Opportunities and Challenges in High Pressure Processing of Foods

Inactivation of Shiga Toxin-Producing Escherichia coli and Listeria monocytogenes within Plant versus Beef Burgers in Response to High Pressure Processing

ABSTRACT

We evaluated high pressure processing to lower levels of Shiga toxin-producing Escherichia coli (STEC) and Listeria monocytogenes inoculated into samples of plant or beef burgers. Multistrain cocktails of STEC and L. monocytogenes were separately inoculated (∼7.0 log CFU/g) into plant burgers or ground beef. Refrigerated (i.e., 4°C) or frozen (i.e., -20°C) samples (25 g each) were subsequently exposed to 350 MPa for up to 9 or 18 min or 600 MPa for up to 4.5 or 12 min. When refrigerated plant or beef burger samples were treated at 350 MPa for up to 9 min, levels of STEC were reduced by ca. 0.7 to 1.3 log CFU/g. However, when refrigerated plant or beef burger samples were treated at 350 MPa for up to 9 min, levels of L. monocytogenes remained relatively unchanged (ca. ≤0.3-log CFU/g decrease) in plant burger samples but were reduced by ca. 0.3 to 2.0 log CFU/g in ground beef. When refrigerated plant or beef burger samples were treated at 600 MPa for up to 4.5 min, levels of STEC and L. monocytogenes were reduced by ca. 0.7 to 4.1 and ca. 0.3 to 5.6 log CFU/g, respectively. Similarly, when frozen plant and beef burger samples were treated at 350 MPa up to 18 min, reductions of ca. 1.7 to 3.6 and ca. 0.6 to 3.6 log CFU/g in STEC and L. monocytogenes numbers, respectively, were observed. Exposure of frozen plant or beef burger samples to 600 MPa for up to 12 min resulted in reductions of ca. 2.4 to 4.4 and ca. 1.8 to 3.4 log CFU/g in levels of STEC and L. monocytogenes, respectively. Via empirical observation, pressurization did not adversely affect the color of plant burger samples, whereas appreciable changes in color were observed in pressurized ground beef. These data confirm that time and pressure levels already validated for control of STEC and L. monocytogenes in ground beef will likely be equally effective toward these same pathogens in plant burgers without causing untoward effects on product color.

HIGHLIGHTS

Table Olives: An Overview on Effects of Processing on Nutritional and Sensory Quality

Table olives are a pickled food product obtained by a partial/total debittering and subsequent fermentation of drupes. Their peculiar sensory properties have led to a their widespread use, especially in Europe, as an appetizer or an ingredient for culinary use. The most relevant literature of the last twenty years has been analyzed in this review with the aim of giving an up-to-date overview of the processing and storage effects on the nutritional and sensory properties of table olives. Analysis of the literature has revealed that the nutritional properties of table olives are mainly influenced by the processing method used, even if preharvest-factors such as irrigation and fruit ripening stage may have a certain weight. Data revealed that the nutritional value of table olives depends mostly on the balanced profile of polyunsaturated and monounsaturated fatty acids and the contents of health-promoting phenolic compounds, which are best retained in natural table olives. Studies on the use of low salt brines and of selected starter cultures have shown the possibility of producing table olives with an improved nutritional profile. Sensory characteristics are mostly process-dependent, and a relevant contribute is achieved by starters, not only for reducing the bitterness of fruits, but also for imparting new and typical taste to table olives. Findings reported in this review confirm, in conclusion, that table olives surely constitute an important food source for their balanced nutritional profile and unique sensory characteristics.

Extraction of bioactive compounds from purple corn using emerging technologies: A review

The increase in the use of bioactive compounds from purple corn in the food and pharmaceutical industries has led to the investigation of nonconventional extraction technologies that allow one to obtain more of these compounds. In this context, nonconventional techniques, known as emerging technologies, use more efficient processes that are safe for the environment, in addition to obtaining products with better functional characteristics as compared to those obtained by conventional technologies. This review aims to provide information on different nonconventional techniques used in the extraction of bioactive compounds from purple corn.

