Intense Heat Treatment Research Articles

Long-Term Casein-Bound Lactulosyllysine Consumption Induced Nonobese Nonalcoholic Fatty Liver Disease by Promoting Carbonyl Glycation in the Liver of C57BL/6 Mice.

Lactulosyllysine (LL) is abundant in thermally processed dairy products, with its concentration increasing in response to more intense heat treatment. However, there are limited studies on the potential harmful effects of LL on human health. This study investigated the negative impact of casein-bound LL on liver health by feeding healthy C57BL/6 mice diets containing varying levels of casein-bound LL. After 16 weeks of LL diet administration, mice exhibited a nonobese nonalcoholic fatty liver disease (NONAFLD) phenotype, characterized by reduced body weight gain, hypolipidemia, and intrahepatic lipid accumulation. Nontarget metabolomic analysis showed that casein-bound LL induced alterations in plasma levels of compounds associated with lipid degradation. Mechanistically, casein-bound LL may impair the function of 5'-adenosine monophosphate-activated protein kinase and apolipoprotein B100 by inducing dicarbonyl stress, thereby promoting carbonyl glycation in the liver. Consequently, the long-term consumption of LL-rich dairy products may be a contributing factor to the risk of developing NONAFLD.

Intense pulsed light-induced millisecond selective heat treatment for high-performance silicon anodes

Silicon, which is gaining prominence as a potential anode material, exhibits long-term cycle stability issues owing to volume changes during cycling. This study presents a meticulously designed Si anode that employs intense pulsed light (IPL) technology to simultaneously reduce carbon additives and construct an effective carbon quantum dot (CQD)-derived binder system. IPL, as a light-material interaction technique, offers a novel approach for selective heat treatment with remarkably short processing durations on the order of milliseconds. By comprehensively considering the geometric structure, optical characteristics, and thermal properties of each electrode component, heat transfer bridge (HTB) materials are introduced to ensure a homogeneous depth-directional heat treatment and to minimize binder decomposition in the IPL process. By employing HTB materials, the binder can reach a controlled target temperature for the condensation reaction between poly (acrylic acid) and the CQDs. Simultaneously, higher heat generation in the conductive carbon than in the binder leads to selective additional carbon reduction. This unique approach provides selective heat treatment, which cannot be achieved using conventional methods, resulting in a Si anode with excellent cyclic stability and rate capability. The versatility of the IPL technology is further demonstrated by applying it to relatively inexpensive Si microparticles.

Changes in nutritional and technological properties of heat-treated milk and cream at dairy production scale during storage

Changes in nutritional and technological properties during storage of milk and cream subjected to different heat treatments at dairy production scale (high-temperature-short-time pasteurisation, extended shelf-life treatment and ultra-high temperature treatment) were investigated. Results indicate a decrease in pH with longer storage times, whereas no changes in ionic calcium concentration occurred during shorter storage. Vitamin losses ranged from 1 to 22% for different heat treatments and more pronounced effects of vitamin degradation was observed with more intense heat treatment and longer storage times. Vitamin B12 concentration tended to decrease more over time than vitamins B1, B2 and E and more losses in vitamin concentration were found after storage than after heat treatment. Significant effects on physical stability and colour changes in milk and cream were observed during prolonged storage. This suggests that larger changes in nutritional and technological quality of heat-treated milk and cream at dairy production scale occur during longer storage times.

Comparative lipidomics analysis of in vitro lipid digestion of sheep milk: Influence of homogenization and heat treatment

This study investigated the changes in sheep milk lipids during in vitro gastrointestinal digestion in response to heat treatment (75°C/15 s and 95°C/5 min) and homogenization (200/50 bar) using lipidomics. Homogenized and pasteurized sheep milk had higher levels of polar lipids in gastric digesta emptied at 20 min than raw sheep milk. Intense heat treatment of homogenized sheep milk resulted in a reduced level of polar lipids compared with homogenized-pasteurized sheep milk. The release rate of free fatty acids during small intestinal digestion for gastric digesta emptied at 20 min followed the order: raw ≤ pasteurized < homogenized-pasteurized ≤ homogenized-heated sheep milk; the rate for gastric digesta emptied at 180 min showed a reverse order. No differences in the lipolysis degree were observed among differently processed sheep milks. These results indicated that processing treatments affect the lipid composition of digesta and the lipolysis rate but not the lipolysis degree during small intestinal digestion.

