The Influences of Organic Matter Concentrations in Juices for Pathogen Detection Using Phage-Based Biosensors

Abstract

Fruit and vegetables are playing an important role of today’s healthy diet. Juices are the liquid extracts from fruit and vegetables, which contain lots of organic matters, such as vitamins, minerals and plant chemicals (phytonutrients). Commercial bottle juices usually contain different percentages of real juices in their juice products. Therefore, the amount of organic matter content in juices are different in various brands of juices. The foodborne pathogen outbreaks through the consumption of fruit or vegetable juices continue to be reported (CDC, 2016). It indicates that pathogens like Salmonella can be packaged with juices even with current manufacture microbial-inactivation process. According to several studies, the acidity in tomatoes juice and the phyto-chemicals (like chlorophyll) from damage leaves in leafy greens samples can affect the sensitivity of pathogen detection in juices. For example, chlorophyll is one of the substances in leafy green juice that inhibits PCR reaction for pathogen detection. This made the pathogen detection in some juices a difficult task to achieve. The phage magnetoelastic (ME) biosensors are wireless sensors, whose resonance oscillation and resonance frequency are actuated and detected through magnetic fields. These biosensors have been shown to be highly sensitive and specific in pathogen detection including Salmonella on various food surfaces or liquids (Li et al., 2010). Therefore, in this study, different concentrations of juices from tomatoes and spinach with artificially spiked Salmonella (at the concentration of 104 cfu/ml) was tested by ME biosensors. The influence of pathogen detection capability was then studied by comparing the bacterial capture rates on biosensors. In tomato juice, the results showed that the capture rate of Salmonella can be reached up to 90.68% by using 100 ME biosensors in a tube rocking experiment with 10% tomato juice content. In spinach juice, the capture rate of Salmonella showed similar results as 90.68% in the same 10% juice concentration. However, when the juice concentration of spinach went up to 15% and 20%, the bacterial capture rate slightly decreased. The Salmonella capture rate were shown as 89.82% and 89.065, respectively. The decreasing of capture rate was obvious by using 50 ME sensors for the 15% and 20% spinach juices. In conclusion, by using 100 phage ME biosensors, the detection platform can detect as high as 89% Salmonella in high juice concentration (15 % and 20%) of both tomato and spinach juice samples. While in the moderate juice concentration zone (5-10%), the ME biosensors show very promising results of detecting 90% Salmonella in both juices.