High‐pressure homogenization: a non‐thermal process applied for inactivation of spoilage microorganisms in beer

The inactivation of spoilage microorganisms in beer using high‐pressure homogenization (HPH) was studied with the aim of evaluating the possibility of changing the conventional pasteurization process using this particular process. The homogenization pressure required for the inactivation of lactic acid bacteria, acetic bacteria and yeasts was investigated. For the most resistant microorganisms, the pressure inactivation kinetics and the effects of multiple process passes, initial temperature of the beer and the CO₂ concentration were studied. The results indicated that Lactobacillus delbrueckii was the most resistant microorganism tested, requiring 250 MPa to reach a six decimal reduction. Additionally, results showed that L. delbrueckii inactivation followed a second‐order kinetic process. A multi‐pass process and the use of a high initial beer temperature increased inactivation by HPH with L. delbrueckii, allowing the use of 150 MPa to achieve a five log cycle of inactivation. In contrast, a high CO₂ concentration reduced the efficacy of the HPH process. The results that were obtained are useful for high‐pressure homogenization applications in breweries and help to elucidate the effect of this new technology in a beverage that is both alcoholic and carbonated. Copyright © 2013 The Institute of Brewing & Distilling     

High hydrostatic pressure inactivation of vegetative microorganisms, aerobic and anaerobic spores in pork Marengo, a low acidic particulate food product

To prolong the shelf-life of particulate food products, high pressure processing is one of the emerging technologies to be studied as an alternative to classical pasteurization and sterilization by heat. Pork Marengo (a low acidic, partially prepared stew of pieces pork, carrots and peas) was inoculated with several strains of sporulating and vegetative microorganisms. The microbial spoilage of the product was evaluated after a high pressure treatment of 400 MPa during 30 min at, respectively, 20 and 50 °C. Several Clostridium spp. and Bacillus spp. survived the treatment, and the Gram-positive cocci Enterococcus faecalis and Staphylococcus aureus were revealed to be more pressure resistant than Saccharomyces cerevisiae and the Gram-negative bacteria Pseudomonas fluorescens and Escherichia coli. The high pressure treatment at 20 °C demonstrated that high pressure processing (HPP) of neutral-pH foods cannot rely on pressure alone as a pasteurization/sterilization process. Another physical agent like heat is needed. High pressure treatment at 50 °C demonstrated that heat transfer limitations in particulate food products still can trouble their successful pasteurization/sterilization.     

超高压低酸性罐头中腐败菌的致死特性

研究了超高压对低酸性莴笋罐头中腐败菌的致死特性。采用超高压处理制备低酸性莴笋罐头,从腐败的罐头中自行筛选出6株耐压腐败菌,经鉴定为枯草芽孢杆菌和地衣芽孢杆菌。结合低酸性罐头中常采用的嗜热脂肪芽孢杆菌和致黑梭状芽孢杆菌两种指示菌,在300-500MPa的条件下比较了以上4种菌的耐压性,结果显示地衣芽孢杆菌更耐压,可作为低酸性食品超高压处理的对象菌,为超高压技术生产低酸性食品奠定了理论基础。     

Dry-pasteurization of egg albumen powder in a fluidized bed. II. Effect on functional properties: gelation and foaming

Dry‐pasteurization of egg albumen (EA) powder in a fluidized bed was studied in two experiments. Experiment 1 consisted of two different temperatures (90 and 130 °C) and experiment 2 of two air moisture levels (high and low). Powders were processed from 10 min to 3 h. The reference treatment was traditional pasteurization at 90 °C for 21 h. The fluidized bed treatment effects on gel texture, water‐holding capacity (WHC), protein binding, gel colour, foaming capacity, foam stability and surface pressure were evaluated. Gels of EA powders treated at high temperature and high air moisture levels exhibited higher stress, strain and WHC values than gels of untreated EA powder. The gel colour became significantly darker, greener and less yellow by fluidized bed treatment. Foaming and surface activity properties were un‐affected by the treatments, however, foam stability against liquid drainage correlated positively with surface pressure.     

