Lipase/Esterase Activity as an Indicator of Milk Spoilage Process: A Sequential Injection Analysis Methodology

Milk quality is essential to ensure the excellence of dairy products and consumer safety. However, cold chain storage and transportation do not always prevent milk contamination, compromising its quality. This study aims to analyze the physical, chemical, and biological variables involved in milk spoilage, identifying indicators that facilitate its monitoring through a lab-made sequential injection analysis (SIA) system. The study was conducted on batches of milk refrigerated and at room temperature, revealing that changes in bacterial concentration and the activity of hydrolytic enzymes, particularly lipases, esterases, and proteases are key determinants of milk deterioration. To measure hydrolytic activity, the conventional method was adapted, validated, and automated on the SIA system detecting lipase/esterase activities in milk. The results of the SIA method compared to the microplate yielded similar results, demonstrating that the SIA is an effective and reliable technique for real-time monitoring of milk deterioration.