Pressure Induced Structural Changes of Proteins Affecting the Ice Nucleation Temperature of Pork Loins

This study investigated the effects of pressure-mediated protein changes on the ice nucleation temperature of pork loins. To variate chemical state of meat proteins, pork loin was pressurized at varying pressure levels (100–500 MPa) for 3 min, and moisture content, expressible moisture (EM) and differential scanning calorimetry (DSC) were analyzed. Although, all treatments showed similar moisture content, EM and degree of protein unfolding of pork loin showed different features as of 300 MPa. At moderate pressure treatments (100–200 MPa), all protein fractions were detected in DSC experiments, and pork loin had lower EM than control (p<0.05). Meanwhile, myosin and actin of pork loin treated at greater than 300 MPa were completely unfolded, and the treatments showed high EM compared to control (p<0.05). Unfolding of meat proteins was a factor suppressing ice nucleation, and the ice nucleation temperature tended to decrease with increasing applied pressure level. The ice nucleation characteristics of pressurized pork loin exhibited a potential application in freezing storage of pressurized meat with less tissue damage comparing to freeze fresh meat, and further exploration regarding the quality change after freezing of fresh and pressurized meat was warranted.

Effects of high hydrostatic pressure and soaking solution on proximate composition, polyphenols, anthocyanins, β-carotene, and antioxidant activity of white, orange, and purple fleshed sweet potato flour

Effects of high hydrostatic pressure (100, 200, and 400 MPa) and soaking solution (citric acid, calcium chloride, ascorbic acid, and distilled water) on proximate composition, polyphenols, anthocyanins, β-carotene, and antioxidant activity of white, orange, and purple fleshed sweet potato flour were investigated. Total polyphenol content was increased in sweet potato flour of Jishu 98 (white) at 200 MPa with ascorbic acid and Pushu 32 (orange) at 0.1 MPa with ascorbic acid treatment (0.51 and 0.83 mg gallic acid equivalent/g dry weight, respectively), but was decreased in Xuzishu No. 3 (purple) in both high hydrostatic pressure and soaking solution treatments. Total anthocyanin content was declined in all treated sweet potato flour. Nevertheless, high hydrostatic pressure with citric acid, calcium chloride, and distilled water significantly increased the β-carotene content in Pushu 32. Correlation analysis between total polyphenol content, total anthocyanin content, and antioxidant activity suggested that polyphenols are the most pivotal antioxidant in sweet potato flour. High hydrostatic pressure and soaking solution treated sweet potato flour could be potentially utilized in food with acceptable nutritional values.

Effect of High-Pressure Processing (HPP) on the Fatty Acid Profile of Different Sized Ragworms (Hediste diversicolor) Cultured in an Integrated Multi-Trophic Aquaculture (IMTA) System

Ragworms (Hediste diversicolor) cultured under integrated multi-trophic aquaculture (IMTA) conditions display an improved fatty acids (FA) profile than conspecifics from the wild, thus being more suitable for maturation diets of marine fish and shrimp. Nonetheless, their use may represent a potential pathway for pathogens. The objective of the present study was to determine if high-pressure processing (HPP), as an approach to safeguard microbiological safety, could promote significant shifts on the FA profiles of different sized ragworms. An analysis of similarities (ANOSIM) revealed the existence of significant differences in the FA profile and lipid quality indexes (atherogenicity (AI), thrombogenicity (TI) and polyene (PI)) of control and HPP treated ragworms of all tested sizes (small, medium and large). Saturated (SFA) and monounsaturated FA (MUFA) increased after HPP, while polyunsaturated FA (PUFA; FA with 2 or 3 double bonds) and highly unsaturated FA (HUFA; FA with ≥ 4 double bonds) decreased. The amount of docosahexaenoic acid (DHA) in polychaetes exposed to HPP decreased an average of 25%, when compared with the levels recorded in control groups. The values of PI significantly decreased after HPP, while those of AI and TI displayed a significant increase. Despite the shifts in the FA profile of ragworms exposed to HPP, these still display a superior profile to that of wild specimens, namely the presence of DHA. Therefore, HPP can be considered as a suitable approach to safeguard the biosecurity of cultured polychaetes, without compromising their nutritional value, and support the principles of circular economy through the use of IMTA.