Acid and rennet gelation properties of sheep, goat, and cow milks: Effects of processing and seasonal variation

Gelation is an important functional property of milk that enables the manufacture of various dairy products. This study investigated the acid (with glucono-δ-lactone) and rennet gelation properties of differently processed sheep, goat, and cow milks using small-amplitude oscillatory rheological tests. The impacts of ruminant species, milk processing (homogenization and heat treatments), seasonality, and their interactions were studied. Acid gelation properties were improved (higher gelation pH, shorter gelation time, and higher storage modulus (G') by intense heat treatment (95°C for 5 min) to comparable extents for sheep and cow milks, both better than those for goat milk. Goat milk produced weak acid gels with low G' (<100 Pa) despite improvements induced by heat treatments. Seasonality had a marked impact on the acid gelation properties of sheep milk. The acid gels of late-season sheep milk had a lower gelation pH, no maximum in tan δ following gel formation, and 70% lower G' values than those from other seasons. We propose the potential key role of a critical acid gelation pH that induces structural rearrangements in determining the viscoelastic properties of the final gels. For rennet-induced gelation, compared with cow milk, the processing treatments of the goat and sheep milks had much smaller impacts on their gelation properties. Intense heat treatment (95°C for 5 min) prolonged the rennet gelation time of homogenized cow milk by 8.6 min (74% increase) and reduced the G' of the rennet gels by 81 Pa (85% decrease). For sheep and goat milks, the same treatment altered the rennet gelation time by only less than 3 min and the G' of the rennet gels by less than 14 Pa. This difference may have been caused by the different physicochemical properties of the milks, such as differences in their colloidal stability, proportion of serum-phase caseins, and ionic calcium concentration. The seasonal variations in the gelation properties (both acid and rennet induced) of goat milk could be explained by the minor variation in its protein and fat contents. This study provides new perspectives and understandings of milk gelation by demonstrating the interactive effects among ruminant species, processing, and seasonality.

Use of molecular networking to identify 2,5-diketopiperazines in chocolates as potential markers of bean variety

2,5-diketopiperazines are cyclic dipeptides found, among others, in chocolate. Although those compounds are contributing greatly to its pleasant bitterness, they can also be seen as interesting markers of cocoa beans processing. To evaluate the influence of bean variety and processing technology on the quantity of 2,5-diketopiperazines formed in chocolates, HPLC-MS/MS analyses were conducted, and a molecular network was built with the MS2 data. This approach eases the identification of 2,5-diketopiperazines within complex datasets and allows to visualize the chemical diversity of all samples. Using this methodology, 33 dark chocolates were analysed. 18 different diketopiperazine were identified and quantified. Among them, cyclo(L-ile-L-val), cyclo(L-leu-L-ile) and cyclo(L-phe-L-phe) were, to the best of our knowledge, detected for the first time in chocolate. The molecular network allows the clear visualization of differences between samples. The principal component analysis revealed the clustering of small batch chocolate samples according to bean variety, suggesting that bean genotype has a strong influence on the 2,5-diketopiperazines content of bean-to-bar chocolates, regardless of the degree of roasting or the technological process used by the small producers. The presence of two unique diastereoisomers in the classical chocolates bought in the supermarket indicates that the beans have probably undergone a more intense heat treatment. This study proposes the use of 2,5-diketopiperazines as potential markers of cocoa beans variety, as well as an indicator of post-harvest processing and processing technology, and highlights the potential of the molecular networks in the field of food and drink innovation as a promising tool to understand the complex chemistry of flavours.

