Low thermal inactivation of Escherichia coli ATCC 25922 in pineapple,orange and watermelon juices: Effect of a prior acid‐adaptation and of carvacrol supplementation

Past research on the association of natural antimicrobials and low temperatures for fruit juices pasteurization has not targeted acid‐adapted strains which are yet the most relevant strains in these products. We found that previously acid‐adapted Escherichia coli ATCC 25922 cells exhibited an increase of their resistance to thermal inactivation at 55 °C for 5 min both in the presence and absence of carvacrol (30 µL/L). The inactivation of E. coli was more intense in pineapple (pH 3.25) and orange (pH 3.61) juice, than in watermelon juice (pH 5.4). Supplementation of juices with carvacrol decreased the survival of both acid‐adapted and non‐adapted bacterial cells. Our results suggest that the supplementation of fruit juices with natural antimicrobials, such as carvacrol, may contribute to counteract the mild thermal tolerance developed by acid‐adapted bacteria. Given the different properties of fruit juices, such combined treatments need to be developed specifically for each fruit product.

Practical applications

Supplementation of fruit juices with natural antimicrobials has been described to increase the efficiency of microbial mild thermal inactivation treatments. However, its effect on the thermal resistance of acid‐adapted cells has not previously been addressed. We observed that acid adaptation enhances mild thermal tolerance. Our results suggest that natural antimicrobials can effectively counteract the mild thermal tolerance of acid‐adapted cells. The combination of mild temperature treatments and natural antimicrobials is a firm alternative to conventional pasteurization to ensure the safety of fruit juices without affecting their nutritional properties. Moreover, this combined strategy does not require expensive novel technologies or high energy consumption.     

The fate of mycotoxins during thermal food processing

Mycotoxins are considered to be heat‐stable molecules. Because of their toxic effects, information about their stability in thermal processes and potential inactivation procedures is needed. Numerous reports in the literature over a number of years have described the fate of mycotoxin during thermal food processing, including cooking, boiling, baking, frying, roasting and pasteurization. This review focuses on the effects of various thermal treatments on mycotoxins, while the fate of mycotoxins during extrusion processing, which is one of the most important technologies employed in the food industry, will also be reviewed. Copyright © 2009 Society of Chemical Industry     

Influence of Water Activity on Thermal Resistance of Microorganisms in Low‐Moisture Foods: A Review

A number of recent outbreaks related to pathogens in low‐moisture foods have created urgency for studies to understand the possible causes and identify potential treatments to improve low‐moisture food safety. Thermal processing holds the potential to eliminate pathogens such as Salmonella in low‐moisture foods. Water activity (a_w) has been recognized as one of the primary factors influencing the thermal resistance of pathogens in low‐moisture foods. But most of the reported studies relate thermal resistance of pathogens to a_w of low‐moisture foods at room temperature. Water activity is a thermodynamic property that varies significantly with temperature and the direction of variation is dependent on the product component. Accurate methods to determine a_w at elevated temperatures are needed in related research activities and industrial operations. Adequate design of commercial thermal treatments to control target pathogens in low‐moisture products requires knowledge on how a_w values change in different foods at elevated temperatures. This paper presents an overview of the factors influencing the thermal resistance of pathogens in low‐moisture foods. This review focuses on understanding the influence of water activity and its variation at thermal processing temperature on thermal resistance of pathogens in different low‐moisture matrices. It also discusses the research needs to relate thermal resistance of foodborne pathogens to a_w value in those foods at elevated temperatures.     

