Comparison of DNA quality in raw and reconstituted milk during sterilization

Abstract

Responses to milk sterilization are usually evaluated only in terms of physicochemical properties and microbial safety, thus undervaluing the importance of DNA quality in an authentication process by methods based on PCR. Because DNA is a heat-sensitive molecule, we hypothesized that the heating process may impair the detection or quantification of DNA in raw fresh milk (FM) or reconstituted milk (RM), and that differences in DNA quality might exist between FM and RM. We thus investigated the effects of sterilization on the quality of DNA extracted from FM or RM; differences in DNA quality between FM and RM were also evaluated. The quality of extracted DNA from FM or RM was assessed by the specific detection of FM or RM composition in goat milk mixtures using primers targeting the bovine 12S gene, as well as by monitoring DNA yield, purity, ratio of mitochondrial (mt) to nuclear (n) DNA, and the level of DNA degradation. Polymerase chain reaction readily detected both untreated and heat-treated FM or RM in cow-goat milk mixtures, and gave a good sensitivity threshold (0.1%) under all sterilization conditions. The DNA yield and mtDNA:nDNA ratio of FM and RM varied significantly during the sterilization process. These results demonstrated that the sterilization altered the quantification of DNA in FM or RM during sterilization, but DNA could still be readily detected in sterilized FM or RM by PCR. Furthermore, we noted significant differences in DNA integrity, yield, and mtDNA:nDNA ratio between FM and RM during sterilization, which may have potential as a means to distinguish FM and RM.

Extraction and detection of DNA from UHT milk during storage

“…Compared with the positive control, all the extracted DNA samples showed serious smearing and the fragment length is between 100 bp and 2000 bp, which is shorter than the positive control, indicating that UHT treatment severely degraded the DNA in the milk. This result is similar to the previous report, which suggested that the DNA extracted from raw milk will gradually degrade into small fragments when the raw milk was treated by autoclaving from 0 min to 15 min (Liao et al, 2018a). In addition, there were no obvious differences in DNA degradation at different storage stages of UHT milk.…”

“…Mislabels and ingredient substitutions of food are major issues in the food industry (Cawthorn et al, 2013;Everstine et al, 2013;Wong & Hanner, 2008). To ensure food quality, the DNA-based method has been a reliable, accurate, and speedy tool to correct mislabeling (Liao et al, 2017a(Liao et al, , 2018a. However, the PCR-based method largely depends on the purity and intactness of DNA extracted from food (Spaniolas et al, 2008).…”

The combined use of 1H and 2D NMR‐based metabolomics and chemometrics for non‐targeted screening of biomarkers and identification of reconstituted milk

“…The 1 H-13 C HMBC is useful to research the correlation between 13 C nuclear and 1 H nuclear. Through the correlation between 13 C and 1 H nuclear, substances identified by 1 H NMR spectra can be confirmed further. And the results showed that the qualitative result was reliable.…”

“…been reported that the content of furosine is only affected both by heating temperature and also by storage time and conditions. 7,8 For example, the furosine and lactulose content is changed when the storage temperature reaches 30 ∘ C. 3 Some techniques have been developed to detect reconstituted milk, such as front-face fluorescence spectroscopy, 9 matrix-assisted laser desorption / ionization time of flight mass spectrometry (MALDI-TOF MS), 10 high-performance liquid chromatography (HPLC), 11,12 polymerase chain reaction (PCR), 13 and capillary zone electrophoresis with ultraviolet detection (CZE-UV). 14 However, sample pretreatments for these methods are complex and time consuming, so there is a need to develop a rapid, accurate, and simple method for the identification of reconstituted milk and UHT milk.…”

DNA-based approaches for dairy products authentication: A review and perspectives

“…These treatments cause the degradation of DNA molecules (J. Liao, Yang, Sheppard, & Liu, 2018). In terms of purity and PCR inhibitors presence, lower purity of DNA was observed in heat-treated milk powder due to denatured proteins that can co-precipitate with genomic DNA, comparing with DNA purity obtained from raw milk (J Liao, Liu, Ku, et al, 2017).…”