Anaerobic Bacterial Biofilms Inhibit Neutrophil Responses via the Release of Stable Small‐Molecule Effectors

Background and ObjectiveFusobacterium and Porphyromonasare two genera of opportunistic pathogens that often aggregate in complex communities known as biofilms. Host innate immune cells are frequently frustrated when they encounter biofilm bacteria, resulting in ineffectual clearance and persistent infection. Anaerobic pathogens generate or accumulate organic molecules and use them as defense against environmental pressures such as oxidative stress or attack from host immune cells. Porphyromonasspecies utilize protoporphyrin IX (PPIX) to protect against neutrophil oxidative‐killing. The objective was to develop a model of mixed‐species biofilm generation and to evaluate bovine neutrophil responses to bioactive molecules released from either biofilm or planktonic bacteria. We hypothesized that biofilm‐conditioned growth medium would contain more PPIX than planktonic medium and therefore inhibit the functional responses of peripheral neutrophils.MethodsNeutrophils were isolated from whole blood via hypotonic lysis and bacterial biofilms were generated using previously validated methods for the cultivation of mixed‐species biofilms. Spent media from biofilm and overnight planktonic cultures were collected, centrifuged, and filtered to remove viable bacteria. Supernatants were fractionated via &lt;3kDa‐cutoff filtration and exposed directly to neutrophils. Neutrophil responses to the supernatants were assessed with a fluorescent microplate assay for reactive oxygen species (ROS) and chemotaxis was measured with a Transwell® transmigration assay. The specific mechanism of neutrophil activation was investigated by employing NF‐κB and NADPH oxidase inhibitors.ResultsNeutrophils exposed to planktonic supernatant showed significantly elevated oxidative and chemotactic responses compared to biofilm products from identical bacteria. Ultra‐filtration revealed that a &lt;3kDa molecule is differentially expressed in the supernatants and allows biofilm‐bacteria to inhibit neutrophil responses. Intensive heat, nuclease, lipase, and protease treatment of the &lt;3kDa fractions did not alter neutrophil functional responses. Preliminary experiments suggest that the accumulation of PPIX in the biofilm supernatant attenuates neutrophil chemotaxis and ROS production. In addition, chemical inhibition experiments indicated that neutrophils respond to planktonic supernatants independently of NF‐κB signaling.ConclusionsExperiments reveal a minimal neutrophil response to molecules released from biofilm bacteria and may explain the inadequate host response to biofilm‐mediated infections. The phenotypic changes in the biofilm mode of growth allow for the generation and accumulation of PPIX, providing protection from host immune clearance mechanisms. Understanding the mechanism of immune avoidance is a crucial step to reduce the persistent inflammation and negative clinical outcomes associated with chronic biofilm‐mediated disease.

Two-Step Continuous Cooling Heat Treatment Applied in a Low Carbon Bainitic Steel

Thermo-mechanical treatments using continuous cooling after forging are an established method for producing bainitic steels, mainly because of the elimination of energy intensive additional heat treatment processes. The cooling is usually employed in an uncontrolled manner in the industrial sector, which can be detrimental to the resulting microstructural morphology and, consequently, to the final product properties. In this study, a new controlled two-step cooling route based on the principles of bainitic displacive growth was designed and applied in a 0.18C (wt-%) steel. Inverse finite element method was used on the cooling data to obtain the evolution of temperatures for the samples during cooling, allowing to assess point to point cooling rates. Investigations via X-ray diffraction, optical microscopy analysis and hardness testing revealed a variation of bainitic morphology, namely, the transition from granular bainite to lath-like bainite with relatively high hardness and constituents/phase boundaries than the pre-treated microstructure.

Encapsulation of grape seed phenolics from winemaking byproducts in hydrogel microbeads – Impact of food matrix and processing on the inhibitory activity towards α-glucosidase

Hydrogel-based encapsulation systems were developed for grape seed phenolics recovered from winemaking byproducts. Proanthocyanidins, monomeric flavanols, flavonols and anthocyanins were extracted from grape seeds with 60% ethanol. Encapsulation of solubilized grape seed phenolics in microbeads with alginate-Ca++ or alginate-chitosan-Ca++ achieved efficiency of 78 and 92%, respectively, higher than those of pure catechin and proanthocyanidins.Encapsulated phenolics showed inhibitory activity towards the brush border enzyme α-glucosidase, which was chosen as a model bioactivity assay. Grape seed phenolics were retained in the hydrogel structure after mixing of the microbeads with bovine milk or rice drink, pasteurization of these beverages to achieve 7 decimal reductions of Mycobacterium avium subsp. paratubercolosis (equivalent to 72 °C for 91 s) as well as after intense heat treatment of the rice beverage to achieve 7 decimal reductions of Bacillus cereus (95 °C for 20 min).