Migration of Chemical Compounds from Packaging Polymers during Microwave,Conventional Heat Treatment,and Storage

Polymeric packaging protects food during storage and transportation, and withstands mechanical and thermal stresses from high‐temperature conventional retort or microwave‐assisted food processing treatments. Chemical compounds that are incorporated within polymeric packaging materials to improve functionality, may interact with food components during processing or storage and migrate into the food. Once these compounds reach a specified limit, food quality and safety may be jeopardized. Possible chemical migrants include plasticizers, antioxidants, thermal stabilizers, slip compounds, and monomers. Chemical migration from food packaging is affected by a number of parameters including the nature and complexity of food, the contact time and temperature of the system, the type of packaging contact layer, and the properties of the migrants. Researchers study the migration of food‐packaging compounds by exposing food or food‐simulating liquids to conventional and microwave heating and storage conditions, primarily through chromatographic or spectroscopic methods; from these data, they develop kinetic and risk assessment models. This review provides a comprehensive overview of the migration of chemical compounds into food or food simulants exposed to various heat treatments and storage conditions, as well as a discussion of regulatory issues.     

Effects of ultraviolet light and ultrasound on microbial quality and aroma-active components of milk

BACKGROUND: Heat treatment is the most common way to extend the shelf life of milk. However, alternative technologies such as ultraviolet (UV) light and ultrasound (US), which are non‐thermal methods for processing milk, have been developed to replace heat treatment. These technologies do not have any adverse effects on the quality of milk. The major purpose of this study was to investigate the effects of UV and US on different micro‐organism groups and aroma compounds in milk. RESULTS: Heat pasteurisation at 65 °C for 30 min was used as thermal control treatment. The growth of total coliform group bacteria, Escherichia coli and Staphylococcus spp. was completely reduced by UV treatment. Application of US was not sufficient to reduce the numbers of yeasts and moulds. In neutral/basic fractions, 3‐methylthiophene (plastic), hexanal (grass) and 1‐hexen‐3‐one (floral) were major volatiles in milk samples. CONCLUSION: UV had a major effect on total coliforms, E. coli and Staphylococcus spp., but US was not as effective as UV and heat treatment in reducing certain groups of micro‐organisms. No major differences were observed in terms of aroma‐active compounds and flavour of milk following the different treatments. However, some new volatiles and change in rheological properties were generated by UV and US treatments. Copyright © 2011 Society of Chemical Industry     

A Comprehensive Review on Kiwifruit Allergy: Pathogenesis,Diagnosis, Management,and Potential Modification of Allergens Through Processing

Kiwifruit is rich in bioactive components including dietary fibers, carbohydrates, natural sugars, vitamins, minerals, omega‐3 fatty acids, and antioxidants. These components are beneficial to boost the human immune system and prevent cancer and heart diseases. However, kiwifruit is emerging as one of the most common elicitors of food allergies worldwide. Kiwifruit allergy results from an abnormal immune response to kiwifruit proteins and occur after consuming this fruit. Symptoms range from the oral allergy syndrome (OAS) to the life‐threatening anaphylaxis. Thirteen different allergens have been identified in green kiwifruit and, among these allergens, Act d 1, Act d 2, Act d 8, Act d 11, and Act d 12 are defined as the “major allergens.” Act d 1 and Act d 2 are ripening‐related allergens and are found in abundance in fully ripe kiwifruit. Structures of several kiwifruit allergens may be altered under high temperatures or strong acidic conditions. This review discusses the pathogenesis, clinical features, and diagnosis of kiwifruit allergy and evaluates food processing methods including thermal, ultrasound, and chemical processing which may be used to reduce the allergenicity of kiwifruit. Management and medical treatments for kiwifruit allergy are also summarized.     

Mechanical yield regulation in winegrapes: comparison of early defoliation and crop thinning

Background and Aims: Winter pruning and manual bunch thinning are the primary methods for crop regulation in viticulture. Recently, innovative mechanical approaches have been proposed as cost‐effective for yield management. The aim of this work was to compare the effectiveness of mechanical early defoliation and mechanical crop thinning on yield regulation, and on grape and wine composition. Methods and Results: The impact of mechanical early defoliation and crop thinning, applied at different timings, was investigated in Vitis vinifera L. cv. Tempranillo vertically shoot‐positioned‐trained grapevines over two seasons. Effects on yield components, leaf area, botrytis incidence, grape and wine composition were determined. Yield per vine was drastically reduced by both techniques (35–40%). Bunch weight, number of berries per bunch, bunch compactness and botrytis were also reduced by most of the treatments. Total leaf area per vine was not affected, however, the total leaf area‐to‐yield ratio increased in most cases. Berry soluble solids, anthocyanins and total phenols increased in the grapes. Wines were higher in alcohol and more intensely coloured in mechanical early defoliation treatments in comparison with those of mechanical thinning. Conclusions: Mechanical early defoliation and crop thinning may be suitable and efficient for regulating grape yield and improving grape and wine composition. Early defoliation, however, appeared to be more consistent. Significance of the Study: Effective yield control in winegrapes may be accomplished by mechanical techniques implemented between pre‐flowering and veraison. The choice of mechanical technique for yield management may influence the grape and wine composition.     

