The activity of endogenous deteriorative enzymes together with microbial growth (with associated enzymatic activity) and/or other non-enzymatic (usually oxidative) reactions considerably shorten the ...shelf life of fruits and vegetable products. Thermal processing is commonly used by the food industry for enzyme and microbial inactivation and is generally effective in this regard. However, thermal processing may cause undesirable changes in product's sensory as well as nutritional attributes. Over the last 20 years, there has been a great deal of interest shown by both the food industry and academia in exploring alternative food processing technologies that use minimal heat and/or preservatives. One of the technologies that have been investigated in this context is high-pressure processing (HPP). This review deals with HPP focusing on its effectiveness for controlling quality-degrading enzymes in horticultural products. The scientific literature on the effects of HPP on plant enzymes, mechanism of action, and intrinsic and extrinsic factors that influence the effectiveness of HPP for controlling plant enzymes is critically reviewed. HPP inactivates vegetative microbial cells at ambient temperature conditions, resulting in a very high retention of the nutritional and sensory characteristics of the fresh product. Enzymes such as polyphenol oxidase (PPO), peroxidase (POD), and pectin methylesterase (PME) are highly resistant to HPP and are at most partially inactivated under commercially feasible conditions, although their sensitivity towards pressure depends on their origin as well as their environment. Polygalacturonase (PG) and lipoxygenase (LOX) on the other hand are relatively more pressure sensitive and can be substantially inactivated by HPP at commercially feasible conditions. The retention and activation of enzymes such as PME by HPP can be beneficially used for improving the texture and other quality attributes of processed horticultural products as well as for creating novel structures that are not feasible with thermal processing.
High pressure (HP) treatment has emerged as a novel, additive-free food preservation technology. It has been scientifically and commercially proven that HP can produce microbially safe and stable ...products with improved quality characteristics such as enhanced flavor and color. Recent studies have focused on the effects of HP on health attributes and allergenic potential of foodstuff to develop the next generation of convenience foods. This review provides an overview on the current knowledge of HP treatment to improve the extraction and bioavailability of bioactive compounds, to reduce allergenicity, to retain essential fatty acids, to reduce the salt content, and to reduce formation of processing contaminants. HP has shown encouraging potential to manipulate the functionality, extractability, allergenicity and bioavailability of micronutrients and components in a diverse variety of foods. However, the underlying principles and mechanisms are not yet fully understood and warrant further investigation. More studies are needed to optimize HP treatment conditions and develop a mechanistic understanding of the impacts of HP on different bioactive compounds in food products with health benefits. This can open the doors to new HP applications in the food industry.
•An overview on the current knowledge of HP treatment to improve healthy aspects•HP is a useful tool to improve extractability, and bioavailability of bioactives.•The potential of HP to reduce allergenicity and salt of food products was discussed.•HP ability to reduce formation of processing contaminants•HP principles and mechanisms are not yet fully understood.
During the last decades pulsed electric field (PEF) processing received considerable attention due to its potential to enhance food products or create alternatives to conventional methods in food ...processing. It is generally acknowledged that PEF processing can deliver safe and chill‐stable fruit juices with fresh‐like sensory and nutritional properties. Relatively low‐processing temperature and short residence times can achieve highly effective inactivation of microorganisms while retaining product quality. A first commercial application of PEF for preservation of fruit juices was launched in 2006 in the United States. Since then, industrial‐scale processing equipment for liquid and solid products were developed and, in Europe in 2009, an industrial juice preservation line was installed using 20 kV/cm pulses at 40 to 50 °C to extend the chill‐stability of fruit juices, including citrus juices and smoothies, from 6 to 21 d. The related PEF processing costs are in the range of US $0.02 to 0.03 per liter and are justified due to access to new markets and reduced return of spoiled product. However, despite its commercial success there are still many unknown factors associated with PEF processing of fruit and citrus juices and many conflicting reports in the literature. This literature review, therefore, aims to provide a comprehensive overview of the current scientific knowledge of PEF effects on microbial, enzymatic, nutritional, and sensory quality and stability of orange juices.
•High pressure activated/inactivated blueberry PPO depending on processing condition.•Thermal processing (60–76°C) had similar effect.•High pressure activated PPO by up to 6 times.•Thermal processing ...activated PPO by up to 3.5 times.•PPO inactivation without initial activation at temperature>76°C and pressure>500MPa.
