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High pressure processing has emerged as a versatile technology for food processor use to ensure food safety and preserve various heat sensitive nutrients and bioactive compounds. By carefully controlling pressure-thermal intensity, the treatment helps to reduce product thermal exposure while simultaneously achieving different treatment effects including pasteurization, sterilization, and shelf-life extension. This opinion paper summarizes scientific advances and future research needs in food process design and development of high pressure-based technologies. Research underway to develop continuous high pressure ultra-shear technology for formulating liquid beverages, sauces, and nano emulsions. Emerging application of high-pressure technology include its use as extraction tool for separating bioactive compounds from various food waste, and as a hyperbaric storage method for reducing energy use during refrigeration storage of foods.

The aim of the presented study was to determine the ability of the high pressure processing (HPP) for extraction of bioactive compounds from black carrot pomace and to optimize treatment conditions (pressure, temperature, processing time) for obtaining the maximum yield of bioactive compounds. Experiments were conducted using pilot scale high pressure food processors and water as the extraction solution. A set of response surface analysis mathematical models were developed and validated for the extraction of bioactive compounds of black carrot pomace, considering total monomeric anthocyanin contents (TMA), total phenolic compounds (TPC) and antioxidant activity (AA). Quality attributes such as total color difference (Delta E*) and polymeric color ratio (PCR) of the samples were also evaluated. The validation results showed that the error values of the obtained models were lower than 10%, which means acceptable error value in modelling study. Combined pressure-thermal treatment at 266.6 MPa, 78.3 degrees C for 13.6 min was identified as the optimal process condition for maximum extraction of bioactive compounds.

Experiments were conducted to investigate osmotic dehydration of ginger slices suspended in three different osmotic agents at 0.1–600 MPa and 40 °C for various pressure holding times. A Weibull distribution mathematical model was employed to predict the kinetics of moisture and solute transport during osmotic dehydration of ginger. Increased process pressure accelerated the water loss and solid gain and removed significant amount of water within a shorter time period. The effective moisture diffusivity values for glucose, fructose, and sucrose at 0.1 MPa and 40 °C were 0.322 × 10−9, 0.362 × 10−9 and 0.396 × 10−9 m2/s respectively. Pressure treatment at 600 MPa increased these values by approximately by 11–12 folds (3.725 × 10−9, 4.027 × 10−9 and 4.293 × 10−9 m2/s respectively). Among the osmotic agents tested, solute diffusivity was maximum in glucose followed by fructose and sucrose, whereas the moisture diffusivity was greatest in sucrose and lowest in glucose.

A study assessed combined pressure-thermal treatment effect on quality attributes of selected acidified vegetables (banana pepper, red beets and green asparagus) over 30 days storage at 25 °C. Vegetables were acidified by suspending them in pickling liquid either through thermal blanching or 8 h storage at ambient temperature. Subsequently, samples were pressure treated in a pilot scale high pressure processor at 600 MPa, 45° or 65 °C for 5 min and stored at ambient temperature for 30 days. Quality analyses included texture, enzyme activity, color, pH and °Brix. Processed products remained stable during storage (pH Industrial relevance The research documented the quality changes in selected acidified vegetable pickles subjected to various pressure-thermal treatments. By reducing thermal impact, high pressure treatment in combination with modest heat can help preserve quality attributes of acidified vegetable pickles with the extended shelf life. The knowledge from this study could help the food processors in deciding relevance of high pressure processing for industrial manufacturing of acidified low-acid shelf-stable vegetable matrices.

The mass transfer kinetics during osmotic dehydration of granny smith apple slices in 60 Brix fructose and sucrose solution was studied at atmospheric pressure and at elevated pressure of 2...

High pressure based technologies are of interest, as they enable the food processors to inactivate harmful and spoilage organisms, extend product shelf life, while having minimal impact on nutrients and fresh like quality attributes of foods. However, simultaneous application of pressure-thermal treatment is required for spore inactivation. Pressure in combination with heat can have synergistic, antagonistic or additive effects on various physical, biochemical and biological reactions in food matrices. It is also important to characterize the engineering properties of foods as influenced by pressure-heat combinations and model the extent of process non-uniformity within processed volume. Suitably controlling the pressure-thermal intensity enables the processors to manufacture various pasteurized, extended shelf-life, and shelf-stable foods. Therefore, this chapter summarizes basic principles associated with food process design and development of high-pressure based technologies, factors governing food safety and quality, and highlight relevant industrial applications.