Biofilm and Planktonic Bacteria Differentially Express a Small Molecule (&lt;3kD), Heat‐Stable, Protease‐Resistant Factor that Affects Bovine Neutrophil Function in a NF‐Kappa β‐Independent Mechanism

IntroductionChronic bacterial infections and the associated inflammation have a significant impact in both veterinary and human medicine. Bacterial biofilms are a major cause of the persistent inflammation observed in chronic infections and nearly 80% of all infections involve biofilms. Biofilms are typically polymicrobial in composition and many of these mixed‐infections involve anaerobic bacteria. Recent evidence demonstrates that immune cells often disregard the signals released from biofilm bacteria, and ineffectual clearance of biofilms may explain the chronicity of this sort of infection. A mixed‐species model of anaerobic biofilm growth was developed to evaluate medically relevant biofilms and their interactions with bovine neutrophils.AimsTo generate mixed‐species bacterial biofilms composed of the two opportunistic pathogens Fusobacterium necrophorum and Porphyromonas levii, and to employ the in vitro system to investigate factors associated with biofilms that may limit neutrophil functional ability.MethodsMixed‐species biofilm formation was verified with SEM, CLSM and viable cell counts. Neutrophil oxidative burst was assessed with a fluorescent microplate assay for hydrogen peroxide. Chemotaxis was measured with a Transwell transmigration assay. Extracellular factors released from planktonic cultures and biofilms were assessed by size‐exclusion filtration, lipopolysaccharide (LPS) removal, protease and heat treatment. Mechanistic experiments to study neutrophil responses to these supernatants were conducted with specific inhibitors of function, such as NF‐κβ signaling (BAY‐11) and inflammasome activation (glyburide).ResultsNeutrophils exposed to planktonic bacterial supernatants showed significantly elevated oxidative (4‐fold increase in fluorescence) and chemotactic responses compared to neutrophils exposed to biofilm products from identical bacteria. LPS plays a significant role in the stimulation of neutrophils; in this experiment biofilms produced substantially more LPS than planktonic bacteria despite inducing less neutrophil response. Removal of LPS resulted in similar neutrophil responses to planktonic and biofilm supernatants.Size‐exclusion filtration of bacterial supernatants and subsequent exposure to neutrophils revealed that the active stimulatory molecule is below 3 kD and is released strictly from planktonic cultures. Intensive heat and protease treatment of the &lt;3kD fractions did not alter neutrophil functional responses. Treatment with a NF‐κβ inhibitor demonstrated that neutrophils respond specifically to planktonic supernatants independently of NF‐κβ signaling.ConclusionsWe describe a heat‐stable, protease‐resistant, non‐LPS, small (&lt;3kD) factor produced by in vitro planktonic cultures of F. necrophorum and P. levii that activates bovine neutrophils. Neutrophils did not exhibit the same oxidative and chemotactic responses upon exposure to in vitro generated biofilm supernatants and these differential responses are the result of a NF‐κβ independent mechanism, perhaps through an inflammasome‐mediated process.Support or Funding InformationFunding provided by the University of Calgary Grant 10002461 to DW Morck.

Efficient use of microwave EMF and multilevel high temperature sterilization modes in apple puree technology for dietetic nutrition

