Effects of high pressure treatment (100–200 MPa) at low temperature on turbot (Scophthalmus maximus) muscle

Ice crystallization and structural changes in cheese during freezing and frozen storage: implications for functional properties

Temperature-mediated preservation techniques offer a simple, scalable, effective, and fairly efficient method of long-term storage of food products. In order to ensure the uninterrupted availability of cheese across the globe, a critical understanding of its techno-functional properties as affected by freezing and frozen storage is essential. Detailed studies of temperature-mediated molecular dynamics are available for relatively simpler and homogeneous systems like pure water, proteins, and carbohydrates. However, for heterogeneous systems like cheese, inter-component interactions at sub-zero temperatures have not been extensively covered. Ice crystallization during freezing causes dehydration of caseins and the formation of concentration gradients within the cheese matrix, causing undesirable changes in texture-functional attributes, but findings vary due to experimental conditions. A suitable combination of sample size, freezing rate, aging, and tempering can extend the shelf life of high- and low-moisture Mozzarella cheese. However, limited studies on other cheeses suggest that effects and suitability differ by cheese type, in most cases adversely affecting texture and functional attributes. This review presents an overview of the understanding of the effects of refrigeration, freezing techniques, and frozen storage on structural components of cheese, most prominently Mozzarella cheese, and the corresponding impact on microstructure and functionality. Also included are the mechanism of ice formation and relevant mathematical models for estimation of the thermophysical properties of cheese to assist in designing optimized schemes for their frozen storage. The review also highlights the lack of unanimity in critical understanding concerning the effect of freezing on the long-term storage of Mozzarella cheese with respect to its functionality.

Combining high pressure and electric fields towards Nannochloropsis oculata eicosapentaenoic acid-rich extracts

Nannochloropsis oculata is naturally rich in eicosapentaenoic acid (EPA). To turn this microalga into an economically viable source for commercial applications, extraction efficiency must be achieved. Pursuing this goal, emerging technologies such as high hydrostatic pressure (HHP) and moderate electric fields (MEF) were tested, aiming to increase EPA accessibility and subsequent extraction yields. The innovative approach used in this study combined these technologies and associated tailored, less hazardous different solvent mixtures (SM) with distinct polarity indexes. Although the classical Folch SM with chloroform: methanol (PI 4.4) provided the highest yield concerning total lipids (166.4 mg_lipid/g_biomass), diethyl ether: ethanol (PI 3.6) presented statistically higher values in terms of EPA per biomass, corresponding to 1.3-fold increase. When SM were used in HHP and MEF, neither technology independently improved EPA extraction yields, although the sequential combination of technologies did result in 62% increment in EPA extraction. Overall, the SM and extraction methodologies tested (HHP-200 MPa, 21 °C, 15 min, followed by MEF processing at 40 °C, 15 min) enabled increased EPA extraction yields from wet N. oculata biomass. These findings are of high relevance for the food and pharmaceutical industries, providing viable alternatives to the "classical" extraction methodologies and solvents, with increased yields and lower environmental impact. KEY POINTS: • Et₂O: EtOH is a less toxic and more efficient alternative to Folch solvent mixture • HHP or MEF per se was not able to significantly increase EPA extraction yield • Combinations of HHP and MEF technologies increased both lipids and EPA yields.

Using OPLS-DA to Fingerprint Key Free Amino and Fatty Acids in Understanding the Influence of High Pressure Processing in New Zealand Clams

This study investigated the effect of high pressure processing (HPP) on the fatty acids and amino acids content in New Zealand Diamond Shell (Spisula aequilatera), Storm Shell (Mactra murchisoni), and Tua Tua (Paphies donacina) clams. The clam samples were subjected to HPP with varying levels of pressure (100, 200, 300, 400, 500, and 600 MPa) and holding times (5 and 600 s) at 20 °C. Partial Least Squares Discriminant Analysis (PLS-DA) and Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA) were deployed to fingerprint the discriminating amino and fatty acids post-HPP processing while considering their inherent biological variation. Aspartic acid (ASP), isoleucine (ILE), leucine (LEU), lysine (LYS), methionine (MET), serine (SER), threonine (THR), and valine (VAL) were identified as discriminating amino acids, while C18:0, C22:1n9, C24:0, and C25:5n3 were identified as discriminating fatty acids. These amino and fatty acids were then subjected to mixed model ANOVA. Mixed model ANOVA was employed to investigate the influence of HPP pressure and holding times on amino acids and fatty acids in New Zealand clams. A significant effect of pressure levels was reported for all three clam species for both amino and fatty acids composition. Additionally, holding time was a significant factor that mainly influenced amino acid content. butnot fatty acids, suggesting that hydrostatic pressure hardly causes hydrolysis of triglycerides. This study demonstrates the applicability of OPLS-DA in identifying the key discriminating chemical components prior to traditional ANOVA analysis. Results from this research indicate that lower pressure and shorter holding time (100 MPa and 5 s) resulted in the least changes in amino and fatty acids content of clams.

