M: Food Microbiology & Safety Osmosonication of Blackberry Juice: Impact on Selected Pathogens, Spoilage Microorganisms, and Main Quality Parameters Eric Wong, Fabrice Vaillant, and Ana P´ erez Abstract: Osmosonication combines ultrasound with nonthermal concentration. It was applied on tropical highland blackberry (Rubus adenotrichus) juice over different periods of time to assess reductions in microorganism and the impact on main quality parameters. This juice had been inoculated with Salmonella spp., Shigella sp., a lactic acid bacterium, yeasts, and molds. It was then sonicated for 5.9 to 34.1 min at 20 kHz and 0.83 W/mL. Nonthermal concentration was simulated by mixing the juice with a concentrate to obtain 650 g TSS/kg. It was then stored at −18 ◦ C for up to 82 h. The lactic acid bacterium, yeasts, and molds were reduced by 1.60 to as much as 5.01 log 10 CFU/mL, whereas, for pathogens, reductions were total ≥7.1 log 10 CFU/mL after 24 h of storage, even for juice not sonicated, because of low pH. Color, antioxidant capacity, anthocyanins, and ellagitannins did not change significantly during sonication treatment up to 32 min. However, an off-flavor was detected after 8 min of sonication. Nonetheless, osmosonication can be considered as an alternative to thermal processes for producing safe and high-quality concentrates. Keywords: food safety, fruit juice, microbial survival, nonthermal concentration, sonication Practical Application: Osmosonication represents a potential processing alternative for producing safe and high-quality concentrated fruit juice without applying thermal treatments. Findings reported in this article can also be applied by industries when concentrating juices by classical means at relatively low temperature. It provides industries with a mathematical model specific for blackberry juice, from which different combinations of sonication time and storage time of concentrate can be chosen to achieve safety and quality goals. Introduction Consumers are increasingly demanding minimal processing of natural fruit juices. In response, numerous innovative technologies, mainly low-temperature processing, have been developed. How- ever, 1 consequence is that the microbiological safety of these beverages is often at risk. Indeed, processing at relatively low tem- perature has been responsible for an increased number of outbreaks of foodborne illnesses in last decades (Beuchat 1996; CDC 1999; CDC 2000). Pathogens such as Salmonella spp., Shigella sp., Listeria monocytogenes, and Escherichia coli O157:H7 have been associated with the consumption of unpasteurized apple juice, apple cider, tomato juice, and orange juice (Parish 1997; Krause and others 2001). The main challenge for food technologists is, therefore, to de- velop juice stabilization processes that comply with higher food safety requirements while preserving sensorial, nutritional, and functional properties (Gould 2001). The U.S. Food and Drug MS 20100232 Submitted 3/3/2010, Accepted 5/25/2010. Authors Wong and P´ erez are with Centro Nac. de Ciencia y Tecnolog´ ıa de Alimentos (CITA), Univ. de Costa Rica (UCR), Ciudad Universitaria Rodrigo Facio, C´ odigo Postal 11501-2060, San Jos´ e, Costa Rica. Author Vaillant is with Centre de Coop´ eration Internationale en Recherche Agronomique pour le D´ eveloppement (CIRAD), UMR 95 QUALISUD, TA B-95/16, 73 rue Jean-Franc ¸ois Breton, 34398 Montpellier Cedex 5, France. Direct inquiries to author Vaillant (E-mail: fabrice.vaillant@cirad.fr). Administration (FDA) requires fruit juices to be treated nonther- mally, with a minimal reduction of 5 log 10 for pathogens (FDA 2001; Van Opstal and others 2006). Consequently, most nonther- mal processes need to combine with other hurdle technologies to ensure a significant reduction of not only pathogens, but also spoilage microorganisms that may reduce food quality. Osmotic evaporation (OE) is an emerging technology that oper- ates at ambient temperatures but allows fruit juices to concentrate to 650 g TSS/kg (total soluble solids per kilogram) while preserv- ing all nonvolatile molecules and most aroma compounds (Barbe and others 1998; Vaillant and others 2001; Cisse and others 2005). Although such high osmotic pressure reduces microbial survival (Poirier and others 1998; Mille and others 2002; Mille and oth- ers 2005), such reduction may not be sufficient in terms of food safety. Other nonthermal hurdle technologies must, therefore, be incorporated to ensure that the microorganism load that naturally contaminates fruit juices is sufficiently reduced. Treatment of liquid food products with ultrasonic radiation, also referred as sonication, has been combined with other process- ing steps to reduce microbial contamination (Piyasena and oth- ers 2003). Oscillatory high pressure on fluids by ultrasonic waves induces membrane damages and even cell disruption during se- vere treatment. However, sonication is often not effective alone but when combined with heat (thermosonication), high dynamic pressure (manosonication), or both (thermo-manosonication), it significantly reduces time, temperature, and dynamic pressure for the same F -value (Pagan and others 1999; Wu and others 2008; C  2010 Institute of Food Technologists R  M468 Journal of Food Science  Vol. 75, Nr. 7, 2010 doi: 10.1111/j.1750-3841.2010.01730.x Further reproduction without permission is prohibited