There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

In recent years, there has been a growing interest in the design of novel nonthermal processing systems that minimally modify sensory, nutritional, and functional properties of fruit and vegetable juices and beverages. The benefits of nonthermal treatments are strongly dependent on the food matrix. Thus, an understanding of the effects that these technologies exert on the properties of juices and beverages is important to design and optimize technological parameters to produce value-added products. This review covers research on nonthermal electrical treatments, high pressure processing, ultrasound, radiation processing, inert gas treatments, cold plasma, and membrane processing. Advances towards optimization of processing conditions, and combined technologies approaches have been also extensively reviewed. This information could be useful to: (1) manage processing systems and optimize resources; (2) preserve nutritional value and organoleptic properties, and (3) provide processing conditions for validation of these technologies at the industrial scale.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/1541-4337.12299

Nonthermal Technologies for Fruit and Vegetable Juices and Beverages: Overview and Advances.

This paper provides an overview of alternatives to conventional thermal treatments and a review of the literature on fruit-juice processing for three key operations in fruit-juice production such as microbial inactivation, enzyme inactivation, and juice yield enhancement, these being radiation treatments (UV light, high-intensity light pulses, γ-irradiation), electrical treatments (pulsed electric fields, radiofrequency electric fields, ohmic heating), microwave heating, ultrasound, high hydrostatic pressure, inert gas treatments (supercritical carbon dioxide, ozonation), and flash-vacuum expansion. The nonthermal technologies discussed in this review have the potential to meet industry and consumer expectations. However, the lack of standardization in operating conditions hampers comparisons among different studies, and consequently ambiguity arises within the literature. For the juice industry to advance, more detailed studies are needed on the scaling-up, process design, and optimization, as well as on the effect of such technologies on juice quality of juices in order to maximize their potential as alternative nonthermal technologies in fruit-juice processing.

Alternatives to conventional thermal treatments in fruit-juice processing. Part 1: Techniques and applications.

Enzymatic browning is associated to the colour alteration and phenolic degradation of minimally-processed fruits and vegetables. The main responsible is polyphenol oxidase (PPO, EC 1.14.18.1), a copper-containing oxidoreductase which catalyzes two different enzymatic reactions involving oxygen and polyphenolic substrates which are polymerized to dark pigments. Since the control of PPO activity is until now an open question in the agro-food industry, the search for new anti-browning strategies is moving towards replacing conventional treatments. The present review is aimed to discuss non-thermal technologies and natural inhibitors considering their anti-PPO impact in relation to enzyme source, processing conditions, type and concentration of bioactive compounds. These innovative treatments can be proposed as eco-friendly systems for effectively reducing PPO activity thus preventing enzymatic browning and consequently improving sensory, antioxidant and nutritional properties of fruit and vegetable products.

Recent advances in controlling polyphenol oxidase activity of fruit and vegetable products

Bacteriophages are viruses that are ubiquitous in nature and infect only bacterial cells. These organisms are characterized by high specificity, an important feature that enables their use in the food industry. Phages are applied in three sectors in the food industry: primary production, biosanitization, and biopreservation. In biosanitization, phages or the enzymes that they produce are mainly used to prevent the formation of biofilms on the surface of equipment used in the production facilities. In the case of biopreservation, phages are used to extend the shelf life of products by combating pathogenic bacteria that spoil the food. Although phages are beneficial in controlling the food quality, they also have negative effects. For instance, the natural ability of phages that are specific to lactic acid bacteria to destroy the starter cultures in dairy production incurs huge financial losses to the dairy industry. In this paper, we discuss how bacteriophages can be either an effective weapon in the fight against bacteria or a bane negatively affecting the quality of food products depending on the type of industry they are used.

Bacteriophages-a new hope or a huge problem in the food industry.

