Ultrasound assisted thermal inactivation of spores in foods: Pathogenic and spoilage bacteria, molds and yeasts

Background: Pasteurization aims to achieve the reduction of vegetative microorganisms and resistant spores which are of risk to public health. Power ultrasound has been identified as a potential technology for non-thermal food pasteurization. It relies on the propagation of pressure waves (frequency ranging from 20 to 100 kHz) of high intensity sound/acoustic energy (10–1000 W/cm2) inside a liquid or semisolid food, causing inactivation of pathogenic and spoilage microorganisms. This technology can also be used in simultaneous combination with temperature >80 ◦C (thermosonication, TS) to inactivate microbial spores. Scope and approach: The current knowledge on the effect of ultrasound alone (US), TS, and ultrasound followed by a thermal process (US→T) on different type of spores relevant for low- and high-acidic foods was reviewed, including the kinetic models describing their inactivation in specific foods. Key findings and conclusions: US at room temperature (without heat) has no effect on microbial spores. In terms of microbial spore inactivation efficiency, TS was the best method, followed by US→T (non-simultaneous application) and finally heat treatment without US (T). TS employing temperatures between 90 ◦C and <100 ◦C is required for spore inactivation, as at the boiling point of water ultrasound intensity is reduced. There is a need to design efficient ultrasound probes which can withstand higher temperatures or incorporate pressure to improve gas bubble implosion, thus more results can be produced at higher temperatures and with different type of microorganisms. When reporting results from TS experiments, standardized ultrasound processing conditions including the actual power delivered to the food and expressed in acoustic power density (power/volume of liquid food, W/mL) or specific acoustic power (W/g food) should be used to allow the comparison of results from different studies. TS inactivation kinetics of some spores of bacteria and molds exhibited non-linear trends, thus TS should be examined in detail for reliable food processinginfo:eu-repo/semantics/publishedVersio

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

Optimisation of ultrasound assisted extraction of antiacetylcholinesterase and antioxidant compounds from manuka (Leptospermum scoparium) for use as a phytomedicine against Alzheimer's disease

Research ArticleBackground: Alzheimer’s disease is a progressive mental deterioration related to ageing and senility. Approved drugs that inhibit acetylcholinesterase (AChE) enzyme activity in the human brain are one of the ways to control the natural progression of this disease. The present study reports on the optimisation of ultrasound-assisted extraction of antiacetylcholinesterase and antioxidant compounds from manuka leaves using response surface methodology. Methods: A Box-Behnken design was used to investigate the effect of extraction temperature (40–60°C), time (1–20 min), and ethanol concentration (30–70%) on AChE inhibition, antioxidant activity, and extraction yield. Results: The values of AChE, radical scavenging activity (RSA) and yield predicted by the models generated were similar to the experimental values. Extraction time, ethanol concentration and temperature were significant in all the responses. Optimum extraction conditions for maximum AChE inhibition (74%), RSA (79%) and yield (50%) were successfully validated experimentally and the IC50 of the optimised extracts were reduced to 28.5 (from 66.0) and 2.37 (from 32.4) μg/ mL for AChE and antioxidant activity, respectively. The optimisation enabled an increase in the extraction yield from 21% to 49%. Conclusions: In view of the significant bioactive properties determined, with possible beneficial effects on memory deficit, we would encourage the use of the manuka leaf extract for the development of new phytopharmaceuticals to improve brain function and control dementias such as Alzheimer’s disease. One other application could be as a beverage for the preparation of tea infusionsinfo:eu-repo/semantics/publishedVersio

Alicyclobacillus acidoterrestris spores in fruit products and design of pasteurization processes

