High Pressure Processing Applications in Plant Foods

High pressure processing (HPP) is a cold pasteurization technology by which products, prepacked in their final package, are introduced to a vessel and subjected to a high level of isostatic pressure (300–600 MPa). High-pressure treatment of fruit, vegetable and fresh herb homogenate products offers us nearly fresh products in regard to sensorial and nutritional quality of original raw materials, representing relatively stable and safe source of nutrients, vitamins, minerals and health effective components. Such components can play an important role as a preventive tool against the start of illnesses, namely in the elderly. An overview of several food HPP products, namely of fruit and vegetable origin, marketed successfully around the world is presented. Effects of HPP and HPP plus heat on key spoilage and pathogenic microorganisms, including the resistant spore form and fruit/vegetable endogenous enzymes are reviewed, including the effect on the product quality. Part of the paper is devoted to the industrial equipment available for factories manufacturing HPP treated productsinfo:eu-repo/semantics/publishedVersio

Critical Review of Norovirus Surrogates in Food Safety Research: Rationale for Considering Volunteer Studies

The inability to propagate human norovirus (NoV) or to clearly differentiate infectious from noninfectious virus particles has led to the use of surrogate viruses, like feline calicivirus (FCV) and murine norovirus-1 (MNV), which are propagatable in cell culture. The use of surrogates is predicated on the assumption that they generally mimic the viruses they represent; however, studies are proving this concept invalid. In direct comparisons between FCV and MNV, their susceptibility to temperatures, environmental and food processing conditions, and disinfectants are dramatically different. Differences have also been noted between the inactivation of NoV and its surrogates, thus questioning the validity of surrogates. Considerable research funding is provided globally each year to conduct surrogate studies on NoVs; however, there is little demonstrated benefit derived from these studies in regard to the development of virus inactivation techniques or food processing strategies. Human challenge studies are needed to determine which processing techniques are effective in reducing NoVs in foods. A major obstacle to clinical trials on NoVs is the perception that such trials are too costly and risky, but in reality, there is far more cost and risk in allowing millions of unsuspecting consumers to contract NoV illness each year, when practical interventions are only a few volunteer studies away. A number of clinical trials have been conducted, providing important insights into NoV inactivation. A shift in research priorities from surrogate research to volunteer studies is essential if we are to identify realistic, practical, and scientifically valid processing approaches to improve food safety

Modification of the structural and rheological properties of whey protein/gelatin mixtures through high pressure processing

High pressure processing (HPP) can induce structure development in macromolecules which are distinct from those of conventional thermal treatments. Gelation properties of whey protein (5-20% w/w) upon 15 min HPP at 600 MPa and 5 or 30 °C (initial sample temperatures) were examined in the presence and absence of 5% w/w gelatin. The values of storage modulus (G')in pressure treated mixed gels were below those of their counterparts thermally treated at 80 °C. Mixed systems subjected to HPP in the solution state possessed higher G' than the mixed systems subjected to HPP in the form of gels. The cooling profile of G' in pressurised mixed solutions was similar to that of the gelatin solution, which indicates that HPP resulted in a high degree of gelatin continuity. Confocal images confirmed that gelatin was the continuous phase whilst whey protein aggregated in discontinuous inclusions within the pressurised mixed systems

Modeling counterion partition in composite gels of BSA with gelatin following thermal treatment

This study deals with the distribution of added calcium ions and their effect on the phase behaviour of hydrogels made of bovine serum albumin and gelatin. Structural properties of single and mixed systems were identified using small-deformation dynamic oscillation in shear, microdifferential scanning calorimetry and scanning electron microscopy. The experimental procedure was designed to encourage formation of micro phase-separated materials, where i) a continuous gelatin matrix supported liquid BSA inclusions, ii) an inverted dispersion of gelled BSA was interspersed by liquid gelatin inclusions and iii) a rigid BSA phase supported softer filler particles of gelatin. The Lewis-Nielsen equations and a series of models developed by Takayanagi were adapted for predicting the phase behaviour of BSA/gelatin mixtures in the presence of added calcium chloride. As far as we are aware, this is the first attempt to model the partition of added counterions between polymeric phases in binary hydrogels based on classic blending law analysis

Growth of superconducting epitaxial LaNixBi2pnictide thin films with a Bi square net layer by reactive molecular beam epitaxy

We have grown superconducting epitaxial thin films of LaNixBi2 which crystallize in the ZrCuSiAs structure with a peculiar Bi square net layer. This material represents an additional class of pnictide superconductors since superconductivity is assumed to occur in the Bi square net layer. Optimized thin films grown by molecular beam epitaxy have a superconducting transition temperature of around 4 K and are stable in ambient air

Structuring dairy systems through high pressure processing

This review highlights the current knowledge on gelation of hydrocolloids induced by high pressure processing (HPP) of dairy products. Pressure-induced gelation of single systems (casein rich, whey protein rich, gelatin, and polysaccharide solutions) as well as rheological and thermo-mechanical effects of HPP on mixture systems are discussed. The mechanism of dairy protein gelation under pressure, their properties and microstructure, and potential application of HPP to improve physical properties of dairy products (cheese, yoghurt, and ice cream) are included. HPP is a promising tool for future manufacturing of structured dairy products with unique sensorial properties