Partially purified blueberry polyphenol oxidase (PPO) in Mcllvaine buffer (pH=3.6, typical pH of blueberry juice) was subjected to processing at isothermal–isobaric conditions at temperatures from 30 to 80°C and pressure from 0.1 to 700MPa. High pressure processing at 30–50°C at all pressures studied caused irreversible PPO activity increase with a maximum of 6.1 fold increase at 500MPa and 30°C. Treatments at mild pressure-mild temperature conditions (0.1–400MPa, 60°C) also caused up to 3 fold PPO activity increase. Initial activity increase followed by a decrease occurred at relatively high pressure-mild temperature (400–600MPa, 60°C) and mild pressure-high temperature (0.1–400MPa, 70–80°C) combinations. At temperatures higher than 76°C, monotonic decrease in PPO activity occurred at 0.1MPa and pressures higher than 500MPa. The activation/inactivation kinetics of the enzyme was successfully modelled assuming consecutive reactions in series with activation followed by inactivation.
The application of high pressure offers some interesting opportunities in the processing of muscle-based food products. It is well known that high-pressure processing can prolong the shelf life of ...meat products in addition to chilling but the pressure-labile nature of protein systems limits the commercial range of applications. High pressure can affect the texture and gel-forming properties of myofibrillar proteins and, hence, has been suggested as a physical and additive-free alternative to tenderize and soften or restructure meat and fish products. However, the rate and magnitude at which pressure and temperature effects take place in muscles are variable and depend on a number of circumstances and conditions that are still not precisely known. This review provides an overview of the current knowledge of the effects of high pressure on muscle tissue over a range of temperatures as it relates to meat texture, microstructure, color, enzymes, lipid oxidation, and pressure-induced gelation of myofibrillar proteins.
The objective of this work was to study the thermal and high pressure inactivation kinetics of polyphenol oxidase (PPO) and peroxidase (POD) in strawberry puree. PPO from two strawberry cultivars ...(‘Festival’ and ‘Aroma’) was found to be highly thermostable in strawberry puree with no significant inactivation even after 30
min treatment at 100
°C. In contrast, POD from the two cultivars displayed very high thermosensitivity with complete inactivation in less than 5
min at 70
°C. The thermal inactivation kinetics of strawberry POD was described by a biphasic model. The activation energies for the inactivation of the stable and the labile fractions were estimated to be 254.9 and 221.6
kJ/mol respectively. Combined high pressure–thermal treatment at pressures ranging from 100 to 690
MPa, temperatures ranging from 24 to 90
°C and treatment times between 5 and 15
min did not have significant effect on PPO while substantial inactivation of POD was observed. The inactivation kinetics of POD during combined high pressure–thermal processing was well described by first-order kinetics probably due to the inactivation of the labile fraction during the pre-heating and the compression phase.
The oxidative enzymes polyphenol oxidase and peroxidase cause the degradation of anthocyanins and other polyphenols in strawberry products, leading to discoloration and loss of antioxidant activity. In this work the thermal and high pressure inactivation of strawberry polyphenol oxidase and peroxidase was investigated so as to assess the suitability of high pressure processing as an alternative to thermal processing. Strawberry polyphenol oxidase was found to be highly resistant to both thermal and high pressure inactivation. Thus in order to maintain the quality of processed strawberry products, high pressure processing should be accompanied by additional measures such as exclusion of oxygen, refrigerated storage and the use of natural enzyme inhibitors.
The impact of high hydrostatic pressure and temperature on the stability of polyphenol oxidase (PPO) was studied in cloudy apple juice. Application of 200–500 MPa near room temperature or heat ...treatment at 45–55 °C at ambient pressure caused an increase of PPO activity of up to 65% in freshly squeezed apple juice. Combined pressure–temperature inactivation experiments with fully activated PPO (5 min treatment at 400 MPa and 20 °C) were carried out in the range of 0.1–700 MPa and 20–80 °C. Enzyme inactivation kinetics followed a 2.2 order reaction scheme at all pressure–temperature conditions tested. A polynomial model was successfully applied to describe the rate of PPO inactivation as a function of pressure and temperature and was used to construct a pressure–temperature isokinetic diagram. This diagram clearly showed synergistic effects of pressure and temperature on the inactivation of apple PPO at pressures above 300 MPa and antagonistic effects at lower pressures. Compared to ambient pressure conditions, temperatures required to inactivate PPO in apple juice were increased 10–15 °C at 100–300 MPa.
