A Study of Electrode Material Performance During Food Processing by Pulsed Electric Fields

Upon the application of high-field pulses across a liquid food product (such as milk, juices, or beer), electric charge accumulates across the membrane of any microbial cell present in the processing zone between the two electrodes. Within a few hundred nanoseconds, this charge accumulation results in an irreversible membrane breakdown which causes the cell to lose its viability. By this means, an extended shelf-life could be achieved. Thus, the use of pulsed electric fields (PEFs) provides an alternative method to preserve liquid food products instead of the conventional thermal pasteurization. The advantages of using the PEF processing over conventional thermal pasteurization include greater retention of the original nutritional value and fresh-like taste, less usage of processing energy, and lower contamination from the processing equipment. Physical and electrical contact between the liquid food product and the metallic electrodes during the PEF processing is unavoidable and causes some metallic ions to be released from the electrodes into the processed food. This undesirable release of metallic ions from the electrodes can affect food safety and taste, degrade food compounds/color, and shorten the electrode lifetime over a long period of use. As such, it represents one of the main challenges for the commercialization of such non-thermal preservation technique. In this study, the concentration of released metallic ions in PEF-processed milk, orange juice, and beer has been determined using the inductively coupled plasma – atomic emission spectroscopy (ICP-AES) under various operating conditions. It has been found that the mitigation of arcing events protects the electrode surface from experiencing “pits”, which is one source of metallic ion release. For electrochemical reactions, satisfying a “zero net charge delivery” reduces the metallic content of PEF-processed foods considerably. Allowing the charging current of the generator’s capacitor to flow through the PEF processing chamber is used here to ensure the zero net charge delivery with mono-polar pulses. Lower metallic content has been obtained by using pulses of shorter width; this observation agrees with the nature of an electrically-driven electrochemical process. Variation in the voltage peak, within the typical PEF conditions, did not have a significant effect on metal release. The comparison of the behavior of electrodes coated with chromium, nickel, silver, and titanium has revealed the superior performance of titanium. A solid titanium electrode did not lead to any detectible metal release after PEF processing of milk (neutral) and orange juice (acidic); whereas, the concentration of iron from stainless steel electrodes was detectible in both liquids. The temperature of the PEF processing zone did not influence the metallic content when varied in the range from 1° to 30ºC. The study also highlights the applicability of the PEF processing on carbonated beer, in particular through a sealed and pressurized processing chamber. Brewery regulations in Canada do not necessitate the thermal pasteurization of carbonated beer; hence, PEF processing finds a potential application in the beer industry. Sensory panels have shown that PEF-processed beer is preferred when compared to thermally pasteurized beer with respect to flavor, aroma, and foam condition. Untrained panelists preferred samples processed with low-dosage of PEF in week 0, but preferred samples with high-dosage in week 12 of the shelf-life. Trained panelists reported a metallic feeling in the PEF-processed beer which could be due to the presence of metallic ions that was detected analytically

Resistant moulds as pasteurization target for cold distributed high pressure and heat assisted high pressure processed fruit products

Part of this study was presented by Filipa V.M. Silva at XII Congresso IberoAmericano de Engenharia de Alimentos (CIBIA, IberoAmerican Congress of Food Engineering), Challenging Food Engineering as a Driver Towards Sustainable Food Processing, 1–4 July 2019, Faro, PortugalHigh pressure processing (HPP), also known as high hydrostatic pressure (HHP) is a modern method of food pasteurization used commercially in many countries. It relies on the application of very high pressures (up to 600 MPa) to the food/beverage to inactivate microorganisms. Since no heat or mild heat is applied, most of the original food sensory, nutrient and functional properties are retained after processing, and fresh-like fruit products with longer shelf-life are produced. In this study, a review of the resistance to HPP and HPTP (high pressure thermal process) of key bacteria, moulds and yeasts which often contaminate fruit products was un dertaken. Spores of moulds Byssochlamys nivea - anamorph name Paecilomyces niveus or Neosartorya fischeri - anamorph name Aspergillus fischeri, are very resistant. A HPTP process of 600 MPa-75ºC-15 min only caused a reduction of 1.4 log. Moulds are able to grow at temperatures between 10 and 43 ºC, water activity between 0.892 and 0.992, over a wide range of pH (3–8), under reduced oxygen conditions inside food packs and in carbonated beverages, sometimes producing mycotoxins. Furthermore, HPP treated fruit products are cold stored, and therefore moulds can be an issue as they grow at temperatures as low as 10 ºC. Therefore, in view of the acidity of fruit products, the high resistance to HPTP in particular older spores, the use of B. nivea or N. fischeri spores as reference microorganisms in the design of new HPP and HPTP processes with fruit products was proposedinfo:eu-repo/semantics/publishedVersio

Two decades of "Horse sweat" taint and Brettanomyces yeasts in wine: where do we stand now ?

