Inactivation of murine norovirus by high pressure processing in strawberry, raspberry and blackcurrant puree matrices

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Title: Inactivation of murine norovirus by high pressure processing in strawberry, raspberry and blackcurrant puree matrices
Alternative title: Hiiren noroviruksen inaktivointi korkeapainekäsittelyllä mansikka-, vadelma- ja mustaherukkasoseissa
Author: Solastie, Anna
Other contributor: Helsingin yliopisto, Maatalous-metsätieteellinen tiedekunta
University of Helsinki, Faculty of Agriculture and Forestry
Helsingfors universitet, Agrikultur- och forstvetenskapliga fakulteten
Publisher: Helsingin yliopisto
Date: 2020
Language: eng
Thesis level: master's thesis
Degree program: Mikrobiologian ja mikrobibiotekniikan maisteriohjelma
Master's Programme in Microbiology and Microbial Biotechnology
Magisterprogrammet i mikrobiologi och mikrobibioteknik
Specialisation: ei opintosuuntaa
no specialization
ingen studieinriktning
Abstract: Human norovirus (HuNoV) is the leading cause of foodborne illness globally. Especially minimally processed goods such as berries and shellfish are common sources of HuNoV outbreaks. High pressure processing (HPP) is a relatively novel food processing technology that can both inactivate foodborne pathogens and extend the shelf-life of food items in cold temperatures. HPP is especially suitable for fresh purees, juices and sauces. In this study, we used murine norovirus strain MNV-1 to model the inactivation of HuNoV by HPP in three berry puree matrices and phosphate-buffered saline (PBS). We assessed the effect of HPP by cell-based TCID50 infectivity assay and real-time reverse transcription quantitative PCR (RT-qPCR) with RNase and porcine gastric mucin (PGM) binding assay. We strived to find if there were differences between distinct pressures (4500 and 6000 bars) and hold times (3, 6, and 9 minutes) to efficiently inactivate MNV-1 in berry purees. We observed that the matrix type affected the survival of MNV-1 significantly both during HPP and transportation. During transportation, MNV-1 survived better in PBS than in berry purees. MNV-1 was efficiently inactivated in PBS leading to >3-log10 reductions in the number of infectious particles (TCID50/ml) at both 4500 and 6000 bars. In berry puree matrices, MNV-1 was most efficiently inactivated in blackcurrant puree resulting in ≈3-log10 reductions in genome equivalents. The efficacy of pressures and hold-times could not be differentiated in any of the used matrices. MNV-1 in raspberry puree showed no infectivity in RAW 264.7 cells but displayed ≈2-log10 reductions in genome equivalents. MNV-1 in strawberry puree displayed <1-log10 reductions in RAW 264.7 cells. Our results imply that PGM binding assay and RNase as pre-RT-qPCR treatments have problems in selecting infectious MNV-1 particles for amplification. Hence when using these pre-treatments, concluding on MNV-1 infectivity should be done cautiously.
Subject: murine norovirus
high pressure processing
berry puree
PGM binding assay
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