Continuous-Flow UV Liquid Food Pasteurization: Engineering Aspects

Ultraviolet (UV)-C treatments are a promising technology for liquid food pasteurization as an alternative to heat treatments. However, the design of efficient UV reactors to reduce pertinent microorganisms and comply with current food safety goals is still an engineering challenge due to the low penetration depth of UV light in liquid foods with high UV absorbance and suspended particles, and the variations in the residence time of the product in the UV reactors. This review focuses on physical aspects of UV radiation related to the essential product and processing parameters for the design of UV reactors. The UV equipment available for liquid food processing is described and the main drawbacks and advantages are discussed.     

Pulsed Light Treatments for Food Preservation. A Review

Consumers demand high-quality processed foods with minimal changes in nutritional and sensory properties. Nonthermal methods are considered to keep food quality attributes better than traditional thermal processing. Pulsed light (PL) is an emerging nonthermal technology for decontamination of food surfaces and food packages, consisting of short time high-peak pulses of broad spectrum white light. It is considered an alternative to continuous ultraviolet light treatments for solid and liquid foods. This paper provides a general review of the principles, mechanisms of microbial inactivation, and applications of PL treatments on foods. Critical process parameters that are needed to be optimized for a better efficiency of PL treatments are also discussed. PL has considerable potential to be implemented in the food industry. However, technological problems need to be solved in order to avoid food overheating as well as to achieve better penetration and treatment homogeneity. In addition, a more extensive research is needed to understand how PL affects quality food attributes.     

Quality analysis,classification, and authentication of liquid foods by near-infrared spectroscopy: A review of recent research developments

Nowadays, near-infrared spectroscopy (NIR) has become one of the most efficient and advanced techniques for analysis of food products. Many relevant researches have been conducted in this regard. However, no reviews about the applications of NIR for liquid food analysis are reported. Therefore, this review summarizes the recent research developments of NIR technology in the field of liquid foods, focusing on the detection of quality attributes of various liquid foods, including alcoholic beverages (red wines, rice wines, and beer), nonalcoholic beverages (juice, fruit vinegars, coffee beverages, and cola beverages), dairy products (milk and yogurt), and oils (vegetable, camellia, peanut, and virgin olive oils and frying oil). In addition, the classification and authentication detection of adulteration are also covered. It is hoped that the current paper can serve as a reference source for the future liquid food analysis by NIR techniques.     

Inactivation of carboxypeptidase A and trypsin by UV–visible light

In the present work, the effect of UV–visible irradiation on the activity of carboxypeptidase A, and trypsin enzymes is shown. The irradiation of the above-mentioned enzymes inhibits their activity, in such a way that sufficiently high irradiation times annul their catalytic action. For carboxypeptidase A a total inactivation after 20 min of irradiation is observed, while trypsin is inactivated completely after 12 min of irradiation. Fitting the data to the Lineweaver–Burk graphs shows that, in the case of CPA enzyme, the inhibition caused by irradiation is similar to that of uncompetitive type. For trypsin, the irradiation acts similarly to a mixed inhibition-type.

Industrial relevance

UV irradiation is a technology used in food treatment, since it has been shown to be effective in the destruction of microorganisms. It can also be applied in the sterilization of enzymatic preparations used in the food industry, but it can have harmful effects, since it can go so far as to inactivate some of the enzymes. In some cases it interests to inactivate enzymes, and it is for it that this treatment type can be effective. In other cases it interests that the enzymes remain active. This way, it will be necessary to avoid that they are exposed to the light.     