Alicyclobacillus acidoterrestris is a thermoacidophilic, nonpathogenic and sporeforming bacterium which has been found in commercial pasteurized fruit juices in the past. Only few and recent studies were available in the literature, since only in 1984 Cerny et al. [Cerny, G., Hennlich, W., & Poralla, K. (1984). Fruchtsaftverderb durch bacillen: isolierung und charakterisierung des verderbserregers. Z. Lebensmitt. Unters. Forsch. 179, 224-227] reported a spoiled aseptically packaged apple juice with A. acidoterrestris and in 1987 Deinhard et al. [Deinhard, G., Blanz, P., Poralla, K., & Altan, E. (1987). Bacillus acidoterrestris sp. nov., a new thermotolerant acidophile isolated from different soils. Systematic and Applied Microbiology, 10, 47-53] named first this species. Detection and identification methods for A. acidoterrestris were reviewed and data regarding heat resistance of spores and growth in fruits were collected. Finally, a new methodology to design pasteurization processes for high acidic fruit products is presented.FCT e União Europeiainfo:eu-repo/semantics/publishedVersio

The Effect of Processing Methods on Food Quality and Human Health: Latest Advances and Prospects

Editorial - Special IssueThis Special Issue is focused on the use of modern food processing technologies to retain the highest possible content of health-promoting compounds in raw foods. Additionally, these technologies enable the amount of salt and preservatives added to foods to be reduced. These additives are known to be prejudicial to human health, and are associated with a variety of health problemsinfo:eu-repo/semantics/publishedVersio

Control of Enzymatic Browning in Strawberry, Apple, and Pear by Physical Food Preservation Methods: Comparing Ultrasound and High-Pressure Inactivation of Polyphenoloxidase

Polyphenoloxidase (PPO) enzyme can be found in fruits, vegetables and crustaceans. Its activity, promoted by oxygen, causes food browning with subsequent loss of quality and limited shelf life. Foods are pasteurized with conventional and novel physical methods to inactivate spoilage enzymes, thus avoiding the addition of unhealthy chemical preservatives. Ultrasound and highpressure processing (HPP) are non-thermal technologies capable of retaining vitamins, bioactives and sensory components of fresh fruits. Enzyme residual activity vs. processing time were plotted for strawberry, apple, and pear purees subjected to thermosonication (1.3 W/g—71 C), HPP-thermal (600 MPa—71 C) and heat treatment alone at 71 C. The PPO residual activities after treatments were highly variable. TS was the most effective for inactivating PPO, followed by thermal processing. HPP-thermal did not improve the inactivation compared with thermal treatment at 71 C. The resistance of the three fruits’ PPOs exhibited the same pattern for the three technologies: pear PPO was the most resistant enzyme, followed by apple PPO and, lastly, strawberry PPO. However, the resistance of the three PPOs to TS was lower and very similar. Given the huge variability of PPO resistance, it is important to run inactivation tests for different fruits/cultivars. The results can assist manufacturers to avoid browning during processing, storage and distribution of fruit purees, juices and concentratesinfo:eu-repo/semantics/publishedVersio

Pasteurization of Beer by Non-Thermal Technologies

The pasteurization of beer occurs at the end of the industrial production, after fermentation. Generally, a mild thermal process (60°C) is employed aiming to inactivate the fermenting yeast and potential spoilage microorganisms, thus extending the beer shelf-life at room temperature. The heat treatment negatively affects the original beer freshness and flavor. In this study, beer pasteurization using emerging non-thermal technologies, namely, highpressure processing (HPP), pulsed electric fields (PEF), and ultrasound (US), was reviewed, including the effect on microbial inactivation and beer quality. The combination of non-thermal methods with mild heat for more efficient pasteurization of beer was also reviewed. All technologies caused microbial inactivation in beer. However, room temperature HPP treatment was the most efficient method, delivering the minimum 15 PU (pasteurization units) to beer after seconds (e.g., 300 MPa for 27 s), as opposed to thermal and TS treatments which required several minutes, while causing a negative impact on beer sensory. As expected, PEF + heat caused a higher microbial inactivation than PEF alone, and yeast ascospores were more resistant than vegetative yeast cells. Non-thermal PEF (35–45 kV/cm) caused 3–5.8 log reductions in vegetative bacteria. Studies on thermal assisted PEF and ultrasound combined with low heat (50–55°C) showed processing times in the magnitude of microseconds for PEF pasteurization and 0.5–2min (depending on the temperature) for TS pasteurization. With respect to impact of these technologies on beer quality, HPP, thermosonication (TS), high pressure homogenization (HPH), and dense phase CO2 (DPCD) treatments revealed less effect on beer sensory properties, better retaining the freshness of original beer, compared to thermally processed beers.info:eu-repo/semantics/publishedVersio

