Lactose quantification in UHT milk by high-performance liquid chromatography and cryoscopy (freezing point depression)

Cleiver Júnio Martins Costa,Camila Alves Moreira,Milla Gabriela Dos Santos,Amado Jésus Silva,Ricardo Corrêa De Santana,Juliana Karla De Souza Teixeira Almeida

doi:10.33448/rsd-v10i15.23224

Cleiver Júnio Martins Costa, Camila Alves Moreira + Show 4 more

Open Access

https://doi.org/10.33448/rsd-v10i15.23224

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Abstract

Due to the large number of people with lactose maldigestion, the dairy industries have increased production and diversity of low lactose and lactose-free foods. Consequently, the need to control the lactose hydrolysis process has also risen. This study aimed to correlate freezing point depression (cryoscopy) and lactose concentration, quantified by high-performance liquid chromatography (HPLC), in UHT milk. To accomplish this, UHT milk samples were subjected to seven lactose hydrolysis treatments, using lactase enzyme, resulting in different lactose concentrations. All samples were subjected to HPLC analysis and freezing point measurement, using a cryoscope. The results were plotted on a graph and a linear regression was performed. There was a strong correlation between lactose concentration and freezing point (R = 0,9973) and the coefficient of determination (R2) was 0,9946, which means that 99,46% of the variability of the response data is explained by the linear regression model. Therefore, the results point to the feasibility of estimating the lactose concentration in milk during the hydrolysis process for the production of low lactose milk, by cryoscopy, a quick analysis, with lower cost compared to HPLC and that is already among the analyses commonly performed in dairy industries.

Highlights

Milk and its derivatives are very nutritious foods and have a prominent role in human nutrition, providing high-quality proteins, minerals and vitamins
The hydrolysis time, the reduction in the lactose concentration, leads to a decrease in the freezing point of the milk (P < 0,05), which tends to become as far from 0 °C the lower the lactose concentration, which is consistent with the results obtained by Costa et al (2019a) and Costa et al (2019b)
Trevisan (2008), analyzing samples of pasteurized semi-skimmed milk (~ 1% fat), found a difference in the cryoscopy index greater than 30% between samples of milk with and without lactose, corroborating the results found in the present study

Summary

Introduction

Milk and its derivatives are very nutritious foods and have a prominent role in human nutrition, providing high-quality proteins, minerals and vitamins For this reason, the consumption of these products is especially important in all age groups (Mckinley, 2005; National Center of Public Health Protection [NCPHP], 2006; Ordóñez, 2005). To prevent people with deficiency lactose digestion from stopping ingesting milk nutrients, especially calcium and high-quality proteins, the global dairy industry started the development products with low content and lactose-free, in which the lactose is hydrolyzed by the addition of exogenous lactase, β-galactosidase (E.C. 3.2.1.23) (Churakova et al, 2019)

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