紫外发光二极管（UV-LED）技术对食品微生物灭活应用的研究进展

紫外辐照是一种非热杀菌技术,汞蒸气紫外灯是现阶段用于食品卫生处理的主要设备,但受某些因素影响,汞灯的生产使用将逐渐变少,被环保节能的紫外发光二极管（UV-LED）取代是一种不可避免的趋势。本文根据UV-LED发光原理和多波长耦合应用的特点,综述了对微生物灭活的机理、探究了影响灭活效果的因素（波长、紫外剂量和物料特性）、处理食品的灭菌效果以及对部分食品品质的影响,为UV-LED在食品领域的杀菌处理工艺和设备参数优化提供参考。     

脉冲电场在固体食品加工中的应用

脉冲电场(pulsed electric field, PEF)技术被视为21世纪食品非热加工技术发展史上的里程碑之一。迄今为止, PEF已广泛应用于果汁、牛奶和液态蛋等液体食品的杀菌和钝酶,并朝着商业化道路前进。然而,与PEF在液体食品中的应用相比,其在固体食品中的应用还处于起步阶段。固体食品的表面虽然也富含微生物,但PEF处理这类食品对微生物的影响较小,因此不能将其应用于固体食品的杀菌保鲜。仅管如此, PEF诱导的细胞电穿孔使其可作为一种预处理方法 ,通过增加质量和能量传递效率的方式来进行辅助固体食品的干燥、冻融、烹饪等。因此,本文重点介绍基于PEF细胞响应的高品质食品加工应用,总结PEF处理室的特点及PEF预处理固体食品的相关机制。最后,本文探讨了PEF在固体食品加工中的主要障碍和前景,为PEF未来在食品行业的发展拓宽研究方向。     

Ultraviolet inactivation kinetics of Escherichia coli and Yersinia pseudotuberculosis in annular reactors

Terrorist threats have precipitated the need for information on the ultraviolet (UV) resistance of potential biothreat agents in food processing, such as Yersinia pestis. The objective of this study was to characterize the resistance of the Yersinia species to UV treatment using a single-lamp annular UV reactor. A novel method is proposed to measure the inactivation kinetics of Yersinia pseudotuberculosis, a surrogate of Y. pestis. This proposed method can overcome the disadvantages of the traditional collimated beam approach for liquids with high absorptive properties, such as liquid foods. As a reference, an inactivation rate of Escherichia coli K12 in caramel model solutions was measured first. Both first-order and series-event inactivation models were used to fit UV inactivation data. For the series-event model, an inactivation constant of k(SE)= 0.675 cm(2)/mJ and threshold n= 4 were obtained for E. coli K12 with the coefficient of determination R(2)= 0.987 and the standard deviation of log(10) reductions sigma(y)= 0.133. For Y. pseudotuberculosis, k(SE)= 0.984 cm(2)/mJ and n= 3 were obtained with R(2)= 0.972 and sigma(y)= 0.212. In contrast, for the first-order inactivation model, the first-order inactivation constant k(1)= 0.325 cm(2)/mJ with R(2)= 0.907 and sigma(y)= 0.354 was found for E. coli; and k(1)= 0.557 cm(2)/mJ with R(2)= 0.916 and sigma(y)= 0.402 was obtained for Y. pseudotuberculosis. Based on R(2), sigma(y), and the maximum absolute and relative errors, the series-event inactivation model describes the UV inactivation kinetics of Y. pseudotuberculosis and E. coli better than the first-order model. It is apparent that Y. pseudotuberculosis is less resistant to UV light than E. coli K12.     

Pulsed Light Treatment of Different Food Types with a Special Focus on Meat: A Critical Review

Today, the increasing demand for minimally processed foods that are at the same moment nutritious, organoleptically satisfactory, and free from microbial hazards challenges the research and development to establish alternative methods to reduce the level of bacterial contamination. As one of the recent emerging nonthermal methods, pulsed light (PL) constitutes a technology for the fast, mild, and residue-free surface decontamination of food and food contact materials in the processing environment. Via high frequency, high intensity pulses of broad-spectrum light rich in the UV fraction, viable cells as well as spores are inactivated in a nonselective multi-target process that rapidly overwhelms cell functions and subsequently leads to cell death. This review provides specific information on the technology of pulsed light and its suitability for unpackaged and packaged meat and meat products as well as food contact materials like production surfaces, cutting tools, and packaging materials. The advantages, limitations, risks, and essential process criteria to work efficiently are illustrated and discussed with relation to implementation on industrial level and future aspects. Other issues addressed by this paper are the need to take care of the associated parameters such as alteration of the product and utilized packaging material to satisfy consumers and other stakeholders.     

