Intense Heat Treatment Research Articles

Mathematical Model of Interaction Between Bacteriocin-Producing Lactic Acid Bacteria and Listeria. Part 2: Bifurcations and Applications.

The big challenge for the food industry is the attending to demands for minimally processed foods, avoiding intense heat treatments and reducing the addition of chemical preservatives, but at the same time ensuring microbiological safety of these products. Lactic acid bacteria are traditionally used in the production of fermented foods. They are responsible for the production of antimicrobial compounds, such as organic acids and bacteriocins, which are protein compounds with bactericidal effect against related species and bacteria such as Listeria monocytogenes and Staphylococcus aureus. Aiming to study quantitatively the biological control as a technique of conservation, we developed a mathematical model to describe the interaction between lactic acid bacteria and Listeria in the food. The steady state and dynamical trajectories analyses of the model permit us to study the suitability of including lactic acid bacteria in order to reduce the growth of Listeria in food.

Экспериментальное изучение плотности распределения частиц материала в шнековой установке

The experimental studies of density distribution of the particles of a mixture of wheat, oats, rye to feed pigs by infrared heating at the time of stay and temperature at the exit of the installation. The purpose of the work is to study the quality of treatment of the product with the settings with the screw and the screw with installed round jumper on the pen of the screw. Screw installations with infrared emitters of selected wavelength give the opportunity for intense and continuous heat treatment process. The authors used the optimal parameters of the process with the screw and the screw with installed round jumper on the pen of the screw. The parameters of screw installation during the study were the following: the number of revolutions of the screw was 10 rpm, density of heat flux was 12 kW/m2, output capacity – 250 kg/h.

Influence of dairy matrices on nutrient release in a simulated gastrointestinal environment

The objective of this study was to compare the kinetics of the release of nutrients (peptides and fatty acids) from different dairy matrices (milks, yogurts, and cheeses) in a simulated gastrointestinal environment. Prior to processing, different heat and homogenization treatments were applied to milks, and different drainage pH levels were used to control calcium concentration in cheeses. The dairy matrices were then subjected to simulated digestion. Matrix degradation, protein hydrolysis, and fat hydrolysis were analyzed during the gastric and intestinal digestion phases. Intense heat treatment of milk induced faster digestion of proteins in the gastric environment. Cheeses were more resistant to protein and lipid digestion than liquid or semi-solid matrices were. No direct relationship could be established between disintegration kinetics and cheese rheological properties. Fatty acid release in the intestinal phase was much faster when matrices were produced from homogenized milk. For cheeses, greater fatty acid release could not be related to faster matrix disintegration, suggesting that the lipid droplet size dispersion was more important than matrix breakdown was for the modulation of lipid digestion kinetics. Calcium soaps were produced in the intestinal environment, and their concentration was higher during the digestion of cheeses in comparison with milks and yogurts. These results suggest that processing-induced modifications to the composition, microstructure, and rheological properties of dairy matrices could be used to control nutrient delivery.

A Novel Rapid Processing Route to Sintered Plaque Aqueous Nickel Electrodes for Low Cost Building Scale Energy Storage