Texture Modification Technologies and Their Opportunities for the Production of Dysphagia Foods: A Review

Dysphagia or swallowing difficulty is a common morbidity experienced by those who have suffered a stroke or those undergone such treatments as head and neck surgeries. Dysphagic patients require special foods that are easier to swallow. Various technologies, including high-pressure processing, high-hydrodynamic pressure processing, pulsed electric field treatment, plasma processing, ultrasound-assisted processing, and irradiation have been applied to modify food texture to make it more suitable for such patients. This review surveys the applications of these technologies for food texture modification of products made of meat, rice, starch, and carbohydrates, as well as fruits and vegetables. The review also attempts to categorize, via the use of such key characteristics as hardness and viscosity, texture-modified foods into various dysphagia diet levels. Current and future trends of dysphagia food production, including the use of three-dimensional food printing to reduce the design and fabrication time, to enhance the sensory characteristics, as well as to create visually attractive foods, are also mentioned.

Combined Osmotic and Membrane Distillation for Concentration of Anthocyanin from Muscadine Pomace

Bioactive anthocyanins from aqueous extracts of muscadine grape pomace were concentrated using osmotic distillation (OD) and direct contact membrane distillation (DCMD) using polypropylene (PP) and poly(ethylene chlorotrifluoroethylene) (ECTFE) membranes. The driving force for OD is created by using a high concentration brine solution while the driving force for DCMD is generated by elevating the feed temperature relative to the permeate temperature. The brine concentration used was 4 M. The lowest fluxes were obtained for OD. Given the temperature sensitive nature of anthocyanins, the maximum temperature difference during DCMD was limited to 30 °C. The feed temperature was 40 °C and the permeate at 10 °C. Consequently, the maximum flux during DCMD was also limited. A combination of OD and DCMD was found to give the highest fluxes. High-performance liquid chromatography (HPLC) and HPLC-electrospray mass spectrometry were used to identify and quantify anthocyanins, cyanidin-3,5-O-diglucoside, delphinidin-3,5-O-diglucoside, petunidin-3,5-O-diglucoside, peonidin-3,5-O-diglucoside, and malvidin-3,5-O-diglucoside. The results obtained here suggest that, though water fluxes for DI water feed streams for PP and ECTFE membrane were similar, the fluxes obtained for the two membranes when using muscadine pomace extracts were different. Concentration factors of close to 3 was obtained for anthocyanins. Membranes also showed slightly different performance in the concentration process. Membrane surfaces were analyzed using scanning electron microscopy and Fourier-transformed infrared spectroscopy. The results suggest that adsorption of these anthocyanins on the membrane surface lead to performance differences. In an actual operation, selection of an appropriate membrane and regeneration of the membrane will be important for optimized performance. PRACTICAL APPLICATIONS: Anthocyanins are valuable therapeutic compounds, which are found in the solid residue left following fruit juice pressing. However, recovery and concentration of these therapeutic compounds remains challenging due to their stability. Here, a novel membrane-based unit operation has been investigated in order to concentrate the anthocyanins that have been extracted into aqueous solutions. The unit operation investigated here use mild processing conditions. Insights into the factors that need to be considered when optimizing of the unit operation for commercialization are discussed.

Evaluation of Hydrostatic High Pressure and Cold Storage Parameters for the Reduction of Campylobacter jejuni in Chicken Livers

HIGHLIGHTS

Effects of carrot incorporation and high hydrostatic pressure processing on fresh cheese: Antilisterial activity, carotenoid degradation, and sensory characteristics

This study was carried out to evaluate the antilisterial activity of carrot, and the impact of its incorporation on the carotenoid content in Minas Frescal cheese, combined or not with high hydrostatic pressure processing, as an alternative for the development of healthier fresh cheese free of synthetic preservatives. Cheeses were manufactured with milk added with carrot incorporation (0, 3, and 6%) and pressurized (0; 250 and 500 MPa/10 min). Total carotenoid content, α-carotene, β-carotene, lutein, consumer acceptance, and sensory characteristics were determined one day after the manufacture while Listeria innocua enumeration was evaluated up to 22 days of storage at 8 ℃. The results showed that although a decrease of over 7 log CFU g^-1 in L. innocua counts was observed immediately after fresh cheese processing at 500 MPa/10 min, inactivation was not complete, as the growth of this nonpathogen surrogate during storage was observed. The addition of 6% carrot had a slight bacteriostatic effect, verified on the 15th day of storage, particularly in pressurized cheeses. On the other hand, high pressure treatment at 500 MPa/10 min increased carotenoids degradation in cheeses. Although pressurized cheeses were characterized as "rubbery," high hydrostatic pressure had no significant effect on consumer acceptance.

