Recent Developments in Non-thermal Processess - Food and Industrial Bioproducts and Bioprocessing - page 307

vitamin B group and folates, lipid-soluble vitamins such as vitamin E, K, carotenoids
(vitamin A) and anthocyanins) will not be affected by HPP processing. However, some
factors, such as high oxygen concentration, combined high temperature and high pressure
treatment and other chemical reactions, may degrade the bioactive compounds to some
extent (Oey et al ., 2008a). Regarding sensory properties, HPP has a limited effect on
pigments (e.g. chlorophyll, carotenoids, anthocyanins, etc.) responsible for the color of
fruits and vegetables (Oey et al ., 2008). Numerous studies using both trained panelists
and consumers have shown no difference among HPP-treated and fresh samples regarding
food flavor (Parish, 1998; Fernández-García et al ., 2001 ; Baxter et al ., 2005 ; Laboissière
et al ., 2007). However, during shelf-life, sensory properties can be altered due to
incomplete inactivation of enzymes and microorganisms, resulting in undesired chemical
reactions (both enzymatic and non-enzymatic) in the food matrix. These reactions are also
influenced by the type of packaging, oxygen concentration in the package and storage
temperature.
HPP was one of the first non-thermal technologies developed and implemented in food
industry. At the beginning of the 1990s, two companies in Japan commercialized HPP-
treated marmalades, vegetable-based sauces and fruit juices (Thakur and Nelson, 1998).
Applications of HPP technology in industry are growing, including a wide range of products
in the meat industry (cured jam, bacon and turkey, pork sausages, foie gras, marinated raw
meat and “ready to eat” meat products), seafood products (oysters, lobster and crab meat)
and vegetable products (fruit juices and smoothies, fruit purees, fresh cut fruits, guacamole,
jams, deli salads, dressings, sauces and “ready to eat” vegetable dishes) (Tonello, 2008).
Several companies in the United States, Europe and Asia design and market HPP industrial-
and laboratory-scale equipment. Avure technologies Inc. in the USA and NC Hyperbaric in
the European Union are the world-leading HHP equipment manufacturers. The industrial
equipment is designed with a capacity up to 350 liters (single vessel) or 600 liters (two
vessels) and provide pressures up to 600 MPa with a maximum overall production around
5000 kg/h, depending on the holding time and package size. Food is usually packaged in a
flexible plastic material with minimal headspace to minimize the volume variation (15%)
during the treatment (van der Berg et al ., 2002). The development of industrially reliable
equipment has lowered the estimated cost of HPP to US$0.05-0.5 per liter (Balasubramian,
2003). Recently, the US Food and Drug Administration (FDA) accepted pressure-assisted
thermal-sterilization (PATS) as a process for commercial application in low acid foods
(National Center for Food Safety and Technology, 2009). Combined high temperature and
high pressure treatment brings a new challenge for the equipment manufacturers in the
design of a vessel that is able to resist compression and heating forces in a large volume. The
scientific community needs to assess the impact of this new process on the quality and
nutritional content of the HPP-sterilized food. Only pilot-scale equipment was available for
the PATS process in 2010.
13.2.2 Ultra High Pressure Homogenization (UHPH)
Homogenization is a well-known fluid mechanical process that involves the division of
particles or droplets into micron sizes (0.2-2 μm) by passing the fluid through a minute gap
in a homogenization valve, creating a stable dispersion or emulsion (Diels and Michiels,
2006). Homogenization at relatively low pressure (50 MPa) has been extensively used in
many industries, such as the pharmaceutical, cosmetic, chemical and dairy industries (i.e. to
reduce the fat globule size) (Diels et al ., 2005a ). Recently developed robust homogenization