Influence of thermal processing on IgE reactivity to lentil and chickpea proteins

In the last years, legume proteins are gaining importance as food ingredients because of their nutraceutical properties. However, legumes are also considered relevant in the development of food allergies through ingestion. Peanuts and soybeans are important food allergens in Western countries, while lentil and chickpea allergy are more relevant in the Mediterranean area. Information about the effects of thermal‐processing procedures at various temperatures and conditions is scarce; therefore, the effect of these procedures on legume allergenic properties is not defined so far. The SDS‐PAGE and IgE‐immunoblotting patterns of chickpeas and lentils were analyzed before and after boiling (up to 60 min) and autoclaving (1.2 and 2.6 atm, up to 30 min). The results indicated that some of these treatments reduce IgE binding to lentil and chickpea, the most important being harsh autoclaving. However, several extremely resistant immunoreactive proteins still remained in these legumes even after this extreme treatment.     

Effects of 1‐methylcyclopropene and post‐controlled atmosphere air storage treatments on fresh‐cut Ambrosia apple slices

BACKGROUND: The effect of 1‐methylcyclopropene (1‐MCP) treatment and two different post‐controlled atmosphere air storage (PCAAS) durations on the quality and chemistry of fresh‐cut Ambrosia apple slices was studied. RESULTS: PCAAS for 1 or 2 weeks prior to slicing had an overall positive effect on the resultant quality of fresh‐cut apple slices. The most significant responses to PCAAS were the suppression of both phenolic and o‐quinone accumulation in slices, and this was related to the significantly lower browning potential values obtained for slices from PCAAS‐treated apples. Polyphenol oxidase (PPO), peroxidase (POX) and ascorbate peroxidase (APOX) activities were not affected by 1‐MCP or PCAAS treatments. PPO and POX activities were almost completely inhibited by a 50 g L^?1 calcium ascorbate anti‐browning dip of apple slices from all treatments. CONCLUSION: The most dramatic effect of the PCAAS treatments was to reduce the accumulation of soluble phenolics, which is likely the reason that o‐quinone accumulation was also inhibited in treated fruits. The consequent reduction in browning potential may be the explanation as to why PCAAS treatment has been shown to reduce fresh apple slice browning in previous work. Copyright © 2012 Society of Chemical Industry     

Effects of processing on mycotoxin stability in cereals

The mycotoxins that generally occur in cereals and other products are not completely destroyed during food‐processing operations and can contaminate finished processed foods. The mycotoxins most usually associated with cereal grains are aflatoxins, ochratoxins, deoxynivalenol, zearalenone and fumonisins. The various food processes that may have effects on mycotoxins include cleaning, milling, brewing, cooking, baking, frying, roasting, flaking, alkaline cooking, nixtamalization, and extrusion. Most of the food processes have variable effects on mycotoxins, with those that utilize high temperatures having the greatest effects. In general, the processes reduce mycotoxin concentrations significantly, but do not eliminate them completely. This review focuses on the effects of various thermal treatments on mycotoxins. © 2014 Society of Chemical Industry     

Effect of Pectinmethylesterase Infusion Methods and Processing Techniques on Strawberry Firmness