A New High Hydrostatic Pressure Process to Assure the Microbial Safety of Human Milk While Preserving the Biological Activity of Its Main Components

Background: The main process used to pasteurize human milk is the low-temperature, long-time Holder method. More recently, the high-temperature, short-time method has been investigated. Both processes lead to the appropriate inactivation of vegetative bacterial forms but are ineffective against bacterial spores. Research Aims/Questions: We aimed to accomplish two main objectives: inactivation of all pathogens, including spores; and preservation of the activity of milk components. Design/Methods: Recently, a novel high-hydrostatic pressure process has been developed by HPBioTECH. Using the same raw human milk samples, we compared the effects of this method with those of the Holder method on vegetative and spore forms of pathogens and on bioactive components (lipase activity, immunoproteins). Results: Two main microbial strains were selected: Staphylococcus aureus (as a reference for vegetative forms) and Bacillus cereus (as a reference for spores). Use of the high-hydrostatic pressure process led to microbial decontamination of 6 log for both S. aureus and B. cereus. Additionally, the bioactivity of the main components of human milk was preserved, with activities of lipase, α-lactalbumin, casein, lysozyme, lactoferrin, and sIgA of ~80, 96-99, 98-100, 95-100, 93-97, and 63-64%, respectively. Conclusions: Use of this novel high-hydrostatic pressure process to generate microbiologically safe human milk may provide important benefits for preterm infants, including improved assimilation of human milk (leading increased weight gain) and improved resistance to infections. Because 10% of all human milk collected is contaminated by B. cereus, use of this method will also prevent waste.

Consumers' preferences for freezing of meat to prevent toxoplasmosis- A stated preference approach

Consumption of raw or undercooked meat increases the risk of infection with Toxoplasma gondii. Freezing meat products can eliminate this risk. Freezing of meat may affect consumers' valuation of meat products in two different ways: it may be valued positively because of increased food safety or valued negatively because of (perceived) loss of quality. In a Discrete Choice Experiment on four different meat products we studied the difference in willingness to pay for frozen and non-frozen meat products in the Netherlands. Analyses revealed that most Dutch consumer groups prefer non-frozen meat. Price was important in consumer decisions, whereas the meat being frozen appeared to play a minor role in the decision to purchase meat products. Even though it may seem obvious that people would prefer safe food to unsafe food, in a context where consumers presume food being safe, many consumers appear unwilling to pay for freezing of meat as additional measure to reduce the risk of food borne infections such as toxoplasmosis.

Long-Term Effect on Bioactive Components and Antioxidant Activity of Thermal and High-Pressure Pasteurization of Orange Juice

The long-term effect of thermal pasteurization (TP) and high-pressure processing (HPP) of orange juices stored under refrigeration, on the bioactive components and antioxidant activity, was compared. Total phenolic content (TPC), flavonoid, anthocyanin, and carotenoid contents, the individual content of major phenolic components, and the antioxidant activity, were evaluated in TP- and HPP-treated juices over a 36-day period. At day 0, no significant differences in TPC, and a decrease in carotenoid content after both treatments, were observed. TP caused a decrease of flavonoid and anthocyanin contents, while HPP increased flavonoid content. Three major phenolic components were identified: apigenin-6,8-di-C-glucoside, naringenin-7-O-rutinoside, and hesperetin-7-O-rutinoside, the latter increasing ca. 45% immediately after HPP. During storage, a decrease in TPC, and in the anthocyanin and carotenoid contents of both treated juices was observed, with higher anthocyanin and phenolic contents in HPP juices. A significant increase of hesperetin-7-O-rutinoside content was observed in HPP juice. Both treatments caused a decrease (26% and 13%, respectively) of antioxidant activity. Most of the kinetic profiles followed zero-order patterns, with HPP juices showing a considerably higher half-life than TP ones. These results clearly demonstrate the advantages of HPP for orange juice preservation allowing, also, their nutritional benefits to be enhanced by increasing the content of some bioactive components.

