Validation study of lactose quantification method and milk adulteration by 1H NMR
Name: DANYELLE ALVES DA CUNHA
Type: PhD thesis
Publication date: 06/03/2020
Advisor:
Name |
Role |
|---|---|
| ÁLVARO CUNHA NETO | Advisor * |
Examining board:
| Name |
Role |
|---|---|
| ÁLVARO CUNHA NETO | Advisor * |
| EMANUELE CATARINA DA SILVA OLIVEIRA | External Examiner * |
| LUCIO LEONEL BARBOSA | External Examiner * |
| PAULO ROBERTO FILGUEIRAS | Internal Examiner * |
| VALDEMAR LACERDA JUNIOR | Internal Examiner * |
Summary: Milk can be defined as a homogeneous mixture of substances such as lactose, proteins, glycerides, among others. Among carbohydrates, lactose stands out, i.e., a disaccharide composed of glucose and galactose, present in bovine milk in a concentration of 4.6 %. According to Resolution No. 135 of the National Health Surveillance Agency (ANVISA), dairy products labeled as lactose free must contain lactose content equal to or less than 1 mg.mL-1. Thus, the objective of this work was to develop and validate a method for quantifying the lactose content by Nuclear Magnetic Resonance (NMR). The validation of the developed method followed the norms foreseen by Resolution RDC nº 166 of ANVISA, and presented excellent linearity, demonstrated by the value of R> 0.990 and the homoscedasticity of the results, as well as values of precision, accuracy and robustness less than 5%, besides of LD and LQ values of 0.135 mg.mL-1 and 0.407 mg.mL-1, respectively. Therefore, the method can be used as an alternative to quantify lactose in milk mainly due to the analysis time of only 36 min. Linked to consumption, the index of non-conformities and possible adulterations of milk and dairy products in Brazil is also quite expressive, as disclosed in the Yearbook of Animal Control Programs of the Animal Products Inspection Department (DIPOA ), is around 20 %. Among the most used techniques for the study of this milk are infrared, Raman, ultraviolet and NMR. However, according to a vast search in research bases, few studies involving milk on NMR. Thus, this study has the objective of detecting the adulteration of commercial UHT milks by NMR in the time domain (NMR-DT) and compare the results with tests performed by MAPA. The analysis of UHT milk adulterations with water, starch, hydrogen peroxide and sodium hypochlorite showed LD and LQ around 3 % v/v and 10 % v/v, respectively, and with sodium hydroxide it was 0.06 and 0.19 mg.mL-1, respectively. Thus, in a single rapid (2 min) and non-destructive analysis, DT-NMR was able to detect the adulteration of milk with different adulterants, eliminating the laborious task of carrying out different experiments for different adulterations.