The article is dedicated to improving the quality of apple puree with xylitol for dietetic nutrition due to the development and implementation of a new technological process. This is microwave boiling of apples, rather than traditional steaming using saturated steam before chopping, with the development of a device for its implementation and multilevel high-temperature sterilization modes with prebake of apple puree in glass jars in microwave EMF. The analysis of research and technical data proved that pre-heat treatment of apples with saturated steam and traditional sterilization modes have a considerable duration, which impairs the finished products quality and has an adverse effect on the nutrient composition of the raw material during processing. Substituting the traditional method of pre-heat treatment of apples for their short-time processing in microwave EMF reduces the process by more than twice, which, in turn, contributes to an increased preservation of the nutrient composition of apples, while enhancing the yield of apple puree. For the implementation of microwave processing method of raw materials, a new design of the device for electromagnetic treatment of plant roughage has been developed, providing a uniform and more intensive heat treatment of raw materials in a continuous flow. Rapid multilevel high-temperature sterilization modes with the application of apple puree in glass jars in microwave EMF, liquid high-temperature heat devices and an autoclave basket, providing the opportunity for thermal sterilization of the product without creating reverse pressure in the machine, generally contribute to reducing heat costs and increasing the nutritional value.

Effect of UV light on food quality and safety

Abstract The recent years have seen a great number of instances when ultraviolet (UV) radiation was used in the preservation process of all sorts of foods. Since the purine and pyrimidine bases of DNA and RNA absorb well the 254 nm radiation, its application with the use of a correct dosage can result in disinfections of various orders of magnitude. It can be particularly effective in cases where technology does not allow a more intensive heat treatment. When used properly, UV treatment can be a competitive procedure in the case of foodstuffs where the large surface area allows for UV rays to penetrate the entire volume of the substance. Incorrectly applied UV treatment may change the composition of foods. Free-radical as well as photochemical reactions can digest the proteins, damage the antioxidants, oxidize the lipids, make changes to the colour and substance, and produce undesirable flavourings and odorous substances. Some vitamins are particularly sensitive to UV irradiation in the course of which losses could reach even 50%. Photosensitive water-soluble vitamins are vitamin C, B12, B6, B2 and folic acid, while vitamins A, K and E are the fat soluble sensitive to light, carotene being the only provitamin with such properties. On the other hand, UV treatment can be a useful tool of food safety because of the photosensitivity of fungal toxins.

Woman and child: The singular testimony of a Punic tomb in the necropolis of Monte Sirai (Carbonia-Sardinia, Italy)

In this paper we present a case of a double burial (T.310/326) from the Phoenician Punic necropolis of Monte Sirai (Carbonia, Sardinia, Italy). This peculiar tomb, which comprises the inhumation of a woman, presents unique constructive features, namely a big stone cover that confers a high visual reference to the necropolis. Furthermore, a cooking pot with two handles was laid on the tibias during the final closure of the tomb which included remains from at least three birds of the Turdidae family. Strikingly, these remains were mixed with those from a perinatal infant who could possibly constitute the progeny of the woman buried in the tomb. The combined XRD/FT-IR analysis showed that the infant remains underwent intense heat treatment, while the adult and bird remains remained unburned. This urned infant burial involving perinatal and animal remains has close analogies with practices of infant depositions in the contemporaneous Phoenician and Punic tophet sanctuaries of the central Mediterranean.

Liberation and Micellarization of Carotenoids from Different Smoothies after Thermal and Ultrasound Treatments.

The consumption of a varied diet rich in fruit and vegetables helps prevent and treat certain chronic diseases. The development of smoothies based on derivatives from fruit and vegetables rich in bioactive compounds can help increase the consumption of these foods, and therefore, contribute to the prevention of various health problems. However, during the processing of the fruit and vegetable smoothies, these properties may change. The elaboration of smoothies is based on fruits and vegetables rich in carotenoids: Carrot juice-papaya-mango (smoothie A) and carrot juice-pumpkin-mango (smoothie B). The objective of this study is to evaluate the impact of the application of different thermal technologies (mild and intensive heat treatment) and non-conventional technologies (ultrasound) on carotenoids (α-carotene, β-carotene, lutein and β-cryptoxantin) and determine the physiochemical parameters of derivatives from fruit and vegetable smoothies. In addition, the bioaccessibility of carotenoids is also evaluated through a process of in vitro simulated digestion. With regard to the bioaccessibility of the fruit and vegetable smoothies analyzed, a positive effect of temperature on liberation and micellarization was observed.