Effects of high‐pressure processing on fungi spores: Factors affecting spore germination and inactivation and impact on ultrastructure

Food contamination with heat‐resistant fungi (HRF), and their spores, is a major issue among fruit processors, being frequently found in fruit juices and concentrates, among other products, leading to considerable economic losses and food safety issues. Several strategies were developed to minimize the contamination with HRF, with improvements from harvesting to the final product, including sanitizers and new processing techniques. Considering consumers’ demands for minimally processed, fresh‐like food products, nonthermal food‐processing technologies, such as high‐pressure processing (HPP), among others, are emerging as alternatives to the conventional thermal processing techniques. As no heat is applied to foods, vitamins, proteins, aromas, and taste are better kept when compared to thermal processes. Nevertheless, HPP is only able to destroy pathogenic and spoilage vegetative microorganisms to levels of pertinence for food safety, while bacterial spores remain. Regarding HRF spores (both ascospores and conidiospores), these seem to be more pressure‐sensible than bacterial spores, despite a few cases, such as the ascospores of Byssochlamys spp., Neosartorya spp., and Talaromyces spp. that are resistant to high pressures and high temperatures, requiring the combination of both variables to be inactivated. This review aims to cover the literature available concerning the effects of HPP at room‐like temperatures, and its combination with high temperatures, and high‐pressure cycling, to inactivate fungi spores, including the main factors affecting spores’ resistance to high‐pressure, such as pH, water activity, nutritional composition of the food matrix and ascospore age, as well as the changes in the spore ultrastructure, and the parameters to consider regarding their inactivation by HPP.     

Microbiological Aspects Related to the Feasibility of PEF Technology for Food Pasteurization

Processing unit operations that seek to inactivate harmful microorganisms are of primary importance in ascertaining the safety of food. The capability of pulsed electric fields (PEF) to inactivate vegetative cells of microorganisms at temperatures below those used in thermal processing makes this technology very attractive as a nonthermal pasteurization process for the food industry. Commercial exploitation of this technology for food pasteurization requires the identification of the most PEF-resistant microorganisms that are of concern to public health. Then, the treatment conditions applicable at industrial scale that would reduce the population of these microorganisms to a level that guarantees food safety must be defined. The objective of this paper is to critically compile recent, relevant knowledge with the purpose of enhancing the feasibility of using PEF technology for food pasteurization and underlining the required research for designing PEF pasteurization processes.     

Characterization of Bacterial Cellulose by Gluconacetobacter hansenii CGMCC 3917

In this study, comprehensive characterization and drying methods on properties of bacterial cellulose were analyzed. Bacterial cellulose was prepared by Gluconacetobacter hansenii CGMCC 3917, which was mutated by high hydrostatic pressure (HHP) treatment. Bacterial cellulose is mainly comprised of cellulose Iα with high crystallinity and purity. High‐water holding and absorption capacity were examined by reticulated structure. Thermogravimetric analysis showed high thermal stability. High tensile strength and Young's modulus indicated its mechanical properties. The rheological analysis showed that bacterial cellulose had good consistency and viscosity. These results indicated that bacterial cellulose is a potential food additive and also could be used for a food packaging material. The high textural stability during freeze–thaw cycles makes bacterial cellulose an effective additive for frozen food products. In addition, the properties of bacterial cellulose can be affected by drying methods. Our results suggest that the bacterial cellulose produced from HHP‐mutant strain has an effective characterization, which can be used for a wide range of applications in food industry.     

高压CO2技术杀菌灭酶效果及其机理研究进展

CO2具有独特的理化性质和经济性,在食品工业中得到了广泛的应用。高压CO2技术作为一种新型的非热力杀菌技术引起了重视,本文主要介绍了高压CO2技术对微生物的杀灭效果和对酶钝化作用的研究进展及其相关机理。     

Intervention Technologies for Ensuring Microbiological Safety of Meat: Current and Future Trends

Abstract: This article reviews current and future techniques that are applied in the meat industry to ensure product safety. Consumer demand for high‐quality food and raised economic standards have triggered the development of emergent technologies to replace traditional well‐established preservation processes. Some promising nonthermal and thermal technologies, such as chemical and biological interventions, high hydrostatic pressure (HHP), irradiation, active packaging, natural antimicrobials and microwave, radiofrequency, and steam pasteurization, are under consideration for the preservation of meat products. All these alternative technologies are designed to be mild, energy‐conserving, environmentally friendly, and maintaining natural appearance and flavor, while eliminating pathogens and spoilage microorganisms. Their combination, as in the hurdle theory, may improve their effectiveness for decontamination. The objective of this article is to reflect on the possibilities and especially the limitations of the previously mentioned technologies.     