Emerging Non-Thermal Technologies as Alternative to SO2 for the Production of Wine

ReviewSO2 is an antioxidant and selective antimicrobial additive, inhibiting the growth of molds in the must during the early stages of wine production, as well as undesirable bacteria and yeasts during fermentation, thus avoiding microbial spoilage during wine production and storage. The addition of SO2 is regulated to a maximum of 150–350 ppm, as this chemical preservative can cause adverse effects in consumers such as allergic reactions. Therefore, the wine industry is interested in finding alternative strategies to reduce SO2 levels, while maintaining wine quality. The use of non-thermal or cold pasteurization technologies for wine preservation was reviewed. The effect of pulsed electric fields (PEF), high pressure processing (HPP), power ultrasound (US), ultraviolet irradiation (UV), high pressure homogenization (HPH), filtration and low electric current (LEC) on wine quality and microbial inactivation was explored and the technologies were compared. PEF and HPP proved to be effective wine pasteurization technologies as they inactivate key wine spoilage yeasts, including Brettanomyces, and bacteria in short periods of time, while retaining the characteristic flavor and aroma of the wine produced. PEF is a promising technology for the beverage industry as it is a continuous process, requiring only microseconds of processing time for the inactivation of undesirable microbes in wines, with commercial scale, higher throughput production potentialinfo:eu-repo/semantics/publishedVersio

Non-Thermal Processing of a Protein Functional Beverage Using Pulsed Electric Fields: Escherichia coli Inactivation and Effect on Proteins

The application of pulsed electric fields (PEFs) for the inactivation of Escherichia coli, suspended in a protein shake beverage and diluted with sterilized distilled water was carried out. Square bipolar pulses in the range of 25–40 kV/cm electric field intensities were applied at different frequencies (400–900 Hz) to investigate the effect of different PEF conditions on the microbial population and proteins relevant to this functional beverage. The treatment temperature was kept below the lethal temperature of the microorganism under investigation. As power consumption plays an important role in the efficiency of the PEF application, the dissipated power was also estimated. Four log reductions in the E. coli population were obtained with 10 pulses at a 40 kV/cm field intensity and 25 pulses at a 25 kV/cm field intensity. PEF-treated whey-protein concentrates showed less denaturation in proteins than thermally treated concentrates, especially for lower electric field intensities (0% denaturation ± 0.007 at 25 kV/cm and 900 Hz, 4.41% denaturation ± 0.008 at 40 kV/cm and 400 Hz). Soy protein isolates manifested high sensitivity to PEF processing and resulted in denaturation and aggregation in the protein structure.info:eu-repo/semantics/publishedVersio

Non-thermal high pressure processing, pulsed electric fields and ultrasound preservation of five diffeernt table wines

Wine preservation by alternative non-thermal and physical methods including high pressure processing (HPP), pulsed electric fields (PEF) and power ultrasound (US) technologies was investigated. The effect of these technologies on some quality parameters of five table wines was determined directly after processing and two months storage. For each wine, the pH, colour density, total phenolic content and antioxidant activity quality parameters were determined and the different treatments were compared. The pH of the untreated and treated wines generally remained unchanged after processing and storage. The antioxidant activity of the wines decreased after processing and storage. Generally, non-thermal processing did not affect the wine quality parameters during the 2 months storage. Overall, this study demonstrated that HPP had the smallest effect on the quality parameters assessed in five different winesinfo:eu-repo/semantics/publishedVersio