ReviewThe unwanted modification of wine sensory attributes by yeasts of the species Brettanomyces bruxellensis due to the production of volatile phenols is presently the main microbiological threat to red wine quality. The effects of ethylphenols and other metabolites on wine flavor is now recognized worldwide and the object of lively debate. The focus of this review is to provide an update of the present knowledge and practice on the prevention of this problem in the wine industry. Brettanomyces bruxellensis, or its teleomorph, Dekkera bruxellensis, are rarely found in the natural environment and, although frequently isolated from fermenting substrates, their numbers are relatively low when compared with other fermenting species. Despite this rarity, they have long been studied for their unusual metabolical features (e.g., the Custers effect). Rising interest over the last decades is mostly due to volatile phenol production affecting high quality red wines worldwide. The challenges have been dealt with together by researchers and winemakers in an effective way and this has enabled a state where, presently, knowledge and prevention of the problem at the winery level is readily accessible. Today, the main issues have shifted from technological to sensory science concerning the effects of metabolites other than ethylphenols and the over estimation of the detrimental impact by ethylphenols on flavor. Hopefully, these questions will continue to be tackled together by science and industry for the benefit of wine enjoymentinfo:eu-repo/semantics/publishedVersio

Fruit-based fermented beverages : contamination sources and emerging technologies applied to assure their safety

The food and beverage market has become broader due to globalization and consumer claims. Under the umbrella of consumer demands, legislation, nutritional status, and sustainability, the importance of food and beverage safety must be decisive. A significant sector of food production is related to ensuring fruit and vegetable conservation and utilization through fermentation. In this respect, in this review, we critically analyzed the scientific literature regarding the presence of chemical, microbiological and physical hazards in fruit-based fermented beverages. Furthermore, the potential formation of toxic compounds during processing is also discussed. In managing the risks, biological, physical, and chemical techniques can reduce or eliminate any contaminant from fruitbased fermented beverages. Some of these techniques belong to the technological flow of obtaining the beverages (i.e., mycotoxins bound by microorganisms used in fermentation) or are explicitly applied for a specific risk reduction (i.e., mycotoxin oxidation by ozone). Providing manufacturers with information on potential hazards that could jeopardize the safety of fermented fruit-based drinks and strategies to lower or eliminate these hazards is of paramount importance.info:eu-repo/semantics/publishedVersio

APPLICATIONS OF ULTRASOUND IN FOOD PROCESSING

Nowadays, researchers are interested in minimal food processing techniques because of the increasing fresh or fresh-like food preferences of the consumers. Ultrasound is an acoustic energy but, its effect is a result of physical energy which is generated by the kinetic energy of the molecules in the applied medium. Its powerful effect, drawn the interest of the scientists to investigate on its applications in many areas. In food science, ultrasound has a wide range of applications. Microbial inactivation, drying, filtration, extraction, homogenization, cutting, emulsifying, cleaning, degassing and inactivation of enzymes are some of the examples of efficient ultrasound applications. The two important well-known benefits of using ultrasound are the reduction of the process duration and process cost. In this review, some ultrasound applications will be discussed in food science and technology

Saccharomycodes ludwigii, control and potential uses in winemaking processes

Non-Saccharomyces yeasts are becoming important because most of them are considered as spoilage species in winemaking processes, among them the species Saccharomycodes ludwigii. This species is frequently isolated at the end of the fermentation process and/or during storage of the wine, i.e., it can to grow in the presence of high levels of ethanol. Besides, this species is adaptable to unfavorable conditions such as high concentrations of SO2 and is characterized by its capacity to produce high amounts of undesirable metabolites as acetoin, ethyl acetate or acetic acid. To the present, physical (gamma irradiation and continuous pulsed electric fields), chemical (inhibitory compounds such as chitosan and dimethyl dicarbonate) and biological (antagonistic biocontrol by killer yeasts) treatments have been developed in order to control the growth of this spoilage yeast in wines and other fruit derivatives. Therefore, this review is focused on the most relevant studies conducted to control contamination by S. ludwigii. Moreover, potential applications of S. ludwigii in alternative winemaking techniques, for example for ageing-on-lees and stabilization of red wines, and improvement of aromatic profile are also examined