Understanding the inactivation kinetics of bacterial spores during combined pressure-thermal processing is essential for process design. The knowledge on the influence of pH and water activity (aw) during combined pressure-thermal treatment is limited. Experiments were conducted using Bacillus cereus spores suspended in citrate-phosphate buffers, adjusted to different levels of pH (3.8–7.3) and aw (0.80–0.99). Spores were then treated with a pressure-heat combination (600 MPa, 70 °C) using a laboratory-scale high-pressure kinetic tester. Linear regression and Weibull models were used to fit the experimental data. The kinetic parameters of the spores inactivation estimated from the models were plotted as a function of pH and aw. Results showed that the inactivation kinetic curves were characterized by tailing, particularly at low aw levels. The log reduction of B. cereus spores decreased with the decrease of aw. During pressure-thermal treatment, the changes in acidity values for a given water activity have limited influence on decimal reduction values of the spores. Study findings will be helpful for designing pressure-thermal processes to produce microbially safe products with varying water activity and acidity levels.

Producing a thermally sterilized egg-based product with increased shelf life without losing the sensory and nutritional properties of the freshly prepared product is challenging. Until recently, all commercial shelf-stable egg-based products were sterilized using conventional thermal processing; however, this heat treatment was problematic as quality attributes of the product were negatively affected. Combining high pressure with high temperature is a potential alternative to retorting for the production of shelf-stable egg-based products. This review discusses the challenges of high pressure thermal sterilization as an alternative processing method of producing shelf-stable egg products. Attention is given to product improvement in terms of overall quality through modification of ingredients, formulation, processing and packaging, offering the industry a practical way to produce egg-based products with increased shelf life and appealing quality to the consumer.

A study was conducted to evaluate the efficacy of various combinations of pressure and thermal treatments in preserving textural quality of selected foods. Carrot, zucchini, apricot, red radish, and jicama were used as test samples. Pressure-assisted thermal processing (PATP; 600 MPa, 105 °C), high-pressure processing (HPP; 600 MPa, 25 °C), and thermal processing (TP; 105 °C, 0.1 MPa) experiments were conducted. Role of pressure (600 MPa) in preserving product quality while simultaneously (PATP) or sequentially (HPP-TP) exposed to elevated process temperature (105 °C) was also compared. Instrumental puncture, shear force, color and sensory analyses were utilized to compare the influence of the various process treatments. A crunchiness index (CI), relating product puncture force and stiffness, was able to characterize the severity of the process treatments on various products tested. Among the treatments, TP was the worst at retaining texture, but HPP-TP improved texture retention. In comparison to TP alone, PATP better retained texture and color. Jicama was least influenced by the treatments as compared to products tested. Process treatments investigated degraded the textural quality of zucchini and apricot. Instrumental CI results were also in agreement with the sensory data of carrot, red radish and jicama samples.

The effect of high-pressure processing on texture and drying behavior of pineapple slices was investigated. Pineapple slices were high pressure processed at 50, 100, 300, 500 and 700 MPa at 25C for 10 min. The control, hot water-blanched and high-pressure processed samples were then dehydrated at 70C. Application of high pressure reduced the sample hardness, springiness and chewiness while it had no significant effect on cohesiveness of pineapple. Elevated pressure treatment (�500 MPa) reduced drying time more effectively than for the other pretreated samples. Experimental dehydration data were empirically fitted using six thin-layer drying models. Among the models tested, logarithmic model best described the drying behavior of pineapple slices. The effective moisture diffusivity was found to increase with an increase in the level of pressure up to 500 MPa, and the samples processed at 500 and 700 MPa had higher diffusivity values than blanched samples. PRACTICAL APPLICATIONS This work shows that high-pressure blanching of pineapple can be an alternative for hot water blanching, before dehydration. The results may find application in development of quality snack food from pineapple fruits.