A review of kinetic models for inactivating microorganisms and enzymes by pulsed electric field processing

As a non-thermal technology, pulsed electric field (PEF) treatment can be utilized in food processing and bioengineering for the inactivation of microorganisms and quality-degrading enzymes, as well as the retention of health-related compounds and the extension of shelf-life. Development of kinetic models that fit the degree of microbial inactivation and the loss of food quality is important to improve the efficiency of PEF treatment. The current review aims to provide an overview of the kinetic models used by PEF for microbial inactivation in liquid foods. Kinetics modeling for the destruction of microorganisms, inactivation of enzymes, retention of health-related compounds, and extension of shelf-life are discussed. Additionally, the fitting accuracy of several models, as well as issues that need further investigation, are discussed to promote further understanding and the deployment of PEF technology.     

Biological Aspects in Food Preservation by Ultraviolet Light: a Review

The potential to commercialize nonthermal ultraviolet (UV) light technologies as new methods for preserving food products has caught the attention of a food industry that wishes to fulfill consumers' demands for fresh products. Numerous investigations have demonstrated UV light's ability to inactivate a wide range of microorganisms. However, the lack of UV sensitivity data from pathogenic and spoilage bacteria is evident. In addition, the main factors associated with UV light in terms of microbial lethality remain unclear. This review surveys critical factors (process, microbial, and environmental parameters) that determine UV microbial resistance and assess the effects of such factors on the inactivation mechanism and repair pathway efficiency. The effects of some of these factors, such as prior sublethal stresses and post-recovery conditions of UV treatments, may extensively improve the damage repair capacity and thus microbial survivability. Further research is needed to establish adequate control measures pre- and post-UV treatments. Furthermore, the possibility of combining UV light with conventional preservatives and other nonthermal technologies was assessed. The combination of UV light with mild heating or oxidant compounds could offer promising treatments to enhance the safety and stability of minimally processed foods.     

FACTORS AFFECTING THE ULTRAVIOLET INACTIVATION OF ESCHERICHIA COLI K12 IN APPLE JUICE AND A MODEL SYSTEM*

Ultraviolet (UV) light has been used successfully for years to sterilize water and was recently approved as an acceptable irradiation treatment for the processing of juice. Although there is considerable information on the efficacy of UV processing in the treatment of water, limited data are available on its efficacy in fluid food systems. The objectives of this work were to determine the effects of apple‐juice properties on the UV inactivation of Escherichia coli K12 and the interdependence of intensity and time on the efficacy of UV light. Results showed that absorbance (A) and suspended solids (SS) affected UV inactivation, while pH and dissolved solids did not. Concerning the interdependence of intensity and time, intensity levels can only be changed without sacrificing effectiveness at a limited range of intensity and dose levels. This means that the range of the intensity level of the actual UV reactor must be considered in process‐parameter determination.     