Microstructural evolution of white and brown etching layers in pearlitic rail steels

The formation of White (WEL) and Brown Etching Layers (BEL) on rail raceways during service causes the initiation of microcracks which finally leads to failure. Detailed characterization of the WEL and the BEL in a pearlitic rail steel is carried out from micrometer to atomic scale to understand their microstructural evolution. A microstructural gradient is observed along the rail depth including martensite, austenite and partially dissolved parent cementite in the WEL and tempered martensite, ultrafine/nanocrystalline martensite/austenite, carbon saturated ferrite and partially dissolved parent cementite in the BEL. Plastic deformation in combination with a temperature rise during wheel-rail contact was found to be responsible for the initial formation and further microstructural evolution of these layers. The presence of austenite in the WEL/BEL proves experimentally that temperatures rise into the austenite range during wheel-rail contact. This is in agreement with finite element modelling results. Each wheel-rail contact must be considered as an individual short but intense deformation and heat treatment cycle that cumulatively forms the final microstructure, as shown by diffusion length calculations of C and Mn. The presence of secondary carbides in the BEL indicates that the temperature in the BEL during individual loading cycles reaches levels where martensite tempering occurs. Partially fragmented primary cementite laths, enriched in Mn, depleted in Si, and surrounded by a C-gradient and dislocations were found in the BEL. The initial step in the formation of BEL and WEL is the defect- and diffusion-assisted decomposition of the original microstructure.

HUMAN EXPOSURE TO BIOLOGICALLY ACTIVE HETEROCYCLIC AROMATIC AMINES ARISING FROM THERMAL PROCESSING OF PROTEIN RICH FOOD

Frequent consumption of thermally processed meat was classified by the International Agency for Research on Cancer to directly carcinogenic agents for humans. During the heat treatment of high protein food, mutagenic and carcinogenic, as well as neurotoxic heterocyclic aromatic amines are formed. Epidemiological studies confirm that exposure to some of these compounds may increase the risk of cancer in humans, especially the colon cancer. Most heterocyclic amines contain fried and grilled meat products, and the lowest content of these compounds can be found in boiled and slightly baked dishes. The use of spices and vegetable additives with antioxidant properties allows to obtain dishes with reduced content of these xenobiotics. An effective way to reduce human exposure to cancerogenic amines may be simultaneous consumption, together with meat dishes, products containing fiber which can adsorb molecules of heterocyclic amines in the gastrointestinal tract, as well as enrichment of the diet in the crucifers plants, as isothiocyanates released from them can inhibit the metabolic activation processes of heterocyclic amines. Raising the public awareness of the formation of mutagenic and carcinogenic compounds, including heterocyclic aromatic amines, during the intensive heat treatment of high protein food, as well as the dissemination of knowledge on the conditions regarding the preparation of dishes with reduced content of such compounds could become one of the components of cancer prevention programs in Poland.

Antioxidant capacity of Maillard reaction products in the digestive tract: An in vitro and in vivo study.

The release of biscuit Maillard reaction products (MRP) with antioxidant capacity was compared by in vitro and in vivo studies. Antioxidant determinations were performed by DPPH, FRAP and ICRED. Results indicated that an intense heat treatment on biscuits increases the amount of MRP with antioxidant capacity (p < 0.05). Besides, a low amount of antioxidant compounds was obtained after enzymatic digestion, whereas the highest proportion was released by colonic bacteria. Moreover, a high amount of non-released antioxidant compounds remained in faeces of Wistar rats; this was only predicted by in vitro ICRED determination. In addition, an increase in the stool amount and in the cecum weight/body weight ratio was observed in animals fed with a diet enriched in MRP (p < 0.05), which indicated a possible prebiotic activity. In conclusion, the in vitro digestion/fermentation procedure combined with ICRED determination would be a useful methodology to predict the release of antioxidant MRP in vivo.

