HIGH PRESSURE PROCESSING AS A NOVEL TECHNOLOGY IN THE DAIRY INDUSTRY
ABSTRACT
Heat treatment has
historically been used to preserve food in order to inactivate unwanted
bacteria and extend its shelf life. Now a day, a non-thermal method to preserve
a variety of food products is high pressure processing (HPP). Different milk
proteins' size, shape, and structure are impacted by high pressure in the
100–1000 MPa range. Primary structure casein micelles are unaffected by low
pressure, but they break down at high pressure (300 MPa). It has been found
that a pressure treatment of at least 400 MPa for 15 minutes is necessary to
give thermally pasteurized milk a shelf-life of 10 days at 10 °C. The amount of
microbial inactivation is influenced by the pressure used, the duration of the
treatment, the temperature, surrounding conditions, and the kind and quantity
of bacteria. The dairy industry, which continually faces issues related to food
safety with its quality, has a wide range of opportunities due to pathogens or
spoilage microorganism inactivation without impacting the organoleptic
characteristic. A variety of synthetic additives, preservatives, emulsifiers,
stabilizers, antioxidants, colors, and sweeteners are used in the production of
dairy products for flavor, texture, increase shelf life, or replace protein or
fat. By which consumers are more willing to spend extra for natural products
with fewer ingredients, free of harsh processing and synthetic chemicals.
Technology based on high pressure is an effective option that ensures
nutritional quality and safety. This review focuses on advance knowledge
regarding the effects of high-pressure technology and its relevance to milk's
constituents.
Keywords: high pressure
processing, non-thermal method, preserve, pasteurized milk, nutritional
quality.
INTRODUCTION
The ongoing need for
milk and milk products around the world promotes the formation of modern dairy
farms, processing businesses. Modern advancements in the milk processing
industry have led to significant improvements in all unit operations, including
separation, standardization, pasteurization, homogenization, and packing. The
most effective way to remove germs or other biological entities from milk and
other foods without significantly raising the temperature is to use recently
discovered non-thermal processing techniques. By doing so, they can avoid a
series of unfavorable reactions in foods. Among the most popular non-thermal
processing technique is high-pressure processing (HPP). This advance milk
processing technique are used to increase milk's shelf life, improve the
nutritional value and safety of milk and milk products, and improve their
health benefits without changing their physicochemical properties. Today's
world needs most the implementation of technologies at all production stages,
from fodder cultivation to milk marketing. Emerging dairy processing
technologies that might reduce energy use and greenhouse gas emissions include
pulsed electric fields, high hydrostatic pressure, high-pressure
homogenization, microwave heating, microfiltration, pulsed light, UV light
processing, and carbon dioxide processing (Gebeyehu, 2023).
In order to
eliminate bacteria without significantly altering food's color, flavor, or
nutritional qualities, high pressure is used instead of heat. In this
technique, the food can be safely stored while retaining many of the qualities
of a fresh product. Furthermore, food can undergo rheological changes under
high pressure that have positive structural and sensory consequences (Datta
& Deeth, 1999; Goyal et al., 2013; Roobab et al., 2023).
In the first HPP
study, which was carried out in the US in 1885, it was revealed that high
pressurization eradicated out microorganisms, was the first to recognize the
possibilities of high-pressure food treatment in 1899. But until it was
"rediscovered" in the 1980s, it received not much attention. A number
of manufacturers in the United States, Spain, the United Kingdom, Japan, and
China have established the capability to build HPP equipment in recent years as
the technology has gradually advanced. Researchers later discovered that HPP
increased the shelf life of milk. These research showed how high pressure can
be used in the food sector. It is a potential replacement for pasteurizing
milk. High pressure (HP) causes the casein micelles in milk to break down into
smaller particles, resulting in a decrease in milk turbidity and lightness of
color as well as an increase in viscosity. In 1990, the first foods created
with this technique in Japanese market are yoghurts, fruit jellies, salad
dressings, and fruit sauces were among them. Other pressure-treated goods, such
as pressure pasteurized milk are being produced (Datta & Deeth, 1999; Goyal
et al., 2013; Roobab et al., 2023).
A non-thermal
technique for preserving and sterilizing milk and milk products that involves
applying extremely high pressure to the product in order to inactivate certain
bacteria and enzymes. According to studies on raw milk treated with high
pressure (HP), this treatment is just as effective at getting rid of harmful
and spoilage bacteria as pasteurization at producing raw milk of equivalent
quality. High pressure processing shown efficacy at inactivating bacteria in
both high- and low-acid food systems when compared to foods with a higher pH,
such as milk. By changing the basic characteristics of the milk's constituents,
it may have a positive effect on the attributes of treated milk. High-pressure
processing, a unique thermal processing alternative in the food and dairy
industries, includes a treatment chamber, a pressure generating system, a
pressure transmission medium, and a pressure intensifier (Gebeyehu, 2023;
Roobab et al., 2023; Stratakos et al., 2019).