Electrification of heating systems and transportation as well as decarbonisation of electrical energy production will continue to place more and more stress and strain on current electrical grid infrastructures. Renewable energy generation technologies such as photovoltaics and wind power generation are seen by many as the future for energy production and security. With high dependence on such intermittent and ‘highly distributed micro-generation’ energy production technologies, ‘highly distributed micro-storage’ solutions such as secondary batteries could prove to be the answer. An appropriate technology would ideally possess a lifetime in-line with current photovoltaic technologies (20 years), be inherently safe and be able to cope with the unpredictable cycling conditions posed by intermittent generation and user demand. One such technology, namely nickel-iron aqueous batteries (pioneered by Thomas Alva Edison in 1901) boasts cycle life in excess of 5000 cycles, as well as tolerance of both physical and electrical abuse. Low energy density (both gravimetrically and volumetrically) are long standing issues with the chemistry, however given the nature of the application, such issues are not of the greatest concern. The greatest issue posed by the nickel cathode material is the poor high rate charge/discharge capability, due to the insulating nature of nickel hydroxide active materials. This can be addressed by configuring the cathode active material within a conductive scaffold (sintered nickel plaque on nickel-plated steel current collector). This does however hinder manufacturability of the cathode, requiring a highly energy intensive heat treatment (900oC, 30 minutes). Herein we evaluate electrodes produced via 2 process routes: - A traditional process route consisting of a slurry deposition and subsequent convection sintering process and a continuous current active material deposition process, versus a novel rapid process route, utilising high volume throughput screen printing of both nickel and titanium dioxide scaffolds and Near Infrared rapid curing technology, as well as a pulsed current active material deposition. The latter results in a substantial reduction in manufacture time, opening the door to semi-continuous processing for sintered nickel battery technologies and therefore low-cost energy storage.

Influence of lupin-based milk alternative heat treatment and exopolysaccharide-producing lactic acid bacteria on the physical characteristics of lupin-based yogurt alternatives

In the present study we investigated the influence of heat treatment of lupin-based (LB) milk alternatives and different exopolysaccharide (EPS)-producing lactic acid bacteria on the physical characteristics of set-type LB yogurt alternatives. LB milk alternatives, obtained from protein isolate of Lupinus angustifolius cv. Boregine, were either pasteurized at 80°C for 60s or ultra-high temperature (UHT) heated at 140°C for 10s and was fermented with Lactobacillus plantarum TMW 1.460 and 1.1468, Pediococcus pentosaceus BGT B34 and Lactobacillus brevis BGT L150. Fermentation duration was strongly affected by heat treatment: different strains needed between 25 to 35h in UHT LB milk alternative to reach a pH of 4.5 compared to 14 to 24h in pasteurized LB milk alternative. EPS extraction revealed slightly higher amounts of EPS for UHT LB yogurt alternatives (~0.5–0.9g/l; pasteurized: ~0.4–0.7g/l). The more intensive heat treatment (UHT) resulted also in better rheological (apparent viscosity, hysteresis loop area, flow point, elastic, viscous and complex modulus) and textural properties (firmness, consistency, cohesiveness and index of viscosity) of the investigated LB yogurt alternatives. Furthermore, LB yogurt alternatives out of UHT milk alternative revealed a lower tendency to syneresis, measured with siphon and centrifugation method. This work contributes to the fundamental knowledge of the textural properties of LB yogurt alternatives.

Unconventional Treatments of Food: Microwave vs. Radiofrequency

Abstract Food spoilage causes considerable economic losses and constitutes a health risk for consumers due to the potential for some microorganisms to produce toxins. In the last ten years, there are limitations in the microbial decontamination of foods by current methods and the development of novel techniques in this area would be advantageous. Conventional cooking and heating techniques produce the degradation of the product's quality attributes and nutritional properties due to the intense heat treatment and subsequent destruction of proteins and vitamins, including undesirable changes to other characteristics such as flavor and color. Dielectric heating has been studied in many experiments for microbial and pest reduction and for the ability to heat the product without making undesirable changes. The aim of this study is to make a short review in respect to unconventional treatments of food, which are already implemented in industry or are in the research and development phase. The paper presents similarities and differences between two novel treatments: microwave (MW) and radiofrequency (RF) in terms of equipment required, mechanism of action and applications in food industry.

