Pomegranate (Punica granatum, Punicaceae) is highly valued mainly
due to its exceptional and unique sensory and nutritional properties
(López-Rubira, Conesa, Allende, & Artés, 2005). Polyphenols are the
major class of pomegranate phytochemicals, including flavonoids (anthocyanins),
condensed tannins (proanthocyanidins) and hydrolysable
tannins (ellagitannins and gallotannins) (Jaiswal, DerMarderosian, &
Porter, 2009). It has been reported that consumption of pomegranate
fruits has nutritional and medical benefits, including reduced oxidative
stress, atherogenic modifications to LDL, and platelet aggregation, as
well as anticancer, antibacterial, and antiviral activities (Qu, Pan, &
Ma, 2010). Therefore, there is a need for alternative methods of processing
which can increase microbiological stability and preserve nutritional
and bioactive characteristics (Patras, Brunton, Da Pieve, &
Butler, 2009). Consumer demand for freshly squeezed fruit juices is
increasing, but such products are susceptible to spoilage and thus
have a limited shelf-life (Buzrul, Hami, Largeteau, & Demazeau, 2008).
Thermal processing (pasteurization) is the most commonly used preservation
technique to extend the shelf life of juices. However, this processmay
have adverse effects on sensory and nutritional values of juices
(Plaza et al., 2006).Therefore, color quality of anthocyanin containing
juices is undesirably lost during thermal process (Patras, Brunton,
O'Donnell, & Tiwari, 2010). Food scientists and the food industry are
therefore searching for novel methods, which can destroy undesirable
microorganisms with less adverse effects on product quality. Several
methods have been investigated for extending the shelf life of food.
Non-thermal processing technologies for food preservation and safety
are gaining widespread acceptance throughout the food industry. An
example is high hydrostatic pressure (HHP) technology, which has
been identified as a method for inactivating microorganisms
(Patterson, 2005) and the processing temperature does not increase beyond
40 °C (Welti-Chanes, Ochoa-Velasco, & Guerrero-Beltrán, 2009).
This technology transmits isostatic pressure instantly to the product,independent of size, shape and food composition (Patras et al., 2009).
Food treated in this way has been shown to keep its original freshness,
flavor, taste and color changes which are minimal (Dede, Alpas, &
Bayindirli, 2007).Moreover, it can be used to inactivate microorganisms
and enzymes (Bayindirli, Alpas, Bozoglu, & Hızal, 2006). The application
of HHP treatment ranging from 100 to 1000 MPa in order to inactivate
pathogenic and spoilage microorganisms without affecting the quality
of foods and has a comparable preservation effect with thermal treatment
(Raso & Barbosa-Cánovas, 2003). HHP in combination with packaging
of good barrier properties can prevent browning in minimally
processed products during storage in the sealed pack (Perera,
Gamage,Wakeling, Gamlath, & Versteeg, 2009).
The required pressure treatment for microbiologically safe and stable
products is dependent on the target microorganism to be inactivated.
Bacterial vegetative cells, yeasts andmolds are sensitive to pressures between
200 and 700 MPa. Various factors influence the pressureresistance
of microorganisms, including the target microorganism and
its physiological state, the intrinsic properties of the menstruum, and
the processing temperature, time and magnitude of pressure treatment
(Bull et al., 2004). Polydera, Stoforos, and Taoukis (2005) have reported
that a high pressure treatment of 600 MPa at 40 °C for 4 min led to a better
retention of ascorbic acid during post processing storage of fresh orange
juice at 0–30 °C compared to conventional thermal pasteurization
(80 °C, 60 s). Due to the benefits of extension of shelf-life, superior organoleptic
quality and better nutrient retention described above, high
hydrostatic pressure technology is an advantageous alternative process
for high valued products. Also, other researchers (Houska et al., 2006)
have reported that high pressure pasteurization process (500 MPa for
10 min) is capable of inactivating more than 5 log orders of the viable
microorganisms present originally in the raw broccoli juice and product
is free of coliform bacteria, yeast, molds and salmonella during 30 days
of storage at the chilled room temperature conditions (temperature up
to 5 °C).
Effects of HHP (300–500 MPa/25 °C/10 min) on microbial inactivation
and processing qualities of tomato juices during refrigerated
storage at 4 °C for 28 days were investigated to compare with those
of conventionally thermal processing by Hsu, Tan, and Chi (2008).