Experiments were conducted to evaluate the feasibility of using high-pressure processing as an alternate for hot-water blanching of peach slices. Peach slices were pressure processed at various combinations of pressures (50–700 MPa) at 25°C with and without citric acid for two holding times (5 and 10 min). Pressure treatment (>300 MPa), in combination with citric acid (1–1.2%), was an effective method to inactivatepeach polyphenoloxidase enzymes. Pressure-treated peach slices, with and without citric acid, were subsequently dehydrated in a cabinet dryer at 70°C. Pressure treatment enhanced the drying rate and reduced the drying time. Logarithmic model satisfactorily described the drying behavior of peach slices. Pressure-processed samples had higher moisture diffusivity than control samples. The results reveals that high-pressure processing of peach fruits suspended in citric acid medium can be used as potential alternative for hot water blanching.

High pressure processing (HPP) of foods offers a commercially viable and practical alternative to heat processing by allowing food processors to pasteurize foods at or near room temperature. Pressure in combination with moderate temperature also seems to be a promising approach for producing shelf-stable foods. This paper outlines research needs for further advancement of high pressure processing technology. Kinetic models are needed for describing bacterial inactivation under combined pressure-thermal conditions and for microbial process evaluation. Further, identification of suitable surrogate organisms are needed for use as indicator organisms and for process validation studies. More research is needed to evaluate process uniformity at elevated pressure-thermal conditions to facilitate successful introduction of low-acid shelf-stable foods. Combinations of non-thermal technologies with high pressure could reduce the severity of the process pressure requirement. Likewise, processing equipment requires improvements in reliability and line-speed to compete with heat pasteurization lines. More studies are also needed to document the changes in animal and vegetable tissue and nutrient content during pressure processing, from types of packaging, and from storage.

The effect of various physical and chemical pretreatments such as pressure (100–400 MPa), temperature (50–70 °C), calcium chloride (0.5–1.5% w/v), and their combinations on carrot texture was studied after pressure-assisted thermal processing (PATP) and thermal processing. Untreated PATP and thermally processed samples without any pretreatment served as controls. Individual pretreatments were effective to a limited extent in improving the product quality. Pressure (200 MPa), heat (60 °C) and calcium chloride (1.0%) pretreatments increased product hardness by 1.2, 2.0 and 2.4 times after PATP and 2.7, 3.6 and 2.4 times, respectively, after thermal processing. Combined pretreatments increased the hardness of the samples by 9.16 times (from 14.08 to 129.07 N) and 13.22 times (from 4.36 to 57.63 N), respectively, in comparison to untreated PATP or thermally processed samples. The calcium content of the samples was found to have a positive influence in preserving hardness. The microstructure analysis of PATP carrots indicated that the combined high pressure, heat, and calcium pretreatments better preserved cell structure. This combined pretreatment process could serve as an effective tool in preserving the quality of PATP as well as thermally processed carrot.

During high pressure processing, the prepackaged food material is pasteurized or sterilized by subjecting it to combined pressure-thermal treatment of different intensity. This chapter summarizes the impact of pressure-thermal treatment on moisture and gas barrier properties, seal and mechanical strength, as well as migration characteristics of the packaging polymer. Packaging also play important role in preserving quality of pressure treated foods during extended storage life. Some of the recommended future research needs in the development of novel packaging material for high pressure processing are summarized.

Thermal conductivity ( k ) of selected liquid foods during high- pressure processing (HPP) was studied using a line heat source probe. The probe was calibrated using distilled water and probe specific calibration factors were developed by comparing experimental data against published data from National Institute of Standards and Technology (NIST) for water. k of commercially available apple juice, canola oil, clarified butter, honey and high fructose corn syrup (HFCS) were then determined using a custom made high pressure experimental setup for various pressures (0.1, 100, 300, 500 and 700 MPa) at 25 °C. Results indicated that material k increased linearly with increasing pressures up to 700 MPa. Water and water-like substances (apple juice) were found to have the highest k values (up to 0.82 W/m °C at 700 MPa), while fatty foods such as canola oil and clarified butter had the lowest (0.29–0.4 W/m °C, respectively at 700 MPa) values. Honey and HFCS had intermediate values. The combined uncertainty (including Type A and Type B) in the measurement of k values of various liquid foods ranged from 0.6% (canola oil) to 3.8% (HFCS).