Detection and characterisation of antimicrobial peptide produced by Bacillus subtilis FPTB23 isolated from curd

The growing consumer demand for finding natural but effective food preservation free of potential health risks has stimulated research in the field of biopreservation to find an attractive and alternative approach to chemical preservatives. Among the 51 colonies that displayed antibacterial activity against the indicator lawn of Staphylococcus aureus ATCC 25923, one colony isolated from curd, showed strong antimicrobial activity against the indicators tested, viz., Staphylococcus aureus (ATCC 25923), Enterococcus faecalis (MTCC 2729), Vibrio cholera and Vibrio parahaemolyticus . The isolate was identified as Bacillus subtilis by 16S rRNA gene sequencing and NCBI BLAST Analysis, having the Accession number KF556680. The neutralized cell free supernatant (NCFS) of isolate B. subtilis FPTB23 was able to inhibit the growth of S. aurus (ATCC 25923), E. faecalis (MTCC 2729), V. cholerae and V. parahaemolyticus inferring that the NCFS contains metabolites which is either a bacteriocin or bacteriocin like inhibitory substance. The strong antagonism against a number of serious and challenging foodborne pathogens/spoilage-causing micro-organisms advocated the high possibility of using this isolate as an effective preservative in food. The minimum inhibitory concentration (MIC) for the NCFS of Bacillus subtilis FPTB23 against Enterococcus faecalis (MTCC 2729) was found to be 200 AU/ml. The antimicrobial substance produced by B. subtilis FPTB23 was moderately heat stable, showed maximum activity at pH 7. The NCFS was completely inactivated after treatment with proteolytic enzymes such as, proteinase K and protease, which reveals the proteinaceous nature of the active substance. Exposure to Triton x-100, Tween 80, chloroform and butanol significantly decrease inhibition action. The molecular mass of the active form was found 21.5kDa by SDS-PAGE. The isolated species or its NCFS, therefore, can be used as food preservative reducing the requirement of intense heat treatments for foods to extend the shelf lives, thus, helping to maintain the freshness or unique texture of foods.

Acrylamide content and antioxidant capacity in thermally processed fruit products

Acrylamide as a known processing contaminant was determined in various heat-treated plum products purchased from a local market using LC/ESI-MS-MS. The highest level of acrylamide in the range up to 60 μg/kg was detected in a plum stew known as a "povidla", and in prunes, respectively. These products typically undergo intensive heat treatment that may take from several hours to days. Using a fruit dehydrator in home production of prunes, a low level of acrylamide under LOQ (15 μg/kg) was detected in comparison to most commercial products. Only in one of the prune samples from the market was the acrylamide content near to LOQ. The highest content of acrylamide (46 μg/kg) was detected in the Slovak sample of prune originated in Nitra region. High acrylamide content, in the range from 23 to 45 μg/kg, was observed in prunes from South America. In the rest of analysed heat-treated plum products such as plum juice, plum compote or baby food with plum puree, acrylamide was not detected due to moderate conditions during thermal processing: temperature below 120 °C and a shorter time of thermal exposure. The total phenolic content and antioxidant capacity of prunes were analysed using a UV-VIS-NIR spectrophotometer and an electron paramagnetic resonance (EPR) spectroscopy. Home-prepared prunes were characterized by the highest content of phenolics (4780 mg GAE/kg) and antioxidant capacity (14.6 mmol TEAC/kg). Commercial samples of prunes reached phenolics in the range from 1619 to 3461 mg GAE /kg, and antioxidant capacity was observed between 6.1 and 12.1 mmol TEAC/kg. Antioxidant capacity of prunes strongly correlated with total phenolic content and yellow and red colours measured in a CIELab system. However, no significant correlation between the acrylamide and antioxidative or organoleptic properties of prunes was observed. Moreover, it was noticed that bio production of plums did not demonstrate any positive impact on final acrylamide content or antioxidant capacity in comparison to conventional technology.

Stability of micronutrients and phytochemicals of grapefruit jam as affected by the obtention process.

Fruits are widely revered for their micronutrient properties. They serve as a primary source of vitamins and minerals as well as of natural phytonutrients with antioxidant properties. Jam constitutes an interesting way to preserve fruit. Traditionally, this product is obtained by intense heat treatment that may cause irreversible loss of these bioactive compounds responsible for the health-related properties of fruits. In this work, different grapefruit jams obtained by conventional, osmotic dehydration (OD) without thermal treatment and/or microwave (MW) techniques were compared in terms of their vitamin, organic acid and phytochemical content and their stability through three months of storage. If compared with heating, osmotic treatments lead to a greater loss of organic acids and vitamin C during both processing and storage. MW treatments permit jam to be obtained which has a similar nutritional and functional value than that obtained when using a conventional heating method, but in a much shorter time.