Food processing by pulsed electric fields. II. Biological aspects

Abstract

Investigations on the biological effects of high voltage electric pulses primarily concern membrane permeabilization and microbial inacti‐vation. Electroporation resulting from increased transmembrane potential is probably the main cause for membrane permeabilization. Equations are presented for this phenomenon. Results from several studies on the inactivation of microorganisms by pulsed electric fields are summarized in tables that relate the rate of inactivation to process conditions. The influence of three sets of parameters is discussed: 1) type and physiological state of the microorganism; 2) chemical composition and electrical resistivity of the microorganism‐containing food or medium; 3) process conditions such as field intensity, duration and number of pulses, dissipated energy, final temperature, type of pulse and of treatment chamber. Data can be used to select conditions which produce a 5–6 log cycle inactivation for many yeasts or vegetative bacteria. Bacterial spores generally resist inactivation. Pulsed electric fields of relatively low intensity may be used to permeabilize larger cells from plant or animal tissues in order to facilitate theextraction of specific constituents or to increase the drying rate. Little is known concerning the possible chemical or physico‐chemical modifications of food constituents by high voltage electric pulses. Some enzymes appear to be inactivated, even at low temperatures, while others are more resistant. The sensorial characteristics of a number of foods subjected to electric fields do not appear to be significantly altered. Potential food applications are numerous and mainly related to liquid foods (fruit juices, milk, sauces, liquid egg) or to pumpable food pastes (fruit or vegetable purées, minced meat, etc.). Both neutral and acidic foods are likely candidates. The main objectives of microbial inactivation by electric pulses are food sanitation and/or extension of chilled storage. The process should be nonthermal (maximum ?T of ～30°C) to preserve food freshness and quality. A low operating cost, estimated at 0.4–0.8 US cents per liter of food (capital investment not included) and continuous operation at high flow rate (>1000 L/h) represent significant industrial advantages for this new technology.     

UV-C inactivation of Escherichia coli at different temperatures

The influence of treatment parameters (dose and temperature), treatment medium characteristics (absorption coefficient, pH and water activity) and microbiological factors (strain, growth phase and UV damage and repair capacity) on Escherichia coli UV-C resistance has been investigated. UV-C doses to inactivate at 25 °C 99.99% of the initial population (4D) of five strains of E. coli in McIlvaine buffer of pH 7.0 with tartrazine added (absorption coefficient of 10.77 cm⁻¹) were 16.60, 14.36, 14.36, 13.22, 11.18 J/mL for strains E. coli STCC 4201, STCC 471, STCC 27325, O157:H7 and ATCC 25922, respectively. The entrance in the stationary growth phase increased the 4D value of the most resistant strain, E. coli STCC 4201, from 13.09 to 17.23 J/mL. Survivors to UV treatments showed neither oxidative damages nor injuries in cell envelopes. On the contrary, the photoreactivation by the incubation of plates for 60 min below visible light (11.15 klx) increased the dose to 18.97 J/mL. The pH and the water activity of the treatment medium did not affect the UV tolerance of E. coli STCC 4201, but the lethal effect of the treatments decreased exponentially (Log₁₀4D = − 0.0628α + 0.624) by increasing the absorption coefficient (α). A treatment of 16.94 J/mL reached 6.35, 4.35, 2.64, 1.93, 1.63, 1.20, 1.02 and 0.74 Log₁₀ cycles of inactivation with absorption coefficients of 8.56, 10.77, 12.88, 14.80, 17.12, 18.51, 20.81 and 22.28 cm⁻¹. The temperature barely changed the UV resistance up to 50.0 °C. Above this threshold, inactivation rates due to the combined process synergistically increased with the temperature. The magnitude of the synergism decreased over 57.5 °C. An UV treatment of 16.94 J/mL in media with an absorption coefficient of 22.28 cm⁻¹ reached 1.23, 1.64, 2.36, 4.01 and 6.22 Log₁₀ cycles of inactivation of E. coli STCC 4201 at 50.0, 52.5, 55.5, 57.5 and 60.0 °C, respectively.

Industrial relevance

Results obtained in this investigation show that UV light applied at mild temperatures (57.5 to 60 °C) could be an alternative to heat treatments for 5-Log₁₀ reductions of E. coli in liquid foods. Since microbial resistance to UV-C light did not depend on the pH and water activity (a_w) of the treatment media, eventual advantages of UV light for pasteurization purposes will be higher in low a_w foods. E. coli STCC 4201 could be considered as a target when UV light processing of foods.     