HIGH PRESSURE PROCESSING IN
INDUSTRIES
High Pressure
Processing (HPP) is a specific application of high hydrostatic pressure to food
products for the purpose of pasteurization and preservation. In the context of
the food and dairy industry, it involves subjecting sealed food packages or
containers to elevated pressures. This process is designed to extend the shelf
life while maintaining its quality, freshness, and nutritional value (Goyal et
al., 2013; Huppertz, 2010).
Pascal's law states
that pressure reacts immediately, iso-statically, and uniformly subject to the
size and shape of the material. Foods are subjected to pressures ranging from
100 to 1,000 MPa during high-pressure processing. The method is typically batch-operated
and used with a variety of prepackaged liquid and semisolid foods as well as
food ingredients (Goyal et al., 2013; Huppertz, 2010).
According to Goyal
et al., 2013; Huppertz, 2010, the three steps of high-pressure processing are
as follows:
- An initial period needed to get to the
appropriate pressure, also known as the come-up time.
- A processing period at the desired pressure,
also known as the holding time.
- A brief period needed to let the pressure go, also known as the release time.
BIBLIOGRAPHY
Ø Datta, N., &
Deeth, H. C. (1999). High pressure processing of milk and dairy products.
Australian Journal of Dairy Technology, 54(1), 41-48.
Ø Gebeyehu, M. N.
(2023). Recent Advances and Application of Biotechnology in the Dairy
Processing Industry: A Review. Intensive Animal Farming-A Cost-Effective
Tactic.
Ø Goyal, A., Sharma,
V., Upadhyay, N., Sihag, M., & Kaushik, R. (2013). High pressure processing
and its impact on milk proteins: A review. J. Dairy Sci. Technol, 2(1),
2319-3409.
Ø Huppertz, T. (2010).
High pressure processing of milk. In Improving the safety and quality of milk
(pp. 373-399). Woodhead Publishing.
Ø Roobab, U.,
Inam-Ur-Raheem, M., Khan, A. W., Arshad, R. N., Zeng, X. A., & Aadil, R. M.
(2023). Innovations in high-pressure technologies for the development of clean
label dairy products: a review. Food Reviews International, 39(2), 970-991.
Ø Stratakos, A. C.,
Inguglia, E. S., Linton, M., Tollerton, J., Murphy, L., Corcionivoschi, N., ...
& Tiwari, B. K. (2019). Effect of high pressure processing on the safety,
shelf life and quality of raw milk. Innovative Food Science & Emerging Technologies,
52, 325-333.
ADVANTAGES OF HPP
High Pressure Processing (HPP) has emerged as a revolutionary technology in the dairy industry, offering advantages that significantly contribute to product quality, safety, and shelf life (Bello et al., 2014). One primary benefit of HPP is its ability to inactivate and disrupts the cellular structure of spoilage microorganisms like; Escherichia coli, Bacillus cereus, Pseudomonas fluorescens and Enterobacter aerogenes, while preserving the nutritional, sensory attributes and shelf life of dairy products (Rodriguez., et al 2005) Unlike traditional thermal processing methods, HPP operates at cold temperatures, preventing the denaturation of sensitive milk proteins and enzymes. Consequently, HPP-treated dairy products maintain their natural flavor, color, texture, and nutritional value, a crucial advantage for health-conscious consumers seeking minimally processed options (Tao et al., 2014).
One of the most promising applications of HPP is the production of high-quality cheeses from raw milk. HPP can be used to inactivate pathogenic bacteria in raw milk without compromising the flavor or texture of the cheese. This makes HPP an attractive alternative to pasteurization for cheesemakers who want to produce raw milk cheeses (Huppertz., et al 2011). Another key advantage of HPP that, it enhances product stability by applying high pressure. HPP slowing down enzymatic and oxidative reactions responsible for product deterioration. This not only extends the product's shelf life but also reduces the need for chemical preservatives and additives (Rastogi et al., 2007).
Furthermore, HPP facilitates product innovation in the dairy industry by enabling the creation of novel and value-added products. This technology allows for the incorporation of ingredients that are typically sensitive to heat, such as probiotics, vitamins, and bioactive compounds, into dairy formulations. Also HPP provide easy Extraction of valuable protein like pure alpha-lactalbumin and beta-lactoglobulin from whey These proteins can then be added to other foods to improve their nutritional value and functional properties (Balda et al., 2012). As a result, manufacturers can develop dairy products with enhanced functional and nutritional profiles, targeting specific health benefits. In conclusion, High Pressure Processing has led in a new era of innovation and quality improvement in the dairy industry. Its ability to maintain product integrity, enhance shelf life, and support novel product development makes it a valuable tool for dairy manufacturers (Rastogi et al., 2007; Mandal & Kant, 2017).