Tenderization of Beef Semitendinosus Muscle by Pulsed Electric Field Treatment with a Direct Contact Chamber and Its Impact on Proteolysis and Physicochemical Properties

In this study, the effects of pulse electric field (PEF) treatment on the tenderization of beef semitendinosus muscle were investigated. An adjustable PEF chamber was designed to make direct contact with the surface of the beef sample without water as the PEF-transmitting medium. PEF treatment was conducted with electric field strengths between 0.5 and 2.0 kV/cm. The pulse width and pulse number were fixed as 30 μs and 100 pulses, respectively. The impedance spectrum of PEF-treated beef indicated that PEF treatments induced structural changes in beef muscle, and the degree of the structural changes was dependent on the strength of the electric field. Cutting force, hardness, and chewiness were significantly decreased at 2.0 kV/cm (35, 37, and 34%, respectively) (p < 0.05). Troponin-T was more degraded by PEF treatment at 2.0 kV/cm intensity (being degraded by 90%). The fresh quality factors such as color and lipid oxidation were retained under a certain level of PEF intensity (1.0 kV/cm). These findings suggest that PEF treatment could tenderize beef texture while retaining its fresh quality.

Effects of Ozone Water Combined With Ultra-High Pressure on Quality and Microorganism of Catfish Fillets (Lctalurus punctatus) During Refrigeration

This study described the quality and microbial influence on ozone water (OW) and ultra-high pressure (UHP) processing alone or in combination with refrigerated catfish fillets. The analysis parameters included total volatile base nitrogen (TVBN), thiobarbituric acid reactive substances (TBARs), chromaticity, microbial enumeration, 16S rRNA gene sequencing, electronic nose (E-nose), and sensory score. The study found that compared with the control (CK), ozone water combined with ultra-high pressure (OCU) delayed the accumulation of TVBN and TBARs. The results of sensory evaluation illustrated that OCU obtained a satisfactory overall sensory acceptability. The counting results suggested that compared to CK, OCU significantly (p < 0.05) delayed the stack of TVC, Enterobacteriaceae, Pseudomonas, lactic acid bacteria (LAB), and hydrogen sulfide-producing bacteria (HSPB) during the storage of catfish fillets. The sequencing results reflected that the dominant were Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria at the phylum level, and the dominant were Acinetobacter, Pseudomonas, Lelliottia, Serratia, Shewanella, Yersinia, and Aeromonas at the genus level. The dominant was Acinetobacter in initial storage, while Pseudomonas and Shewanella were in anaphase storage. Based on the TVC and TVBN, the shelf life of catfish fillets was extended by at least 3 days compared to the control. In short, the combination of ozone water and ultra-high-pressure processing is a favorable strategy to control microbial quality and delay lipid oxidation during catfish storage.

Effect of High-Pressure Processing on Physico-Chemical, Microbiological and Sensory Traits in Fresh Fish Fillets (Salmo salar and Pleuronectes platessa)

High-pressure (HP) treatment could lead to several advantages when applied to fish and seafood since it would affect the extension of the shelf life of this highly perishable food. In this regard, this study aimed to evaluate the effect of high-pressure treatment (500 MPa for 2 min at a temperature of 4 °C) on changes in quality on two different kinds of fresh fish fillets (Salmo salar and Pleuronectes platessa). Specifically, physico-chemical (VOCs, untargeted metabolomics spectra, pH and color), microbiological (Enterobacteriaceae, Pseudomonas spp., mesophilic and psychrotrophic bacteria) and sensory traits were evaluated at different days of refrigerated storage. From the results obtained, it is possible to state that the high pressure significantly (p ≤ 0.05) reduced microbial growth for each investigated microorganism. Regarding the colorimetric coordinates, no remarkable effects on a* and b* indices were found, while a significant effect (p = 0.01) was observed on the colorimetric index L*, making the HP-treated samples lighter than their respective controls. The sensory analysis showed that for the odor attribute, the HP treatment seems to have had a stabilizing action during shelf-life. Moreover, the treated samples obtained a better score than the respective controls (p ≤ 0.05). With regards to texture and appearance attributes, the treatment seems to have had a significant (p ≤ 0.05) effect, making the treated samples more compact and opaque than controls, therefore resulting in the loss of the characteristics of raw fish for the treated samples. Moreover, from a chemical point of view, HP treatment prevents the development of volatile sulfides and delays the formation of histamine (p ≤ 0.05). Very interestingly, the metabolomic approach revealed novel dipeptide markers for the HP procedure.