叶绿素镁钠盐对液态食品中Staphylococcus aureus的光动力杀菌研究

以叶绿素镁钠盐为光敏剂,研究了其对几种液体食品中金黄色葡萄球菌的光动力杀菌效果。结果表明,叶绿素镁钠盐对几种液态食品中的金黄色葡萄球菌具有很强的杀菌效果,其中以10-5mol/L的叶绿素镁钠盐杀菌效果最佳,10 min金黄色葡萄球菌减少了4.5个对数;随着光照时间的延长,液态食品中的金黄色葡萄球菌的致死率明显增加,特别是在起始10 min内;一般透光性好的食品包装材料对液态食品中金黄色葡萄球菌光动力杀菌效率没有影响,但液态食品的pH对其杀菌效率有一定的影响。对于不同的液态食品,在澄清或酸性的食品中叶绿色镁钠盐的光动力杀菌效果较好,但当食品中含固体颗粒或较浑浊时,其杀菌效率显著降低。     

非热杀菌技术杀灭食品中芽孢效能及机理研究进展

传统热杀菌会对食品品质产生不利影响,造成食品颜色变化、产生异味、营养损失等不良后果;非热杀菌技术是食品工业新型加工技术,处理过程中可以保持相对较低的温度,对食品的色、香、味以及营养成分影响较小;同时有利于保持食品中各种功能成分的生理活性,可以满足消费者对高品质食品的要求。芽孢在加工过程中抗性强,在食品中萌发和生长的潜力较大,因此,利用低热或非热灭菌技术对芽孢进行灭活是当前食品工业面临的严峻挑战和重要课题。本文综述现有非热杀菌技术（如高静压技术、高压CO2技术、低温等离子体技术、紫外辐射技术、高压脉冲电场技术等）独立处理或与其他处理技术相结合对芽孢灭活的效果及其机理,着重讨论其在食品行业中的应用以及芽孢灭活的分子机制,以期为生产安全食品、减少不同种类食品中微生物污染提供解决方案。     

Viral Inactivation in Foods: A Review of Traditional and Novel Food‐Processing Technologies

ABSTRACT: Over one‐half of foodborne illnesses are believed to be viral in origin. The ability of viruses to persist in the environment and foods, coupled with low infectious doses, allows even a small amount of contamination to cause serious problems. An increased incidence of foodborne illnesses and consumer demand for fresh, convenient, and safe foods have prompted research into alternative food‐processing technologies. This review focuses on viral inactivation by both traditional processing technologies such as use of antimicrobial agents and the application of heat, and also novel processing technologies including high‐pressure processing, ultraviolet‐ and gamma‐irradiation, and pulsed electric fields. These industrially applicable control measures will be discussed in relation to the 2 most common causes of foodborne viral illnesses, hepatitis A virus and human noroviruses. Other enteric viruses, including adenoviruses, rotaviruses, aichi virus, and laboratory and industrial viral surrogates such as feline caliciviruses, murine noroviruses, bacteriophage MS2 and ΦX174, and virus‐like particles are also discussed. The basis of each technology, inactivation efficacy, proposed mechanisms of viral inactivation, factors affecting viral inactivation, and applicability to the food industry with a focus on ready‐to‐eat foods, produce, and shellfish, are all featured in this review.     

A numerical approach for predicting volumetric inactivation of food borne microorganisms in liquid substrates by pulsed light treatment

Pulsed light (PL) technology is able to effectively destroy a wide variety of food spoilage and pathogenic microorganisms. However, the effectiveness of PL treatment depends on direct exposure of the target microorganisms to the short, high energy pulses of light. The complex physical and chemical properties of foods affect the way light propagates through a given food substrate, and thus there is a real potential for insufficiently or non-uniformly treated products. The objective of this work was to develop a method for predicting levels and spatial distribution of microbial inactivation in PL treatment of liquid substrates, and to validate the predictions with experimental data. Three liquids with different composition and optical properties (BPB, TSB, apple juice) were inoculated with either Escherichia coli ATCC 25922 or Listeria innocua FSL C2-008 and treated with PL, in two different geometries. The Weibull model was used to describe the microbial inactivation kinetics for each organism. The kinetic equations were coupled with previously determined equations describing either the total fluence (F_total) or UV fluence (F_UV) distribution in each of the liquids, for either cylindrical or rectangular prismatic geometries. COMSOL simulation software was used to generate maps of spatial distribution of microbial inactivation and to predict the average volumetric inactivation for each substrate. The model that used F_total provided gross over-estimations for microbial inactivation, while using F_UV as the treatment dose yielded reasonably good predictions of microbial inactivation, especially for the more opaque and turbid substrates. This approach can help processors determine which substrates would be suitable for PL treatment, and to design highly effective and uniform PL treatments.     