Nutrient evaluation of a pork by-product and its use as environmental enrichment for managed large exotic cats

North American zoological institutions typically feed ground raw meat diets to large exotic cats. These diets typically are nutritionally complete, but lack physical properties characteristic of whole prey. Lack of mastication and prey manipulation may contribute to behavioral and health challenges. Pork by-products may provide environmental enrichment to mitigate these challenges. The objectives of this study were to evaluate a pig head for nutritional composition and to determine if a pig head was biologically relevant environmental enrichment for managed large exotic cats. Pig heads consisted of: DM: 48.5%; OM: 60.7%; CP: 38.4%; fat: 22.0%; CF: 13.5%; TDF: 3.4%; GE: 4.1 kcal/g DM. Five individually housed exotic cats (Panthera tigris tigris, Panthera tigris altaica (n = 2), Panthera tigris jacksoni, Panthera leo) were observed in 2-h blocks, 24-h before pig head introduction (Baseline), at time of pig head introduction (Enrichment) and immediately after the pig head was removed (Post Enrichment) via instantaneous scan sampling for 4 consecutive weeks. Active behaviors were 55.7% higher on Enrichment compared to Baseline days, and 26.4% higher compared to Post Enrichment days (p<0.0001). Active behaviors were 39.8% higher on Post Enrichment compared to Baseline days (p<0.0001). Total active behaviors were highest (p<0.0001) in week 3 and lowest (p<0.0001) in week 4 with differences as high as 64.5% seen among weeks. In conclusion, pig heads have potential to provide nutrient dense enrichment to large exotic cats, and employing a pig head as environmental enrichment increased active behaviors and did not lose novelty.

Effect of various food processing and handling methods on preservation of natural antioxidants in fruits and vegetables

Bioactive compounds from plant sources are generally categorized as natural antioxidants with well-known health benefits. The health-promoting characteristics of natural antioxidants include anti-inflammatory, anti-diabetic, and hepatic effects as well as free radical scavenging. Herein, a comprehensive and comparative review are presented about the effects of conventional (thermal and mechanical) and relatively new (non-thermal) processing methods on phytochemicals and discussed the importance of implementing the use of those methods that could be of very helpful retaining the quality of the bioactive compounds in plant-based foods. Plant-based foods rich in phenolics, vitamin C, carotenoids, and other compounds undergo a range of processing operations before they are consumed. Most of these methods involve thermal treatments of fruits, stems, leaves, and roots. These techniques have varying effects on bioactive compounds and their activities, and the magnitude of these effects depends on process parameters such as temperature, time, and the food matrix. Thermal processing can be detrimental to bioactive compounds while nonthermal procedures may not cause significant deterioration of important health-promoting phytochemicals and in some cases can improve their bio-activity and bio-availability. The detrimental effects of conventional processing on the quality of natural antioxidants have been compared to the effects of innovative nonthermal food treatments such as gamma and ultraviolet irradiation, ultraviolet light, pulsed electric fields, and high hydrostatic pressure.

High pressure processing effect on different Listeria spp. in a commercial starter-free fresh cheese

In this study, both microbial inactivation and growth of Listeria spp. inoculated in commercial free-starter fresh cheese was evaluated after high-pressure processing (HPP). HPP conditions (300, 400, 500 and 600 MPa at 6 °C for 5 min) and inoculum level (3-4 or 6-7 log CFU/g of cheese), as well as differences among strains inoculated (Listeria innocua, L. monocytogenes CECT 4031 and L. monocytogenes Scott A) were investigated. Inactivation and generation of sublethal injury were determined after HPP using ALOA (Agar Listeria according to Ottaviani and Agosti) and TAL (Thin Agar Layer) plating methods, respectively. Listeria inactivation increased with the pressure applied, presenting some statistical differences between the employed strains, inoculum level and sublethal injury. The highest lethality values were obtained at 600 MPa for the three strains tested, although the 500 MPa treatment presented high lethality for L. innocua and L. monocytogenes CECT 4031. After treatment, L. innocua and L. monocytogenes CECT 4031 counts in fresh cheese increased gradually during cold storage. By contrast, counts in cheeses inoculated with L. monocytogenes Scott A did not change significantly (p ≥ 0.05), being this strain the most pressure resistant and with the slowest growth rate. The manuscript present information supporting that, strains with high-level resistance should be employed during inactivation studies, instead of surrogate microorganisms. Application of HPP treatments of 500 MPa and especially 600 MPa on fresh cheeses would be effective to eliminate the most resistant microorganism to a level that should not present a public health risk under normal conditions of distribution and storage.

