Effect of high pressure processing against spoilage microorganisms, and on Listeria and E. coli contamination in a mixed fruit and vegetable smoothie

JAGUS, R.J.; DENOYA, G.I.; AGÜERO, M.V.; VAUDAGNA, S.R.; FERNANDEZ MARÍA VERÓNICA

Salerno

Workshop; International Nonthermal Processing Workshop and Short course 2018; 2018

The availability of sugar, nutrients and high aw make fruit and vegetable (F&V) beverages susceptible to microbial growth, one of the main causes of spoilage. Additionally, reports indicate that pathogenic species like Listeria monocytogenes and Escherichia coli O157:H7, among others, can survive in these products during long periods of storage. High Pressure Processing (HPP) is proposed as an alternative treatment able to improve microbiological stability and to assure food safety, while preserving sensory and nutritional characteristics of food products.The aim of this study was to evaluate the microbial stability of F&V smoothies treated with HPP during 28 days of storage at 5ºC. Additionally, the effectiveness against Listeria innocua (LI) and Escherichia coli (EC) inoculated cells was determined during 12 days of storage at abuse temperature (15°C).The ingredients (orange 59%, apples 15%, carrots 15%, beet leaves 6%, beet stems 5%) were washed, peeled, chopped and blended in a homogenizer. The smoothie was packed into polyethylene terephthalate bottles (100 mL) and then pressurized (600 MPa / 6 min/ 20 °C, treatment previously optimized). Mesophilic aerobic bacteria, Enterobacteriaceae and molds and yeasts counts were determined. In order to evaluate the treatment effectiveness, smoothies were inoculated with a 6 log CFU/g load of LI and EC. Treatment of smoothies with HPP reduced native microbiota counts below detection limit (DL= 1 log CFU/g) and allowed to maintain them until the end of storage, eliminating one of the main causes of spoilage of these products. Moreover HPP reduced the EC and LI initial loads to values below DL and allowed to keep them for at least 12 days at 15ºC. These results indicate that the high pressure treatment applied not only improved microbial stability of the products but also was effective against the inoculated microorganisms, ensuring safety even when a high load contamination occurs.