Strawberry halves were pretreated with fungal pectinmethylesterase (PME) and calcium chloride using, respectively, passive osmotic infusion, vacuum‐assisted infusion, and pressure‐assisted infusion with the aim to improve the firmness. The vacuum‐assisted procedure was observed to be the only method able to accomplish an uptake of infusion solution and hence capable of improving the firmness of the strawberries. Significantly less firmness increase was realized when tomato PME was vacuum‐infused instead of fungal PME. Strawberry halves were pretreated by vacuum‐assisted infusion with fungal PME and calcium chloride and were subsequently subjected to thermal treatments at 60 °C and 80 °C and pressure treatments at about 400 MPa and 550 MPa. For all treatments studied, the pretreated sample was significantly firmer compared with the reference sample. For the thermal processes, the residual firmness relative to the initial value before treatment was depending on the temperature of the treatment and not on the pretreatment. However, vacuum‐assisted infusion of PME and calcium could limit the portion of firmness loss due to pressure treatment to 30% compared with 80% for non‐pretreated fruits.     

Interactions between proteins and phenolics: effects of food processing on the content and digestibility of phenolic compounds

Phenolic compounds have recently become one of the most interesting topics in different research areas, especially in food science and nutrition due to their health-promoting effects. Phenolic compounds are found together with macronutrients and micronutrients in foods and within several food systems. The coexistence of phenolics and other food components can lead to their interaction resulting in complex formation. This review article aims to cover the effects of thermal and non-thermal processing techniques on the protein–phenolic interaction especially focusing on the content and digestibility of phenolics by discussing recently published research articles. It is clear that the processing conditions and individual properties of phenolics and proteins are the most effective factors in the final content and intestinal fates of phenolic compounds. Besides, thermal and non-thermal treatments, such as high-pressure processing, pulsed electric field, cold plasma, ultrasonication, and fermentation may induce alterations  in those interactions. Still, new investigations are required for different food processing treatments by using a wide range of food products to enlighten new functional and healthier food product design, to provide the optimized processing conditions of foods for obtaining better quality, higher nutritional properties, and health benefits. © 2024 Society of Chemical Industry.     

Identification by phenotypic and genetic approaches of an indigenous Saccharomyces cerevisiae wine strain with high desiccation tolerance

During active dry yeast (ADY) production process, cells are exposed to multiple stresses, such as thermal, oxidative and hyperosmotic shock. Previously, by analysing cells in exponential growth phase, we selected an indigenous Saccharomyces cerevisiae wine strain, namely CD‐6Sc, for its higher tolerance to desiccation and higher expression of specific desiccation stress‐related genes in comparison to other yeast strains. In this study, we performed a desiccation treatment on stationary phase cells by comparing the efficacy of two different methods: a ‘laboratory dry test’ on a small scale (mild stress) and a treatment by spray‐drying (severe stress), one of the most appropriate preservation method for yeasts and other micro‐organisms. The expression of selected desiccation‐related genes has been also assessed in order to validate predictive markers for desiccation tolerance. Our data demonstrate that the ‘mild’ and the ‘severe’ desiccation treatments give similar results in terms of cell recovery, but the choice of marker genes strictly depends on the growth phase in which cells undergo desiccation. The indigenous CD‐6Sc was ultimately identified as a high dehydration stress‐tolerant indigenous strain suitable for ADY production. This study highlights the exploitation of natural yeast biodiversity as a source of hidden technological features and as an alternative approach to strain improvement by genetic modifications. Copyright © 2017 John Wiley & Sons, Ltd.     

Using lytic bacteriophages to eliminate or significantly reduce contamination of food by foodborne bacterial pathogens

