Effect of food components and processing parameters on DNA degradation in food

Abstract

The effect of food components on degradation of DNA by DNase I (EC 3.1.21.1) was monitored by electrotransformation of Escherichia coli, making it possible to determine the number of plasmid molecules capable of giving rise to transformed cells. The transformation frequency increased linearly with the plasmid number within the range of 2 × 10 6 to 2 × 10 10 . DNA degradation was reduced by one order of magnitude in the presence of 0.05% (w.v -1 ) maltol or 1 mM putrescine. Complete inhibition of degradation was observed with ≥0.2% (w.v -1 ) maltol, ≥0.01% (w.v -1 ) octyl gallate or ≥0.5 mM of spermine. To monitor degradation of plant DNA during food processing, a real-time PCR system was established. The ratio of copy numbers of a potato gbss DNA fragment of 325 bp and a nested 96 bp fragment was determined. The latter served as internal reference for normalization. The system made it possible to exclude process-dependent changes of DNA concentration in the food matrix. Processing of genetically modified potatoes to dried potato sticks, crisps or flakes was studied and drying steps were shown to exert the strongest effect on DNA degradation, resulting in a drop of the ratio from 0.73 to 0.16.

Combined effects of temperature, pressure and low pH on the amplification of DNA of plant derived foods

“…The food processing triggers off DNA degradation and may affect DNA-based food analysis (Bauer et al 2003(Bauer et al , 2004Tilley 2004;Yioshimura et al upper: 1 -standard 100 bp; 2 -negative control (116 bp); 3 -raw sample; 4 -pH 7.6, 2 min; 5 -pH 2.25, 2 min; 6 -pH 7.6, 5 min; 7 -pH 2.25, 5 min; 8 -pH 7.6, 10 min; 9 -pH 2.25, 10 min; 10-11 -negative control (469 bp); 12 -raw sample; 13 -pH 7.6, 2 min; 14 -pH 2.25, 2 min; 15 -pH 7.6, 5 min; 16 -pH 2.25, 5 min; 17 -pH 7.6, 10 min; 18 -pH 2.25, 10 min Lower: 1 -standard 100 bp; 2 -negative control (116 bp); 3 -raw sample; 4 -pH 7.6, 10 min; 5 -pH 2.25, 10 min; 6 -pH 7.6, 20 min; 7 -pH 2.25, 20 min; 8 -pH 7.6, 30 min; 9 -sample of preserved (Commercial Products); 10-11 -negative control (469 bp); 12 -raw sample; 13 -pH 7.6, 10 min; 14 -pH 2.25, 10 min; 15 -pH 7.6, 20 min; 16 -pH 2.25, 20 min; 17 -pH 7.6, 30 min; 18 -pH 2.25. 30 min 2004; Moreano et al 2005;Gryson et al 2008;ISO 2005) of GM and non-GM plant samples.…”

Antimicrobial Resistance in the Food Chain: A Review

“…However, the complex food matrix and the food processing environment (e.g., biofilms) can protect the DNA as is shown in sausages [58]. DNA can also be protected by individual food components (e.g., arginine, maltol) [57,59]. The stability of DNA during food processing is an inverse function of the DNA length [60,61].…”

Stress- and Growth Rate-Related Differences between Plate Count and Real-Time PCR Data during Growth of Listeria monocytogenes

“…It is not to be expected that L. monocytogenes might grow into stationary phase in food, but stress conditions imposed on the bacteria during food processing and storage might be enough to induce substantial cell death. However, the persistence of dead cells and extracellular DNA depends on the condition of bacterial cells before death, the chemical and physical composition of the environment (bound DNA might be protected from degradation), and microbial activity (6,24,28). Others also reported overquantification of different bacteria by realtime PCR in relation to stress and composition of the samples: overquantification of Bifidobacterium longum but not Bifidobacterium lactis by real-time PCR during fermentation of oat drink was observed, overquantification of E. coli in activated sludge was more pronounced at stages with lower microbial activity, and numbers of Pseudomonas fluorescens EPS62e determined with real-time PCR were similar to plate count data for apple blossoms but not for apple leaves because stresses were higher on the latter (22,24,32).…”