Mitochondrial DNA Fragmentation as a Molecular Tool to Monitor Thermal Processing of Plant-Derived, Low-Acid Foods, and Biomaterials

作者：Caldwell Jane M^*; Perez Diaz Ilenys M; Sandeep K P; Simunovic Josip; Harris Keith; O**orne Jason A; Hassan Hosni M

来源：Journal of Food Science, 2015, 80(8): M1804-M1814.

DOI：10.1111/1750-3841.12937

• mitochondrial DNA
• quantitative PCR
• thermal processing

Cycle threshold (Ct) increase, quantifying plant-derived DNA fragmentation, was evaluated for its utility as a time-temperature integrator. This novel approach to monitoring thermal processing of fresh, plant-based foods represents a paradigm shift. Instead of using quantitative polymerase chain reaction (qPCR) to detect pathogens, identify adulterants, or authenticate ingredients, this rapid technique was used to quantify the fragmentation of an intrinsic plant mitochondrial DNA (mtDNA) gene over time-temperature treatments. Universal primers were developed which amplified a mitochondrial gene common to plants (atp1). These consensus primers produced a robust qPCR signal in 10 vegetables, 6 fruits, 3 types of nuts, and a biofuel precursor. Using sweet potato (Ipomoea batatas) puree as a model low-acid product and simple linear regression, Ct value was highly correlated to time-temperature treatment (R-2 = 0.87); the logarithmic reduction (log CFU/mL) of the spore-forming Clostridium botulinum surrogate, Geobacillus stearothermophilus (R-2 = 0.87); and cumulative F-value (min) in a canned retort process (R-2 = 0.88), all comparisons conducted at 121 degrees C. D-121 and z-values were determined for G. stearothermophilus ATCC 7953 and were 2.71 min and 11.0 degrees C, respectively. D-121 and z-values for a 174-bp universal plant amplicon were 11.3 min and 9.17 degrees C, respectively, for mtDNA from sweet potato puree. We present these data as proof-of-concept for a molecular tool that can be used as a rapid, presumptive method for monitoring thermal processing in low-acid plant products.
Practical Application This method could be used as another tool for thermal process validation and monitoring. It is especially useful for thermal processes over 100 degrees C, since temperatures above boiling rapidly damage DNA. Its advantages over enzymatic assays are that mtDNA is highly stable and can be stored at freezing temperatures for long periods. Mitochondrial DNA can be used for all plant products tested. Processors will be able to validate processes and track process deviations using rapid molecular methods. Processors can use this presumptive test prior to shipping out a product.

• 出版日期2015-8