EFFECTS ON BACTERIAL FLORA
High-pressure processing
(HPP) effectively destroys microorganisms in food, particularly spoilage
causing microorganisms e.g. Pseudomonas, Clostridium, Bacillus and other
psychrotrophic or thermoduric found in milk (Quigleyet al., 2013). Generally,
in milk microbial inactivation requires pressures ranging from 200 to 600 MPa.
Gram-positive bacteria exhibit greater resistance to pressure as compared to
gram-negative bacteria, yeasts, and molds, due to the presence of teichoic acid
in their cell walls, which imparts rigidity (Alpas & Bozoglu, 2002; Naik et
al., 2013). Vegetative bacterial cells are inactivated at pressures between 400
and 600 MPa. When pressure is applied, there is a sudden destruction and loss
of cell membrane integrity, that makes them unable to reproduce. For instance,
goat milk processed at 500 MPa for 15 minutes proves as efficient as
pasteurized milk (Naik et al., 2013). Also (Lim et al., 2023) reported that
psychotropic and mesophilic spores were reduced to an undetectable level after
HPP treatment at 600 Mpa, 7 min. The level of pressure, along with other
factors such as holding time, temperature, and microbial growth phase,
influences the effectiveness of this process (Goyal et al., 2013). study found
that HPP treatment at 400 MPa for 5 minutes reduced the number of E. coli
bacteria in milk by 99.999%
High pressure processing
(HPP) cannot inactivate bacterial spores in milk. However, by optimizing HPP
conditions or combination with other treatments and agents, spores can be
inactivated. Some successful combination treatments are HPP with temperature combination
and oscillatory pressure cycle treatments (Zhang & Mittal, 2008).
EFFECT ON WHEY PROTEIN
In
milk two proteins are present dominantly casein and whey protein, these
Proteins can be modified in milk during HPP treatment. Denaturation caused by
HPP on whey proteins could be reversible or irreversible it depends upon the
holding time, pressure, temperature, and pH of milk. High pressure processing
leads to denaturation or aggregation β -lactoglobulins and α -lactalbumin which
is major components of whey protein in milk but still among both of them level
of α- lactalbumin denaturation was much lower than that for β- lactoglobulins.
β - lactoglobulins is most sensitive to HHP because β - lactoglobulins has only
two disulphide linkages and one free –SH group. So it is less rigid as compared
to α- lactalbumin which has four disulphide bonds. only about 10% of the α-
lactalbumin was denatured at 600 Mpa. On the other hand, at 800 MPa about 90%
of the total ß- lactoglobulins and about 50% of the α- lactalbumin was
denatured (Goyal et al., 2013).
The primary structure of proteins remains intact during HHP treatment in the range of 100 to 300 MPa, these changes are reversible, but pressures above 300 MPa can bring on irreversible denaturation of milk proteins. Changes in proteins can cause different functional characteristic or improve the organoleptic properties of HPP-treated dairy products (Ravash., et al 2022).
REFRENCES
EFFECT OF HHP ON MILK ENZYMES
High-pressure
applications can either activate or deactivate milk enzymes; occasionally, they
may even have no impact. However, the HPP effect is dependent on the process
conditions and the pressure intensity (Ravash et al., 2022). Enzymes can be
divided into two groups based on their effect on pressure. The primary
structure remains unaffected upon pressurization, while the secondary structure
may be affected at higher pressures. HPP affects the tertiary and quaternary
structures by modifying electrostatic, hydrophobic, and hydrogen bonds. Enzymes
can be divided into two groups: those that are activated at pressures of
100-500 MPa and those that are inactivated at pressures higher than 500 MPa in
combination with high temperatures. Indigenous enzymes in milk, such as lipase,
xanthine oxidase, lactoperoxidase, and γ-glutamyltransferase, are resistant to
pressures up to 400 MPa at 20-25°C (Nassar et al., 2016).
High
hydrostatic pressure treatment significantly impacts milk’s enzymes, when put
under high pressure, causing denaturation or deactivation of lactase and lipase
enzymes. Deactivated enzymes prevent undesirable changes in texture, flavor,
and fragrance, and delay spoiling in dairy products (Munir et al., 2020). Milk
enzymes, including lipase, xanthine oxidase, and lactoperoxidase, are resistant
to high pressures up to 400 MPa, while phosphatohexose isomerase, γ-glutamyl
Transferase, and alkaline phosphatase are partially or completely inactivated
at pressure 550, 630 and 800 MPa Respectively (Ravash et al., 2022).