Tuning Physical Properties of Tomato Puree by Fortification with Grape Skin Antioxidant Dietary Fiber

Grape skins recovered from winemaking by-products were investigated for use as sustainable, antioxidant fiber-rich ingredient for the innovation of low-energy dense tomato puree. Six tomato purees fortified with grape skin antioxidant fiber, with varying particle size distribution, and two control tomato purees were studied. Physical parameters of purees were analyzed upon mixing and either an intensive heat treatment or an optimized heat treatment designed to achieve six decimal reductions of a target microorganism (Alicyclobacillus acidoterrestris) as recommended for pasteurization of acidic fruit products. Mixing of grape skin antioxidant fiber with tomato purees led to a decrease in both surface-weighted mean diameter (Sauter mean diameter, d(3,2)) and volume-weighted mean diameter (d(4,3)) values and an increase in span. Changes in these descriptors were most significant in purees added with the smallest particle sizes. Thermal stabilization of purees slightly decreased the d(3,2) values further and increased d(4,3) values, suggesting concomitant occurrence of particle disaggregation and formation of flocs within the food matrix. Phenolic solubility was inversely correlated to d(3,2) values. Bostwick consistency, storage (G′) and loss (G″) moduli, and complex viscosity (η*) increased in the fortified purees. The η* values displayed a positive correlation with d(4,3) values. Variations in Hunter colorimetric parameters were within the acceptability threshold. Overall, the information obtained provides knowledge to assist development of fiber-rich, low-energy dense fruit purees.

Impact of feed additives SUBACIL-1 and SUBACIL-2 on productivity of chicken-broilers

One of the most important problems of probiotics production is the development of non-waste technologies, in particular, usage of microbial cultures fugate. In conventional technology, it must be disposed of after the intensive heat treatment in drains. The fugate does not contain bacteria, but rather products of their metabolism and biosynthesis, which may have therapeutic, preventive and growth-stimulating effects. The above mentioned fact shows the relevance of the development of non-waste technology of feed probiotics of the genus Bacillus and their metabolites. In al-Farabi Kazakh National University, at Biotechnology Department of Faculty of Biology and Biotechnology were obtained experimental samples of probiotic feed additives – SUBACIL. SUBACIL-1 is lyophilized biomass of Bacillus subtilis P-2 containing 9х1012 spores in 1g. SUBACIL-2 is a combined feed probiotic comprising metabolites of B.subtilis P-2 immobilized on sunflower meal with addition of soya flour hydrolyzate. In this study was investigated the impact of feed additives SUBACIL-1 and SUBACIL-2 for growing of broiler chickens, in accordance with the following factors: changes of body weight, average daily gain and safety of the birds. The addition SUBACIL-1 of feeding for broilers increases the productivity of poultry meat by 11%, SUBACIL-2 – 9%. The use of new additives during the growing period is accompanied by the increase in average daily gain. When using of SUBACIL-1 daily gain is by 9.7% more than that of control group and 2.4% while using of SUBACIL-2. The introduction of these additives allows gaining 90% (SUBACIL-1) and 85% (SUBACIL-2) preservation of livestock. The greatest efficiency index was 214.94.

Modified peptides as indicators for thermal and nonthermal reactions in processed milk.

Site-specific relative quantification of β-lactoglobulin modifications in heated milk and dairy products was performed to determine their thermal and nonthermal origins and to evaluate marker candidates for milk processing. Therefore, formation kinetics of 19 different structures at 26 binding sites were analyzed by ultrahigh-performance liquid chromatography-tandem mass spectrometry with multiple reaction monitoring (UHPLC-MS/MS/MRM) after specific protein hydrolysis. The results indicate that (i) site-specific analysis of lactulosyllysine may be a more sensitive marker for mild heat treatment than its overall content; (ii) N(ε)-carboxymethyllysine, N-terminal ketoamide, and asparagine deamidation are of thermal origin and may be good markers for rather intensive heat treatment, whereas N(ε)-carboxyethyllysine reflects thermal and nonthermal processes; (iii) the relevance of methylglyoxal-derived arginine modifications is low compared to that of other modifications; (iv) oxidation of methionine and cysteine is a rather weak indicator of thermal impact; and (v) the tryptophan modifications formylkynurenine and kynurenine are of nonthermal origin and further degraded during processing.