Total viable counts of tomato juices treated by 300 and 400 MPa decreased
0.9 and 1.5 log units, respectively; and after storage, they
slightly elevated to 4.6 and 3.1 log CFU ml−1. Also, this study demonstrated
that 500-MPa processing would be an alternative for conventionally
t
Pomegranate (Punica granatum, Punicaceae) is highly valued mainlydue to its exceptional and unique sensory and nutritional properties(López-Rubira, Conesa, Allende, & Artés, 2005). Polyphenols are themajor class of pomegranate phytochemicals, including flavonoids (anthocyanins),condensed tannins (proanthocyanidins) and hydrolysabletannins (ellagitannins and gallotannins) (Jaiswal, DerMarderosian, &Porter, 2009). It has been reported that consumption of pomegranatefruits has nutritional and medical benefits, including reduced oxidativestress, atherogenic modifications to LDL, and platelet aggregation, aswell as anticancer, antibacterial, and antiviral activities (Qu, Pan, &Ma, 2010). Therefore, there is a need for alternative methods of processingwhich can increase microbiological stability and preserve nutritionaland bioactive characteristics (Patras, Brunton, Da Pieve, &Butler, 2009). Consumer demand for freshly squeezed fruit juices isincreasing, but such products are susceptible to spoilage and thushave a limited shelf-life (Buzrul, Hami, Largeteau, & Demazeau, 2008).Thermal processing (pasteurization) is the most commonly used preservationtechnique to extend the shelf life of juices. However, this processmayhave adverse effects on sensory and nutritional values of juices(Plaza et al., 2006).Therefore, color quality of anthocyanin containingjuices is undesirably lost during thermal process (Patras, Brunton,O'Donnell, & Tiwari, 2010). Food scientists and the food industry aretherefore searching for novel methods, which can destroy undesirablemicroorganisms with less adverse effects on product quality. Severalmethods have been investigated for extending the shelf life of food.Non-thermal processing technologies for food preservation and safetyare gaining widespread acceptance throughout the food industry. Anexample is high hydrostatic pressure (HHP) technology, which hasbeen identified as a method for inactivating microorganisms(Patterson, 2005) and the processing temperature does not increase beyond40 °C (Welti-Chanes, Ochoa-Velasco, & Guerrero-Beltrán, 2009).This technology transmits isostatic pressure instantly to the product,independent of size, shape and food composition (Patras et al., 2009).Food treated in this way has been shown to keep its original freshness,flavor, taste and color changes which are minimal (Dede, Alpas, &Bayindirli, 2007).Moreover, it can be used to inactivate microorganismsand enzymes (Bayindirli, Alpas, Bozoglu, & Hızal, 2006). The applicationof HHP treatment ranging from 100 to 1000 MPa in order to inactivatepathogenic and spoilage microorganisms without affecting the qualityof foods and has a comparable preservation effect with thermal treatment(Raso & Barbosa-Cánovas, 2003). HHP in combination with packagingof good barrier properties can prevent browning in minimallyprocessed products during storage in the sealed pack (Perera,Gamage,Wakeling, Gamlath, & Versteeg, 2009).The required pressure treatment for microbiologically safe and stableproducts is dependent on the target microorganism to be inactivated.Bacterial vegetative cells, yeasts andmolds are sensitive to pressures between200 and 700 MPa. Various factors influence the pressureresistanceof microorganisms, including the target microorganism andits physiological state, the intrinsic properties of the menstruum, andthe processing temperature, time and magnitude of pressure treatment(Bull et al., 2004). Polydera, Stoforos, and Taoukis (2005) have reportedthat a high pressure treatment of 600 MPa at 40 °C for 4 min led to a betterretention of ascorbic acid during post processing storage of fresh orangejuice at 0–30 °C compared to conventional thermal pasteurization(80 °C, 60 s). Due to the benefits of extension of shelf-life, superior organolepticquality and better nutrient retention described above, highhydrostatic pressure technology is an advantageous alternative processfor high valued products. Also, other researchers (Houska et al., 2006)have reported that high pressure pasteurization process (500 MPa for10 min) is capable of inactivating more than 5 log orders of the viablemicroorganisms present originally in the raw broccoli juice and productis free of coliform bacteria, yeast, molds and salmonella during 30 daysof storage at the chilled room temperature conditions (temperature upto 5 °C).Effects of HHP (300–500 MPa/25 °C/10 min) on microbial inactivationand processing qualities of tomato juices during refrigeratedstorage at 4 °C for 28 days were investigated to compare with thoseof conventionally thermal processing by Hsu, Tan, and Chi (2008).Total viable counts of tomato juices treated by 300 and 400 MPa decreased0.9 and 1.5 log units, respectively; and after storage, theyslightly elevated to 4.6 and 3.1 log CFU ml−1. Also, this study demonstratedthat 500-MPa processing would be an alternative for conventionallyt
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