EFFECT
ON MILK FAT
Relatively
few studies have examined the effect of HPP on milk fat, milk fat globules and
the Milk fat globule membrane (MFGM). Pressures less or equal 400 MPa did not
affect the mean diameter or the size distribution of milk fat globules, But
higher pressures between 400-800 MPa increased the former and broadened the
latter. Since no increase in products of lipolysis was detected, no damage to
the MFGM was thought to have occurred Under HP. Crystallization Of fat can be
accelerated, enforced, or initiated because of the shift in the phase
transition temperature caused by application of high pressure. The HPP-treated
cream had a higher solid fat content Than untreated cream, also with a maximum
effect At 200 MPa (Buchheim et al., 1996b). At pressure up to 200 MPa, the crystallization
and melting temperatures of milk fat were found to increase by 16.3°C and
15.5°C/100 MPa, respectively. However,
above 350 MPa there Is lower extent of milk fat crystallization due to reduced
crystal growth because of reduced molecular mobility at higher pressures. As a
consequence, high-pressure treatment reduced the ageing time of ice cream mixes
And aided the physical ripening of cream for butter Making . The fat globule
Size distribution and flow behaviour of pasteurized Liquid cream are not
significantly changed by HPP At 450 MPa and 25 °C for 15–30 min or 10 °C for 30
Min. Mean diameter of the milk fat globule remains unaffected after high
pressure treatment. Following, high pressure treatment, There is some
incorporation of whey proteins into Milk fat globule membrane (MFGM) but as
there is no increase in lipolysis (Nassar et al., 2016).
EFFECT
OF HPP ON MILK VITAMIN
Regarding
vitamins, HHP generally has a positive impact on their retention in milk. HHP
causes less degradation of heat-sensitive vitamins like vitamin C and B complex
vitamins. Consequently, milk treated with high hydrostatic pressure tends to
retain a higher nutritional value, making it a preferred choice for consumers
seeking products with preserved vitamin content (Lim et al., 2023). Studies have reported that in milk treated at
high pressure of 400 MPa (2.5MPa/sec For 30 min at 25°C) no significant loss of
B group Vitamins (Vit B1 and B2) were observed (Vandhana et al., 2020).
PACKAGING
FOOD TREATED WITH HPP
Packaging technology
for HPP involves different considerations, based on
whether a product is processed in-container
or packaged after processing. For batch in-container process flexible or partially rigid packaging is
best suited. On the other hand,
fluid products require
continuous or
semi-continuous systems, which
are aseptically packaged after
pressure treatment. The effectiveness of
HPP is greatly influenced by the
physical and mechanical properties
of the packaging
material. The packaging material must
be able to withstand the operating
pressures, have good
sealing properties and the
ability to prevent
quality deterioration during the application of pressure. At least one
interface of the package should be flexible enough to transmit the pressure.
Thus, rigid metal, glass or plastic containers cannot be used (Rastogi et al.,
2007). The most
common packaging materials used
for high pressure processed food are polypropylene (PP),
polyester tubes, polyethylene (PE) pouches,
and nylon cast
polypropylene pouches.
Plastic packaging materials
are the best suited
for HPP packaging application,
because of reversible
response to compression, flexibility and resiliency. The
headspace must be also minimized
while sealing the
package in order
to ensure efficient utilization
of the package as well as space within the pressure vessel. Packaging materials
for high pressure processing
must be flexible
to withstand a 15% increase in volume followed by a return to
original size, without
losing physical integrity, sealing
or barrier properties
(Nassar et al., 2016). The headspace must be minimized as much as
possible (Lambert, 2000) in order to control the deformation of packaging
materials and ensure efficient use of the
package and space
in the pressure
vessel. Sufficient headspace also minimizes the time taken to reach the
target pressure. Film barrier properties and
structural characteristics of
polymer based packaging material
were unaffected when subjected to
pressures of 400
MPa for 30
min at 25°C (Naik et al., 2013).
CONCLUSIONS
This
research has shown the potential of HPP treatment in preserving milk quality
for the dairy industry. This novel technology gives promising results in terms
of not only product safety and nutritional properties but also extending shelf
life significantly when compared to conventionally heat-treated milk.
HPP-treated milk had a storage shelf life beyond 60 days, with all microbial
testing meeting permitted safety levels. It had high stability for
physicochemical properties with consistent pH and acidity during the entire
storage. HPP treatment has successfully retained calcium, phosphorus,
magnesium, and zinc contents by 99.3, 99.4, 99.1, and 100%, respectively.
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