Application of high hydrostatic pressure on Pacific white shrimp (Litopenaeus vannamei) pâté: Microbiological, physicochemical and consumer acceptance

The locally elaborated shrimp pâté is highly susceptible to microbial spoilage and deterioration during storage due to its content in nutrients. These conditions limit its commercialization in a larger scale. High hydrostatic pressure is an alternative to heat treatments technology used to inactivate microorganisms. The aim of this project was to evaluate the effect of high hydrostatic pressure on quality parameters and microbiological stability of Pacific white shrimp ( Litopenaeus vannamei) pâté during storage. Shrimp pâté was pressurized to 400, 500 and 600 MPa for 90 and 180 s. Samples were analysed for physicochemical, microbiological and flavour profile up to 21 days of storage at 4 ℃. A hedonic test was made to evaluate the acceptance of pâté. No microorganisms were detected at 600 MPa for 180 s and a shelf life of 14 days was reached. No relevant changes in pH or colour of pressurized samples were detected; flavour profile did not show any changes after being pressurized or during storage. Shrimp pâté treated with 600 MPa for 180 s presented good sensory acceptance. High hydrostatic pressure treatments could improve microbiological quality of shrimp pâté without a sensible modification of the physicochemical and sensorial qualities of this product.

Effects of Ultra High Pressure on Bay Scallop (Aequipecten irradians) Adductor Muscles

The aim of this study was to evaluate the effects of ultra high pressure (UHP) on the adductor muscles of bay scallops ( Aequipecten irradians) pertaining to certain physicochemical characteristics and microstructure. UHP treatment was applied at 200MPa and 400MPa, each application with one pulse and a holding time of 10min, or 2 pulses and a holding time of 5min per pulse, in a continuous or oscillation mode. Determination of textural parameters and L*, a* and b* colour parameters were carried out and compared with untreated scallops. Microstructure was observed using a scanning electronic microscopy (SEM) technique and, for microbial analyses, a total plate count was performed. SEM showed that UHP treatments induced a size reduction of the honeycomb structure of myofibres, giving a more compact appearance to the structure. Colour and compressibility enhanced by pressure treatment, however loss of hardness was observed. UHP treatments also reduced the initial load in total plate count of microorganisms to 10cfu/g. UHP is a competitive technology in food processing and ready for use on this high-priced seafood product.

Effects of high hydrostatic pressure and temperature increase on Escherichia coli spp. and pectin methyl esterase inactivation in orange juice

The aim of this study was to evaluate the effect of high hydrostatic pressure treatment combined with moderate processing temperatures (25 ℃-50 ℃) on the inactivation of Escherichia coli O157: H7 (ATCC 700728), E. coli K12 (ATCC 23716), and pectin methyl esterase in orange juice, using pressures of 250 to 500 MPa with times ranging between 1 and 30 min. Loss of viability of E. coli O157:H7 increased significantly as pressure and treatment time increased, achieving a 6.5 log cycle reduction at 400 MPa for 3 min at 25 ℃ of treatment. With regard to the inactivation of pectin methyl esterase, the greatest reduction obtained was 90.05 ± 0.01% at 50 ℃ and 500 MPa of pressure for 15 min; therefore, the pectin methyl esterase enzyme was highly resistant to the treatments by high hydrostatic pressure. The results obtained in this study showed a synergistic effect between the high pressure and moderate temperatures in inactivating E. coli cells.

High Pressure Treatment in Foods

High hydrostatic pressure (HHP), a non-thermal technology, which typically uses water as a pressure transfer medium, is characterized by a minimal impact on food characteristics (sensory, nutritional, and functional). Today, this technology, present in many food companies, can effectively inactivate bacterial cells and many enzymes. All this makes HHP very attractive, with very good acceptance by consumers, who value the organoleptic characteristics of products processed by this non-thermal food preservation technology because they associate these products with fresh-like. On the other hand, this technology reduces the need for non-natural synthetic additives of low consumer acceptance.