High Hydrostatic Pressure Processing of Fruit and Vegetable Products

High hydrostatic pressure (HHP) as a minimal thermal technology is a valuable tool for microbiologically safe and shelf-stable fruit and vegetable production. Microorganisms and deteriorative enzymes can be inhibited or inactivated depending on the amount of pressure and time applied to the product. The resistance of microorganisms and enzymes to pressure in fruit and vegetable products also is dependent on both the type and the amount of enzymes or microorganisms as well as food composition. While on one hand, microorganisms (other than spores) can be inactivated at mild pressures (< 300 MPa), on the other, enzymes can be very resistant to pressure and their resistance may increase when isolated forms are pressurized. Nevertheless, microbiologically safe fruit and vegetable products can be obtained without change in flavor if temperature is not increased beyond pasteurization temperatures. The remaining enzyme activity in HHP processed fruit and vegetable products can be delayed if a combination of obstacles, such as refrigeration temperatures, low pH, and antibrowning agents, are used to increase the shelf life of these types of products. Therefore, HHP is a promising minimal thermal technology that can be used to deliver more variety of less processed fruit and vegetable products than consumers are demanding today.     

二氧化碳杀菌技术研究进展

二氧化碳具有化学惰性、无腐蚀性、高挥发性等独特理化性质及经济性,在食品加工业得到广泛应用;二氧化碳在果蔬、肉制品、谷物、液体食品中保鲜作用已有相关研究,近年研究发现,高压和超临界状态二氧化碳能抑制微生物生长,已成为非热力杀菌方法的一个研究热点。该文主要介绍二氧化碳杀菌机理及其应用。     

Effect of High Pressure Homogenization and Dimethyl Dicarbonate (DMDC) on Microbial and Physicochemical Qualities of Mulberry Juice

In this study, the effect of high pressure homogenization (HPH) and dimethyl dicarbonate (DMDC) on microbial and nutrient qualities of mulberry juice was evaluated. Results showed that repeated HPH passes at 200 MPa or adding DMDC at 250 mg/L significantly inactivated the indigenous microorganisms in mulberry juice (P < 0.05), whereas some surviving microorganisms recovered to grow during storage of 4 °C. The combined treatment with 3 passes of HPH and 250 mg/L of DMDC (HPH‐DMDC) decreased the population of surviving indigenous microorganisms to the level attained by heat treatment at 95 °C for 1 min (HT) with no significant increase (P > 0.05) in the population of microorganisms during subsequent storage at 4 °C. Moreover, no significant changes (P > 0.05) in the physical attributes, including pH, TSS (^oBrix), L*, a*, and b* values were observed in the samples treated by the HPH‐DMDC or by HT. Compared with HT, HPH‐DMDC treatment resulted in a higher degree of retention in total phenolics, and α‐glucosidase inhibitory activity, although the treatment led to higher losses in cyanidin 3‐glucoside, cyanidin 3‐rutinoside, and antioxidant capacity. Overall, HPH‐DMDC treatment can be a useful alternative to conventional thermal pasteurization of mulberry juice, considering its ability to inactive, and inhibit indigenous microorganisms.     