Bacteriophages (also called ‘phages’) are viruses that kill bacteria. They are arguably the oldest (3 billion years old, by some estimates) and most ubiquitous (total number estimated to be 10³⁰–10³²) known organisms on Earth. Phages play a key role in maintaining microbial balance in every ecosystem where bacteria exist, and they are part of the normal microflora of all fresh, unprocessed foods. Interest in various practical applications of bacteriophages has been gaining momentum recently, with perhaps the most attention focused on using them to improve food safety. That approach, called ‘phage biocontrol’, typically includes three main types of applications: (i) using phages to treat domesticated livestock in order to reduce their intestinal colonization with, and shedding of, specific bacterial pathogens; (ii) treatments for decontaminating inanimate surfaces in food‐processing facilities and other food establishments, so that foods processed on those surfaces are not cross‐contaminated with the targeted pathogens; and (iii) post‐harvest treatments involving direct applications of phages onto the harvested foods. This mini‐review primarily focuses on the last type of intervention, which has been gaining the most momentum recently. Indeed, the results of recent studies dealing with improving food safety, and several recent regulatory approvals of various commercial phage preparations developed for post‐harvest food safety applications, strongly support the idea that lytic phages may provide a safe, environmentally‐friendly, and effective approach for significantly reducing contamination of various foods with foodborne bacterial pathogens. However, some important technical and nontechnical problems may need to be addressed before phage biocontrol protocols can become an integral part of routine food safety intervention strategies implemented by food industries in the USA. © 2013 Society of Chemical Industry     

Study of the stability of egg white protein‐based foams: effect of heating protein solution

The results reported in this study are concerned with the effects of pre‐heating treatments of ovalbumin and lysozyme solutions on the formation, stability and texture morphology of their corresponding foams. It was shown that pre‐heating solutions of these proteins to temperatures higher than that of their thermal denaturation led to an enhanced rate of surface pressure development and enhanced foaming properties relative to the unheated proteins. The effect of pre‐heating was more clearly apparent for lysozyme, which has a higher rigidity than ovalbumin in the native conformational state. Furthermore, the evolution of liquid volume retained in the lysozyme‐ and ovalbumin‐based foams and foam images during the destabilisation step indicated the slowest drainage and the finest, most homogeneous and most stable foam texture for foams formed from pre‐heated protein solutions. © 2000 Society of Chemical Industry     

Effect of thermal treatments on vitality and physical characteristics of bean,chickpea and lentil

Thermal disinfestation treatments are relatively easy to apply, leave no chemical residues and may have some fungicidal activity. However, temperature and time combinations required to kill insect pests may meet or exceed those that reduce the viability of seeds, nutrients content, shelf life or technological characteristics. The aim of this study was to investigate the effect of thermal treatments (different temperature and time combinations) on physical and biological characteristics of bean, chickpea and lentil. Seed samples of common bean, chickpea and lentil were treated at low (12, 24 or 48 h at −18 °C) or high (30, 60 or 90 min at 60 °C) temperature. Seed germination, mean germination time, physical characteristics: solids loss, electrolytes leached and firmness after cooking, were determined. The use of thermal treatments for disinfesting seeds of bean, chickpea and lentil represent a physical technique of pest control that can be harmless for seeds destined for crop production (especially for organic farming) or to be stored in germplasm banks. Moreover, thermal treatments can be applied also to grain legumes used as food by humans, with no significant effect on lentils and with a reduction of cooking time for chickpeas. Beans should be treated only with cold treatments and for no more than 24 h.     

Egg yolk: structures,functionalities and processes

Hen egg yolk is an ideal example of natural supramolecular assemblies of lipids and proteins with different organization levels. These assemblies are mainly due to interactions between proteins and phospholipids, and these interactions are essential in understanding and controlling the production of food made with yolk, and particularly emulsions. Furthermore, these assemblies can be modulated by external constraints among which thermo‐mechanical and high‐pressure treatments. This review focuses on multi‐scale structures present in egg yolk, and their modulation by processes, in relation with their emulsifying properties. Egg yolk is mainly composed of two fractions—plasma and granules—which are natural nano‐ and micro‐assemblies. These two fractions possess different composition, structures and functionalities and exhibit specific behaviour under treatments such as high pressure and temperature. Plasma contains a large quantity of lipids structured as lipoproteins (low‐density lipoproteins), whereas granules are mainly composed of proteins aggregated in micrometric assemblies. If plasma is responsible for the important emulsifying properties of yolk, granules bring interesting emulsifying properties when assemblies are in the form of micelles in presence of salts. High‐pressure or thermal treatments, applied before or after emulsion fabrication, alter their functionalities and could be used to commercially exploit these fractions. © 2013 Society of Chemical Industry     