Supercritical carbon dioxide (SCCD) was applied for strawberry juice preservation. SCCD under selected parameters was effective for microflora and enzyme inactivation. For storage studies samples preserved at 30 and 60 MPa, at 45 °C for 30 min were selected. Yeasts and moulds were not detected after SCCD treatment in these conditions, whereas TMC was ~ 1.7 log CFU/g. Polyphenol oxidases were inactivated, whereas peroxidases decreased by ~ 85%. SCCD treatment resulted in the hydrolysis of sucrose and ~ 30% losses of vitamin C, which was totally decomposed after the 4th week of storage. Anthocyanins were not affected by the SCCD process and the kinetic rate constant of degradation during storage ranged from 2.12 × 10 − 2 to 3.10 × 10 − 2 (days − 1 ), and the half-time from 22.4 to 32.7 days, depending on the monomer and pressure applied. Overall, SCCD treatment seems to be a promising technique to obtain high quality strawberry juice as a safe alternative to non-pasteurized juices. Industrial relevance Strawberries are highly appreciated for their nutritional quality, colour and taste. Strawberry compounds, i.e. anthocyanins and vitamin C, are heat sensitive. These nutrients as well as colour are degraded when the fruits are processed using high temperature treatment. Supercritical carbon dioxide (SCCD) is an interesting method among the innovative non-thermal technologies for the preservation of fruit products. In this study, the data proved that SCCD processing is a promising non-thermal alternative to pasteurization to preserve fresh cloudy strawberry juice.

Application of supercritical carbon dioxide for the preservation of strawberry juice: Microbial and physicochemical quality, enzymatic activity and the degradation kinetics of anthocyanins during storage

Alicyclobacillus acidoterrestris, a thermoacidophilic and spore-forming bacterium is one of the important target micro-organisms in the quality control of acidic canned foods. High pressure pasteurization (HPP) at 50°C was used for the inactivation of A. acidoterrestris spores in apple juice. Pressure applied both in a continuous and oscillatory mode gave the best results when 200 MPa was used. Increasing the pressure to 500 MPa, as well as lowering its value to 100 MPa, had an adverse effect on the effectiveness of the process. The best results were achieved with the use of a combined treatment, involving oscillatory pressurization at 200 MPa, followed by holding the sample for 60 min at atmospheric pressure and subsequent pressurization at 500 MPa, resulting in a reduction in the spore count of 6.15 log. Nisin significantly enhanced the effect of HPP at 300 MPa. Using pressure of 200 MPa for 45 min with a nisin concentration of 250 IU/mL enabled total spore inactivation (over 6 log). No significant effe...

The combined effect of high pressure and nisin or lysozyme on the inactivation of Alicyclobacillus acidoterrestris spores in apple juice

Treatment with high hydrostatic pressure and supercritical carbon dioxide to control Alicyclobacillus acidoterrestris spores in apple juice

Alicyclobacillus acidoterrestris, a thermoacidophilic and spore-forming bacterium, survives the typical pasteurization process and can cause the spoilage of juices, producing compounds associated with disinfectant-like odour (guaiacol, 2,6 – dibromophenol, 2,6 – dichlorophenol). Therefore, the use of other more effective techniques such as high hydrostatic pressure (HHP) is considered for preserving juices. The aim of this study was to search for factors affecting the resistance of A. acidoterrestris spores to HHP. The baroprotective effect of increased solute concentration in apple juice on A. acidoterrestris spores during high pressure processing was observed. During the 45 min pressurization (200 MPa, 50°C) of the spores in concentrated apple juice (71.1°Bx), no significant changes were observed in their number. However, in the juices with a soluble solids content of 35.7, 23.6 and 11.2°Bx, the reduction in spores was 1.3–2.4 log, 2.6–3.3 log and 2.8–4.0 log, respectively. No clear effect of age of spo...

Barbara Sokołowska

Papers

Bacteriophages-a new hope or a huge problem in the food industry.

Application of supercritical carbon dioxide for the preservation of strawberry juice: Microbial and physicochemical quality, enzymatic activity and the degradation kinetics of anthocyanins during storage

The combined effect of high pressure and nisin or lysozyme on the inactivation of Alicyclobacillus acidoterrestris spores in apple juice

Treatment with high hydrostatic pressure and supercritical carbon dioxide to control Alicyclobacillus acidoterrestris spores in apple juice

Factors influencing the inactivation of Alicyclobacillus acidoterrestris spores exposed to high hydrostatic pressure in apple juice