High pressure processing of fresh fruits is gaining popularity in the food industry because of its ability to inactivate microorganisms and some enzymes near room temperature with little impact on flavour or nutritional attributes of the food. However, quantitative data regarding the impact of process parameters on the target reaction are required to economically utilise this technology. This paper provides a mathematical model describing the combined effect of pressure, temperature and treatment time on the inactivation of PPO in cloudy apple juice.
The degradation kinetics of total anthocyanins in blueberry (Vaccinium myrtillus) juice were studied during thermal processing by treatment at selected temperatures (60−121 °C) and combined high ...pressure−temperature processing (100−700 MPa, 40−121 °C). Anthocyanin stability was also studied for several of these treatments during storage at 4, 25, and 40 °C. Both pressure and temperature increased d, the degradation rate of total anthocyanins in blueberry juice, meaning that at constant temperature, anthocyanins were more rapidly degraded with increasing pressure. For example, 32% degradation of anthocyanins was observed after 20 min heating at 100 °C and atmospheric pressure, whereas at 100 °C and 600 MPa, approximately 50% of total anthocyanins were lost. Degradation of anthocyanins was significantly accelerated with increasing storage temperatures. Combined pressure−temperature treatment of pasteurized juice led to a slightly faster degradation of total anthocyanins during storage compared to heat treatments at ambient pressure. Degradation of anthocyanins was best described by a 1.4th-order reaction at all conditions investigated. A mathematical model describing the degradation of blueberry anthocyanins in juice as a function of pressure, temperature, and treatment time is presented.
Extruded snack products were made from an oat fiber‐corn flour matrix fortified with 1.5% (w/w) curcuminoids (750 mg curcuminoids/100 g) to improve the solubility and stability of curcuminoids. The ...effects of extruder feed moisture content (21%, 28%, and 35%) and screw speed (200 and 300 rpm) on the extrusion parameters and physical properties of final snacks were investigated. Curcuminoids lost during extrusion and curcuminoids loss during subsequent drying of extrudates were analyzed, to separate the losses occurring in each unit process. Drying post extrusion (at 50 °C for 4 hr) was essential to obtain a crunchy shelf stable product (5% moisture). Curcuminoids loss during extrusion was from 17% to 84%, with high loss for the extrusion with low feed moisture content (21%). A further curcuminoids loss of 4% to 44% occurred during drying, with much higher loss for the extrudate with high moisture content. Total curcuminoids retained after extrusion and drying was 12% to 41% (59% to 88% loss), equivalent to 180 to 616 mg curcuminoids retained per 100 g snack, levels within recommended daily dose. Curcuminoids retained after drying was stable during 80 days of storage at 25 °C. The results highlighted the importance of understanding the impact of each unit process separately (for example, extrusion and drying) on the stability of curcuminoids for the development of healthier extruded snacks.
Practical Application
Extruded snacks products were developed by fortifying the snacks with oat fiber and curcuminoids in order to address the need for a healthy ready to eat food products. Some extrusion characteristics were selected to produce snack products which have favorable properties in terms of consumer acceptance.
Inactivation of Escherichia coli ATCC 11775 and Pseudomonas fluorescens ATCC 948 in UHT whole (4% fat) milk during thermal processing at 56–62 °C and pulsed electric field (PEF) processing at 30 or ...35 kV cm−1 at approximately 30, 40 or 50 °C was investigated. E. coli ATCC 11775 was more heat-resistant than P. fluorescens ATCC 948, but more susceptible to PEF processing. All inactivation kinetics showed strong deviations from log-linearity. Thus, a simplified logistic (log-decay) regression model was used to accurately predict thermal and PEF inactivation of E. coli ATCC 11775 and P. fluorescens ATCC 948 under various treatment conditions. This is a useful tool for identifying processing conditions to inactivate pathogenic and spoilage microorganisms in whole milk at sub-pasteurisation temperatures.
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