Different methods for improving texture profile and water retention of scrambled egg patties after high-pressure high-temperature (HPHT) treatment were evaluated as part of a feasibility study for the development of shelf-stable egg products. Four formulations, a basic one, 2 with xanthan gum, 1 with cheese, were compared after HPHT treatment by analyzing texture profile and degree of syneresis. The effects of water addition of 0% to 15%, 3 levels of vacuum packaging, 4 preheating rates, and 2 HPHT conditions (700 MPa/105 °C/5 min and 700 MPa/121 °C/3 min) on texture and water retention of egg patties were also compared for selected formulations. Patties reformulated with xanthan gum and cheese resulted in at least a 30% reduction in hardness, cohesiveness, and water loss. Use of low vacuum packaging in less porous patties modified with xanthan gum maintained original texture values after 700 MPa/105 °C/5 min. Addition of water into the defrosted structure increased water holding capacity and maintained hardness within its standard value after pressurization at 105 °C and 121 °C. Most texture descriptors and syneresis did not change significantly with preheating rates after HPHT treatment. Tested mechanisms for texture and water retention improvement of HPHT treated patties can contribute to meeting quality requirements not fulfilled by conventional thermal processing for the development of shelf-stable scrambled egg products.

This paper highlights some of the common problems and pitfalls that may be encountered by a researcher conducting high-pressure microbial inactivation studies. One of the unique advantages of high-pressure food processing in comparison to thermal processing is that pressure acts uniformly and instantaneously throughout the mass of the food. On the other hand, increase in sample temperature, due to pressurization, can lead to process non-uniformity issues during high-pressure processing (HHP). Differences in equipment heat transfer characteristics and inadequate reporting of experimental methodologies may hinder independent verification of results between laboratories. Knowledge of thermal history and controlling thermal effects is critical for conducting high-pressure microbial inactivation studies. Approaches that may aid in meaningful comparison of results obtained among various laboratories are provided.

High pressure processing (HPP) holds the potential for preserving foods by a combination of elevated pressures (up to 900 MPa or approximately 9000 atmospheres) and moderate temperatures (up to 110 °C) over a short period of time. Although high pressure processed salads are currently unavailable, HPP has been used as an alternative to heat pasteurization for processing ready meals in North America, Europe and some Asian countries. The effects of HPP on selected ready meals, salads dressings, dips, and sauces are reviewed. Aspects covered include combined pressure-thermal effects on microbial and enzyme inactivation. Pressures up to 600 MPa can inactivate yeasts, moulds and most vegetative bacteria including pathogens. Meanwhile, HPP has minimal effect on compounds with low molecular weight, such as flavor compounds and vitamins, and its influence on color is product dependent. This varies between a full retention of the fresh color and color change similar to thermally processed foods.

White-brined cheeses were subjected to high-pressure processing (HPP) at 50, 100, 200, and 400 MPa at 22 °C for 5 and 15 min and ripened in brine for 60 d. The effects of pressure treatment on the chemical, textural, microstructural, and color were determined. HPP did not affect moisture, protein, and fat contents of cheeses. Similar microstructures were obtained for unpressurized cheese and pressurized cheeses at 50 and 100 MPa, whereas a denser and continuous structure was obtained for pressurized cheeses at 200 and 400 MPa. These microstructural changes exhibited a good correlation with textural changes. The 200 and 400 MPa treatments resulted in significantly softer, less springy, less gummy, and less chewy cheese. Finally, marked differences were obtained in a* and b* values at higher pressure levels for longer pressure-holding time and were also supported by ΔE* values. The cheese became more greenish and yellowish with the increase in pressure level. Practical Application: The quality of cheese is the very important to the consumers. This study documented the pressure-induced changes in selected quality attributes of semisoft and brine-salted cheese. The results can help the food processors to have knowledge of the process parameters resulting in quality changes and to identify optimal process parameters for preserving pressure-treated cheeses.

The effects of high-pressure (33, 400 and 700 MPa for 3 min at 24 and 55°C) and irradiation (2 and 5 kGy) pre-treatments on hydration behavior of navy beans were studied by soaking the treated beans in water (1:2, w/w) at 24 and 55°C. Beans hydrated at 55°C and allowed to cool by natural convection served as the control. Treating beans under moderate pressure (33 MPa) resulted in high initial moisture uptake (0.59 to 1.02 kg/kg dry mass) and reduced loss of soluble materials. The final moisture content after three hours of soaking was the highest in irradiated beans (5 kGy) followed by HPP (33 MPa; 3 min; 55°C). Within the experimental range of the study, Peleg’s model was found to satisfactorily describe the rate of water absorption of navy beans. Peleg's constant K1 had an inverse correlation with soaking temperature whereas K2 increased with increases in temperature and pressure.