE). Diploma thesis, UNIVERSITAS BAKTI TUNAS HUSADA TASIKMALAYA.

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Abstract

Abstrak Protein Air Susu Ibu (ASI) memiliki peran krusial dalam pertumbuhan dan perkembangan bayi, namun stabilitas komponen bioaktif selama penyimpanan menjadi perhatian penting dalam praktik laktasi. Penelitian ini bertujuan menganalisis perubahan profil protein ASI sebelum dan setelah penyimpanan 3 hari pada suhu 4°C menggunakan metode Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE). Sampel ASI diperoleh dari ibu menyusui sehat dan dianalisis pada hari ke-0 (kondisi segar) serta setelah penyimpanan 3 hari pada suhu 4°C. Ekstraksi protein dilakukan melalui sentrifugasi bertingkat dengan wash buffer, diikuti analisis elektroforesis gel poliakrilamid 12% dengan volume sampel optimal 2-3 μL dan kuantifikasi densitometri menggunakan software ImageJ. Hasil menunjukkan profil protein ASI segar terdiri dari kasein (MW ~25 kDa, intensitas 2847,5 ± 156,2 AU), β-laktoglobulin (MW ~18 kDa, intensitas 1254,3 ± 87,5 AU), dan α-laktalbumin (MW ~14 kDa, intensitas 892,6 ± 62,3 AU). Setelah penyimpanan 3 hari, terjadi degradasi protein signifikan dengan penurunan intensitas kasein 7,86% (2623,8 ± 142,7 AU), β-laktoglobulin 5,15% (1189,7 ± 95,2 AU), dan α-laktalbumin 6,46% (834,9 ± 58,7 AU). Kasein menunjukkan stabilitas relatif lebih baik dibandingkan protein whey, namun degradasi tetap terjadi. Temuan mengkonfirmasi bahwa meskipun penyimpanan ASI 4°C selama 3 hari masih dalam batas aman panduan klinis, degradasi protein dapat mempengaruhi kualitas nutrisi dan bioaktivitas, memberikan dasar ilmiah untuk optimasi protokol penyimpanan dan edukasi praktis pentingnya meminimalkan durasi penyimpanan ASI. Kata kunci: Air Susu Ibu, protein, penyimpanan, SDS-PAGE, degradasi, stabilitas Abtract Human milk protein plays a crucial role in infant growth and development, but the stability of bioactive components during storage is an important concern in lactation practice. This study aims to analyze changes in human milk protein profiles before and after 3 days of storage at 4°C using the Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE) method. Breast milk samples were obtained from healthy lactating mothers and analyzed on day 0 (fresh condition) and after 3 days of storage at 4°C. Protein extraction was performed through stepwise centrifugation with wash buffer, followed by 12% polyacrylamide gel electrophoresis analysis with an optimal sample volume of 2-3 μL and densitometric quantification using ImageJ software. The results showed that the protein profile of fresh breast milk consisted of casein (MW ~25 kDa, intensity 2847.5 ± 156.2 AU), β-lactoglobulin (MW ~18 kDa, intensity 1254.3 ± 87.5 AU), and α-lactalbumin (MW ~14 kDa, intensity 892.6 ± 62.3 AU). After 3 days of storage, significant protein degradation occurred with a decrease in casein intensity of 7.86% (2623.8 ± 142.7 AU), β-lactoglobulin by 5.15% (1189.7 ± 95.2 AU), and α-lactalbumin by 6.46% (834.9 ± 58.7 AU). Casein showed relatively better stability compared to whey proteins, but degradation still occurred. The findings confirm that although storing breast milk at 4°C for 3 days is still within the safe limits of clinical guidelines, protein degradation can affect nutritional quality and bioactivity, providing a scientific basis for optimizing storage protocols and practical education on the importance of minimizing breast milk storage duration. Keywords: Breast milk, protein, storage, SDS-PAGE, degradation, stability

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