Recent Advances in Food Processing Using High Hydrostatic Pressure Technology

High hydrostatic pressure is an emerging non-thermal technology that can achieve the same standards of food safety as those of heat pasteurization and meet consumer requirements for fresher tasting, minimally processed foods. Applying high-pressure processing can inactivate pathogenic and spoilage microorganisms and enzymes, as well as modify structures with little or no effects on the nutritional and sensory quality of foods. The U.S. Food and Drug Administration (FDA) and the U.S. Department of Agriculture (USDA) have approved the use of high-pressure processing (HPP), which is a reliable technological alternative to conventional heat pasteurization in food-processing procedures. This paper presents the current applications of HPP in processing fruits, vegetables, meats, seafood, dairy, and egg products; such applications include the combination of pressure and biopreservation to generate specific characteristics in certain products. In addition, this paper describes recent findings on the microbiological, chemical, and molecular aspects of HPP technology used in commercial and research applications.     

Nonthermal pasteurization of liquid foods using high‐intensity pulsed electric fields

Processing foods with high‐intensity pulsed electric fields (PEF) is a new technology to inactivate microorganisms and enzymes with only a small increase in food temperature. The appearance and quality of fresh foods are not altered by the application of PEF, while microbial inactivation is caused by irreversible pore formation and destruction of the semipermeable barrier of the cell membrane. High‐intensity PEF provides an excellent alternative to conventional thermal methods, where the inactivation of the microorganisms implies the loss of valuable nutrients and sensory attributes. This article presents recent advances in the PEF technology, including microbial and enzyme inactivation, generation of pulsed high voltage, processing chambers, and batch and continuous systems, as well as the theory and its application to food pasteurization. PEF technology has the potential to improve economical and efficient use of energy, as well as provide consumers with minimally processed, microbiologically safe, nutritious and freshlike food products.     

E: Food Engineering & Physical Properties. Effect of Supercritical Carbon Dioxide Pasteurization on Natural Microbiota,Texture, and Microstructure of Fresh‐Cut Coconut

Abstract: The objective of the present study was the evaluation of the effectiveness of supercritical carbon dioxide (SC‐CO₂) as a nonthermal technology for the pasteurization of fresh‐cut coconut, as an example of ready‐to‐eat and minimally processed food. First, the inactivation kinetics of microbiota on coconut were determined using SC‐CO₂ treatments (pressures at 8 and 12 MPa, temperatures from 24 to 45 °C, treatment times from 5 to 60 min). Second, the effects of SC‐CO₂ on the hardness and microstructure of fresh‐cut coconut processed at the optimal conditions for microbial reduction were investigated. SC‐CO₂ treatment of 15 min at 45 °C and 12 MPa induced 4 log CFU/g reductions of mesophilic microorganisms, lactic acid bacteria, total coliforms, and yeasts and molds. The hardness of coconut was not affected by the treatment but the samples developed an irregular and disorderly microstructure. Results suggested the potential of SC‐CO₂ in preserving fresh‐cut fruits and ready‐to‐eat products. Practical Application: The effectiveness of SC‐CO₂ as a nonthermal technology for the pasteurization of fresh‐cut coconut was studied. The results demonstrated the possibility to apply the treatment as a method to induce the inactivation of the natural microorganisms, preventing the microbial spoilage and, at the same time, preserving the hardness of the product. The available data will give a valuable input to the fresh‐cut fruits industry.     

Effects of High Hydrostatic Pressure Processing on Hen Egg Compounds and Egg Products

High hydrostatic pressure (HHP), used alone or with other processes, is an emerging technology increasingly used in the food industry to improve microbial safety, and the functionality and bioactive properties of food products. HHP provides a way to reduce energy requirements for food processing and may contribute to improved energy efficiency in the food industry. Hen egg is used by the food industry to formulate many food products. To improve the microbiological safety of egg and egg‐derived products, HHP processing is an attractive alternative to heat‐ pasteurization and a potential technology. However, HHP treatment induces structural modifications of egg components (such as proteins) which could positively or negatively affect the physicochemical and functional properties of egg‐derived products. Improving our knowledge regarding the potential of HHP in the egg industry will add value to the final food products and increase profitability for egg producers and the food industry.     