Inter- and intra-species variability in heat resistance and the effect of heat treatment intensity on subsequent growth of Byssochlamys fulva and Byssochlamys nivea

The major aims of this study were to assess inter- and intra-species variability of heat resistant moulds (HRMs), Byssochlamys fulva and Byssochlamys nivea, with regards to (i) heat resistance and (ii) effect of heat treatment intensity on subsequent outgrowth. Four-week-old ascospores were suspended in buffered glucose solution (13° Brix, pH 3.5) and heat treated in a thermal cycler adjusted at 85 °C, 90 °C and 93 °C. Two variants of the Weibull model were fitted to the survival data and the following inactivation parameters estimated: b (inactivation rate, min−1), n (curve shape) and δ (the time taken for first decimal reduction, min). In addition to the assessment of heat resistance, outgrowth of Byssochlamys sp. from ascospores heated at 70 °C, 75 °C, 80 °C, 85 °C and 90 °C for 10 min and at 93 °C for 30 and 70 s was determined at 22 °C for up to 30 days. The Baranyi and Roberts model was fitted to the growth data to estimate the radial growth rates (μmax, mm.day−1) and lag times (λ, days). Inter-species variability and significant differences (p < 0.05) were observed for both inactivation and growth estimated parameters among B. fulva and B. nivea strains. The effect of heat treatment intensity on outgrowth of B. fulva strains was more apparent at the most intense heat treatment evaluated (90 °C/10 min), which was also the condition in which greater dispersion of the estimated kinetic parameters was observed. On the other hand, B. nivea strains were more affected by heating, resulting in greater variability of growth parameters estimated at different heating intensities and in very long lag phases (up to 25 days). The results show that inter- and intra-species variability in the kinetic parameters of Byssochlamys sp. needs to be taken into account for more accurate spoilage prediction. Furthermore, the effect of thermal treatments on subsequent outgrowth from ascospores should be explored in combination with other relevant factors such as °Brix and oxygen to develop thermal processes and storage conditions which can prevent the growth of HRMs and spoilage of heat treated food products.

Effect of heat treatment intensity on the survival, activation and subsequent outgrowth of Byssochlamys nivea ascospores

The objective of this study was to evaluate the combined effects of heat treatment intensity and pH on the activation/inactivation of ascospores of Byssochlamys nivea and their subsequent outgrowth. D-values were evaluated at 85, 90 and 95 °C, whilst activation/inactivation and outgrowth were determined by a full factorial study incorporating (i) heat treatments ranging from no heat treatment to 10 min at 55–90 °C and (ii) pH values ranging from 4 to 6. The estimated D-values were independent of pH and ranged from 1.1 to 1.2 min at 90 °C to 15–16 min at 85 °C. Optimal heat activation was observed when the ascospores were heated for 10 min at 75 °C. Whilst heat activation (10 min at 65–75 °C) did not have a significant effect (p > 0.05) on the lag phase of B. nivea relative to native ascospores, significantly (p < 0.05) longer lag phases were observed when heat treatments of 10 min at ≥85 °C were applied. The longest lag phases were observed when the most intense heat treatment evaluated in the study was applied. The results show that reduction of heat treatment intensity could have an impact on the shelf-stability of foods which are contaminated by ascospores of heat resistant moulds.

Influence of intensive vacuum mixing and heat treatment on compressive strength and microstructure of reactive powder concrete incorporating secondary copper slag as supplementary cementitious material

In this study the effect of vacuum mixing and heat treatment on the compressive strength and microstructure of reactive powder concrete (RPC), made with secondary copper slag as partial cement replacement is investigated. The quickly cooled granulated copper slag was ground using a planetary ball mill. A low water-to-binder ratio of 0.185 was chosen. The series of concrete mixtures and cement paste samples were produced with copper slag contents from 0 to 20wt%. The pozzolanic activity of slag was determined by the Frattini test. The performance of RPC mixed under vacuum conditions and heat-cured was compared to that of RPC mixed at atmospheric pressure without heat treatment. The porosity evolution of RPC was investigated by mercury intrusion porosimetry.A higher workability of the fresh RPC was obtained by mixing under atmospheric pressure. The presence of copper slag in the RPC had no adverse effect on compressive strength for all treatments. The heat treatment decreases the porosity and enhances the RPC strength. Assessment of the pozzolanic activity by means of the Frattini test indicates low pozzolanic reaction of the slag after 15days. The presence of slag in the paste tends to decrease the total heat production of the paste. The use of copper slag as cement replacement in the RPC production decreases the energy consumption and reduces the carbon footprint.