Influence of the Thermal Stabilization Process on the Volatile Profile of Canned Tomato‐Based Food

The literature contains several papers dealing with the volatile constituents contributing to the aroma of fresh and processed tomatoes. Along with the traditional tomato‐based products, tomato‐based pâtés, characterized by complex ingredient formulations, are commonly consumed as a seasoning for pasta, and as a dressing for meats, salads, and sandwiches. To the best of our knowledge, no investigations have been published on the influence of thermal stabilization treatments on the composition of volatile compounds in tomato‐based pâtés. To this aim, thermally stabilized and not stabilized tomato‐based pâtés were subjected to the analysis of volatile compounds. The results obtained highlighted the influence of the thermal stabilization process on the evolution of volatile composition tomato‐based pâtés. In particular, the terpenic compounds showed significant decreases after the thermal stabilization process treatment, due to their degradation and oxidation favored by high temperatures. The thermal stabilization caused, moreover, an increase in volatile compounds deriving from lipid oxidation and Maillard reaction, characterized by low‐sensory thresholds, and from the thermal degradation of carotenoids and fresh tomato‐derived compounds.     

Application of thermal treatments to enhance gel strength and stability of highly concentrated crayfish-based emulsions

Highly concentrated oil-in-water (O/W; 25:75 wt%) emulsions stabilized by crayfish flour (CF) have been subjected to thermal treatments in order to study potential enhancements on gel strength of the network structures formed among oil droplets, involving adsorbed and non-adsorbed protein segments. Application of in situ thermal treatments, monitored by Small Amplitude Oscillatory Shear (SAOS), may lead to remarkable changes in the gel strength of CF-based emulsions, depending on processing conditions. If the heating temperature is above a critical value, the exposition time being long enough, thermal energy eventually leads to coalescence of oil droplets and subsequent emulsion destabilization. This behaviour has been confirmed by Droplet Size Distribution (DSD) measurements. The pH exerts a strong influence on the evolution of viscoelastic moduli. Little changes are produced at alkaline conditions, whereas a noticeable enhancement is apparent at neutral and acid pH. Application of consecutive double thermal cycle confirms the reversibility of the reinforcement induced by the cooling stage. The results may be explained in terms of the balance between electrostatic forces (predominant at alkaline pH) and hydrophobic interactions that favour protein aggregation and crosslinking (over heating stages), as well as hydrogen bonding (at the cooling stage).In addition, the influence of gel strength enhancement on the subsequent improvement of emulsion stability has been investigated by applying thermal treatments in a thermostatic bath. A clear enhancement in emulsion stability is achieved by these thermal treatments, although its contribution is not enough to produce long-term stability and a combination with other stabilizing strategies should be developed.     

Alternatives to conventional thermal treatments in fruit-juice processing. Part 2: Effect on composition,phytochemical content,and physicochemical,rheological, and organoleptic properties of fruit juices

Traditional thermal techniques may cause losses in nutritional quality and phytochemical contents, and also in physicochemical, rheological, and organoleptic properties of processed fruit juices. This paper provides an overview of the effect on these qualities by the use of alternatives to traditional thermal treatments in fruit-juice processing, for three key operations in fruit-juice production such as microbial inactivation, enzyme inactivation, and juice-yield improvement. These alternatives are UV light, high-intensity light pulses, γ-irradiation, pulsed electric fields, radiofrequency electric fields, Ohmic heating, microwave heating, ultrasound, high hydrostatic pressure, supercritical carbon dioxide, ozonation, and flash-vacuum expansion. Although alternatives to heat treatments seem to be less detrimental than the thermal treatment, there are many parameters and conditions that influence the output, as well as the nature of the juice itself, hampering comparisons between different studies. Additionally, future research should focus on understanding the mechanisms underlying the changes in the overall quality of fruit juices, and also on scaled-up processes, process design, and optimization that need to be deal with in detail to maximize their potential as alternative nonthermal technologies in fruit-juice processing while maintaining fruit-juice attributes to the maximum.