Relating Food Engineering to Cooking and Gastronomy

Modern consumers are increasingly eating meals away from home and are concerned about food quality, taste, and health aspects. Food engineering (FE) has traditionally been associated with the industrial processing of foods; however, most underlying phenomena related to FE also take place in the kitchen during meal preparation. Although chemists have positively interacted with acclaimed chefs and physicists have used foods as materials to demonstrate some of their theories, this has not been always the case with food engineers. This review addresses areas that may broaden the vision of FE by interfacing with cooking and gastronomy. Examples are presented where food materials science may shed light on otherwise empirical gastronomic formulations and cooking techniques. A review of contributions in modeling of food processing reveals that they can also be adapted to events going on in pots and ovens, and that results can be made available in simple terms to cooks. Industrial technologies, traditional and emerging, may be adapted to expand the collection of culinary transformations, while novel equipment, digital technologies, and laboratory instruments are equipping the 21st-century kitchens. FE should become a part of food innovation and entrepreneurship now being led by chefs. Finally, it is suggested that food engineers become integrated into gastronomy's concerns about safety, sustainability, nutrition, and a better food use.

Extraction of bioactive compounds and essential oils from mediterranean herbs by conventional and green innovative techniques: A review

Market interest in aromatic plants from the Mediterranean is continuously growing mainly due to their medicinal and bioactive compounds (BACs) with other valuable constituents from essential oils (EOs). From ancient times, these plants have been important condiments for traditional Mediterranean cuisine and remedies in folk medicine. Nowadays, they are considered as important factors for food quality and safety, due to prevention of various deteriorative factors like oxidations and microbial spoilage. EOs have different therapeutic benefits (e.g. antioxidant, anti-inflammatory, antimicrobial, and antifungal), while BACs mostly affect nutritive, chemical, microbiological, and sensory quality of foods. Currently, many plant extracts are used for functional (healthy) foods, which additionally fuels consumer and industrial interest in sustainable and non-toxic routes for their production. EO yields from dried plants are below 5%. Their extraction is strongly dependent on the hydrophobic or lipophilic character of target molecules, hence the common use of organic solvents. Similarly, BACs encompass a wide range of substances with varying structures as reflected by their different physical/chemical qualities. Thus, there is a need to identify optimal non-toxic extraction method(s) for isolation/separation of EO/BCs from plants. Various innovative non-thermal extractions (e.g. ultrasound-, high-pressure-, pulsed electric fields assisted extraction, etc.) have been proposed to overcome the above mentioned limitations. These techniques are "green" in concept, as they are shorter, avoid toxic chemicals, and are able to improve extract yields and quality with reduced consumption of energy and solvents. This research provides an overview of such extractions of both BAC and EOs from Mediterranean herbs, sustained by innovative and non-conventional energy sources.

The physical and biochemical effects of pre-rigor high pressure processing of beef

High pressure processing (HPP) of pre-rigor longissimus thoracis (strip loin) from prime and bull animals substantially decreased the shear force and improved consumer eating attributes of the final meat product. The improved tenderness in both prime and bull meat was associated with a lower myofibrillar fragmentation index and reduced calpain 1 activity which indicated the mechanism of tenderisation was different from that which occurred in chill aged meat. Light microscopy showed disruption to the fibre packing within the muscle and electron microscopy confirmed significant disruption of the Z discs and M lines and disappearance of the A lines. Thus, HPP is associated with a reduction in the structural integrity and strength of the sarcomeres. These effects were consistent in strip loins sourced from prime and bull stock. HPP also led to the movement of glycogen phosphorylase from the sarcoplasmic fraction to the insoluble myofibrillar fraction in all animals and this was associated with a higher pH at 24 h.