Modeling of yeast thermal resistance and optimization of the pasteurization treatment applied to soft drinks

open8noYeast are usually responsible for spoilage of soft drinks and fruit beverages, because of the particular characteristics of these products (low pH, high C/N ratio). The microbial stability is guaranteed by thermal treatments. However, excessive heat treatments can affect food sensorial quality. In this work the thermal resistance of different yeasts strains (seven belonging to the species Saccharomyces cerevisiae and six belonging to the species Kluyveromyces marxianus, Zygosaccharomyces bisporus, Z. mellis, Z. rouxii, Schizosaccharomyces pombe and Saccharomycodes ludwigii) was assessed in a model system. The results showed non-linear death curves and a high variability also within the same species. The most resistant strain, belonging to the species S. cerevisiae, was chosen for further experiments in orange juice based industrial beverages: first, death curves were performed; then, the probability of beverage spoilage in relation to process parameters (initial inoculum, temperature, treatment time) was evaluated using a logistic regression model. Finally, a cross-validation was performed to investigate the predictive capability of the fitted model. Pasteurization in the soft drink industry is commonly applied according to parameters defined several decades ago, which does not consider the successive findings concerning microbial physiology and stress response, the process improvement and the more recent tools provided by predictive microbiology. In this perspective, this study can fill a gap in the literature on this subject, going to be a basis for optimizing thermal processes. In fact, the data obtained indicated an interesting possibility for food industry to better modulated (and even reduce) thermal treatments, with the aim to guarantee microbial stability while reducing thermal damage and energy costs.embargoed_20200731Montanari, Chiara; Tabanelli, Giulia; Zamagna, Ilaria; Barbieri, Federica; Gardini, Aldo; Ponzetto, Mauro; Redaelli, Erika; Gardini, FaustoMontanari, Chiara; Tabanelli, Giulia; Zamagna, Ilaria; Barbieri, Federica; Gardini, Aldo; Ponzetto, Mauro; Redaelli, Erika; Gardini, Faust

An overview of the factors influencing apple cider sensory and microbial quality from raw materials to emerging processing technologies

Given apple, an easily adapted culture, and a large number of apple varieties, the production of apple cider is widespread globally. Through the fermentation process, a series of chemical changes take place depending on the apple juice composition, type of microorganism involved and technology applied. Following both fermentations, alcoholic and malo-lactic, and during maturation, the sensory profile of cider changes. This review summarises the current knowledge about the influence of apple variety and microorganisms involved in cider fermentation on the sensory and volatile profiles of cider. Implications of both Saccharomyces, non-Saccharomyces yeast and lactic acid bacteria, respectively, are discussed. Also are presented the emerging technologies applied to cider processing (pulsed electric field, microwave extraction, enzymatic, ultraviolet and ultrasound treatments, high-pressure and pulsed light processing) and the latest trends for a balanced production in terms of sustainability, authenticity and consumer preferences

Relevant Fusarium mycotoxins in malt and beer

Mycotoxins are secondary fungal metabolites of high concern in the food and feed industry. Their presence in many cereal-based products has been numerously reported. Beer is the most consumed alcoholic beverage worldwide, and Fusarium mycotoxins originating from the malted and unmalted cereals might reach the final product. This review aims to describe the possible Fusarium fungi that could infect the cereals used in beer production, the transfer of mycotoxins throughout malting and brewing as well as an insight into the incidence of mycotoxins in the craft beer segment of the industry. Studies show that germination is the malting step that can lead to a significant increase in the level of all Fusarium mycotoxins. The first step of mashing (45 oC) has been proven to possess the most significant impact in the transfer of hydrophilic toxins from the grist into the wort. However, during fermentation, a slight reduction of deoxynivalenol, and especially of zearalenone, is achieved. This review also highlights the limited research available on craft beer and the occurrence of mycotoxins in these products.The authors are thankful to the MCIN/ AEI /10.13039/501100011033 for financ‐ ing the present work (Project PID2020‐114836RB‐I00). Xenia Pascari also thanks the Ministry of Sci‐ ence and Innovation for her postdoctoral scholarship