高压食品加工技术及在乳制品中的应用

介绍了高压加工技术在食品方面应用的研究进展，其内容有：高压原理，装备和对微生物，蛋白质，酶的影响，高压乳及其制品的研究，作为国际热门食品加工方法的高压处理技术必将成为２１世纪崭新的食品加工技术，在开发新产品方面有着广泛的应用前景。     

Comparing the Effects of Ultra‐High‐Pressure Homogenization and Conventional Thermal Treatments on the Microbiological,Physical, and Chemical Quality of Almond Beverages

The effects of ultra‐high‐pressure homogenization (UHPH) at 200 and 300 MPa, in combination with different inlet temperatures (55, 65, and 75 °C) on almond beverages with lecithin (AML) and without lecithin (AM), were studied. UHPH‐treated samples were compared with the base product (untreated), pasteurized (90 °C, 90 s), and ultra‐high‐temperature (UHT, 142 °C, 6 s) samples. Microbiological analysis, physical (dispersion stability, particle size distribution, and hydrophobicity), and chemical (hydroperoxide index) parameters of special relevance in almond beverages were studied. Microbiological results showed that pressure and inlet temperature combination had a significant impact on the lethal effect of UHPH treatment. While most UHPH treatments applied produced a higher quality of almond beverage than the pasteurized samples, the combination of 300 MPa and 65 and/or 75 °C corresponded to a maximum temperature after high pressure valve of 127.7 ± 9.7 and 129.3 ± 12.6 °C, respectively. This temperature acted during less than 0.7 s and produced no bacterial growth in almond beverages after incubation at 30 °C for 20 d. UHPH treatments of AML samples caused a significant decrease in particle size, resulting in a high physical stability of products compared to conventional heat treatments. UHPH treatment produced higher values of hydroperoxide index at day 1 of production than heat‐treated almond beverage. Hydrophobicity increased in AML‐UHPH‐treated samples compared to AM and conventional treatments. Practical Application: Ultra‐high‐pressure‐homogenization (UHPH) is an emerging technology, a potential alternative to conventional heat treatments. It is a simple process consisting of single step. When liquid food (almond beverage in this study) passes through the high‐pressure valve, a very good stability and reduction of microorganisms is achieved, both effects due to the particle breakdown. Specific UHPH conditions could produce commercial sterilization of almond beverage.     

Thermal pasteurization requirements for the inactivation of Salmonella in foods

Thermal processing is still one of the most effective methods for inactivating undesirable microorganisms in foods. Heat is used to inactivate pathogens and in developing typical flavours, aromas, texture and colour of a cooked food. Pasteurization produces safer foods with longer shelf-life. Since mild temperatures are applied for a specified time, complementary food preservation techniques such as modified atmospheres, addition of preservatives or the use of refrigerated storage and distribution, might be needed to control the growth of the surviving microorganisms. This review starts by addressing food contamination by Salmonella spp., referring to some examples of outbreaks, and the benefits of pasteurization in terms of Salmonella inactivation. A section covering the thermal resistance studies of Salmonella in poultry and other animal-based foods is presented. Based on Salmonella thermal resistance data, minimum pasteurization times are suggested at different heating temperatures, to meet the guidelines and recommendations of governmental food agencies for meat products (7 log reduction). Validation of a minimum pasteurization time must be done for each specific food-thermal process, by inserting a thermocouple into the “coldest” spot of the food , and ensuring that this point is submitted to the minimum pasteurization value required. This procedure will guarantee food safety with respect to Salmonella. Salmonella pasteurization requirements of low moisture foods such as some nuts, chocolate and peanut butter are also reviewed.     

超高压升/卸压过程对杀菌效果的影响研究进展

相比传统食品热杀菌技术,超高压杀菌技术不仅能达到良好的杀菌效果,还能保持食品原有的颜色、风味、营养等品质。为了保证超高压杀菌的可靠性与安全性,就需要对影响超高压杀菌效果的因素进行研究。以往的研究主要集中在压力、保压时间及温度等方面等因素,然而,一系列研究表明,超高压升/卸压过程也会影响杀菌效果。本文介绍了影响超高压杀菌效果的主要因素,重点介绍升/卸压过程对杀菌的影响,以期推进超高压杀菌技术在我国食品加工领域的应用。