Microbial Inactivation and Quality of Guava and Passion Fruit Nectars Treated by UV-C Light

Freshness attributes in food products continue to be a trend of relevance to consumers. UV-C light treatment of fluid foods is a non-thermal process potentially suitable to obtain high-quality fruit nectars. This study pursued to test the effect of UV-C light treatment on indigenous microorganisms and sensory quality of two tropical fruit nectars. Guava and passion fruit nectars were treated with light at λ = 253.7 nm up to 24 and 11 J/ml, respectively, in an annular reactor. The effects of this process on microbial inactivation were assessed by aerobic mesophilic count (AMC), yeast and mould count (YMC) and by triangle tests regarding sensory quality. Microbial inactivation increased with fluence. The highest fluence decreased AMC of guava and passion fruit nectars by 0.51 and 1.36 log colony-forming units (CFU) per millilitre, respectively, and YMC of guava by 0.53 log CFU/ml. However, the sensory panel detected differences due to treatments even at the lowest fluences (15 and 6 J/ml for guava and passion fruit, respectively). This work confirms the capability of UV light to inactivate microorganisms in fluid foods, but in sensitive products such as tropical fruit nectars, sensory changes may be a drawback for practical application of the technology for producing fresh-like stable products.     

Membrane concentration of liquid foods by forward osmosis: Process and quality view

The industrial thermal processing of foods may have a severe impact on the sensorial and nutritional properties of the final product. Membrane technologies have been extensively studied as alternative processes. Forward osmosis (FO) is a promising membrane technology to be used in food industries. The only driving force of the process is the osmotic pressure difference between the two solutions that flow in counter-current mode on opposite sides of a permeable membrane. Thus, the main advantages of FO, compared to both thermal and conventional membrane processing, include low hydraulic pressure, low treatment temperature, low fouling tendency, high solids content processing capability and easy scale-up. A detailed, up-to-date summary of potential FO applications for concentrating liquid foods is presented in this review article. The effect of the main process parameters on the filtration performance and their impact on the sensorial and nutritional factors of the final product are described and discussed for a broad spectrum of foods.     

Relationship between optical properties of beverages and microbial inactivation by intense pulsed light

This study determined the inactivation effects of the intense pulsed light (IPL) on Pseudomonas aeruginosa in various liquid foods and elucidated the relationship between microbial reduction and the optical properties of twelve liquid foods. In mineral water and isotonic beverage, 7.0 log reductions of P. aeruginosa were obtained with the IPL treatment at total fluence of 0.97 J/cm². At 12.17–24.35 J/cm², 7.0 log reductions were shown in five liquid samples (apple juice, carbonated beverages and plum juice), while only 0.5- to 2.0-log reductions were shown in the rest samples even after 29.21 J/cm² total fluence of the IPL treatment. High value of transmittance and low value of extinction coefficient have a decisive effect on the microbial inactivation because it allows the intensity of the IPL to be preserved as it penetrates into the sample. The best-fit regression kinetic which can explain the relationship between extinction coefficient and bactericidal effect was an exponential function.Industrial relevanceIntense pulsed light (IPL) is one of the nonthermal processing technologies for ensuring safe foods with satisfactory qualities. Through this study, transparent liquids showed a high microbial reduction level after IPL treatment in a short time. So it can be concluded that IPL has a potential as an excellent alternative or complement to conventional thermal processing of transparent liquids. Also, inactivation kinetic equation deducted from this study can be used to predict the microbial reduction level of specific liquid before IPL treatment by using its extinction coefficient.