The True Origin of Ductile Fracture in Aluminum Alloys

It has generally been assumed that metals usually fail as a result of microvoid nucleation induced by particle fracture. Here, we concentrate on high-density micropores filled with hydrogen in aluminum, existence of which has been largely overlooked until quite recently. These micropores exhibit premature growth under external loading, thereby inducing ductile fracture, whereas the particle fracture mechanism operates only incidentally. Conclusive evidence of a micropore mechanism is provided by the observation of an instantaneous release of gas at failure. We can therefore conclude that the growth of micropores dominates ductile fracture. Since the material we used has a standard pore density, we can assume that an identical fracture mechanism operates in other aluminum alloys. This finding suggests that intense heat treatment, which is generally believed to enhance the mechanical properties through homogenization, may have entirely the opposite effect. This revelation will have a major impact on the engineering design of metals.

Effects of fire on cation content in water: a laboratory simulation study

Laboratory experiments were carried out to explore the effect of thermal shocks (as occur during fire) and simulated rainfall events on cation leaching dynamics in an organic rich Leptic Umbrisol soil. The soil samples were collected in the field using specially designed lysimeter boxes that allow sampling and application of thermal shock treatments and simulated rainfall while keeping the soil structure unaltered. The soil temperature during the thermal shocks and degree-hours of accumulated heat were determined, and cation (Na+, K+, Ca2+ and Mg2+) leaching was measured in surface runoff (0-cm depth) and subsurface flow (12-cm depth) samples collected from the lysimeter boxes. Important differences were found in cation leaching in relation to thermal shock: monovalent cation leaching from the soil above 200°C (68 degree-hours) and divalent cations leaching above 220°C (195 degree-hours) was higher than that seen in other treatments. In general, the amount of cations leached increased with the severity of the thermal shock; however, under moderate conditions, there was a decrease in cation leaching, mainly of monovalent ions. The exchangeable cation losses by leaching in the intense heat treatments were ~80%.

OS1801 3D/4Dイメージングによるアルミニウム材料の破面解析

It has generally been assumed that metallic materials usually fail as a result of microvoid nucleation induced by particle fracture. In the present study, we examine this hypothesis by employing high-resolution 4D observations combined with the recently developed 4D image analysis method to correlate fracture surface to fracture origins embedded in materials before loading. All the dispersion particles embedded in the entire field of view (16,667 particles) were tracked during loading. The position coordinates of each fracture surface were tracked backward in time from the fracture surface image toward the initial unloading state on the basis of the scattered data interpolation with radial basis functions. It has been revealed that high density micro pores filled with supersaturated gas exhibit premature growth, thereby inducing ductile fracture, whereas the particle fracture mechanism operates only incidentally. This finding suggests that intense heat treatment, which is generally believed to enhance the mechanical properties of metallic materials, has entirely the opposite effect.

Effect of different temperature–time combinations on physicochemical, microbiological, textural and structural features of sous-vide cooked lamb loins

Lamb loins were subjected to sous-vide cooking at different combinations of temperature (60, 70, and 80°C) and time (6, 12, and 24h). Different physicochemical, histological and structural parameters were studied. Increasing cooking temperatures led to higher weight losses and lower moisture contents, whereas the effect of cooking time on these variables was limited. Samples cooked at 60°C showed the highest lightness and redness, while increasing cooking temperature and cooking time produced higher yellowness values. Most textural variables in a texture profile analysis showed a marked interaction between cooking temperature and time. Samples cooked for 24h showed significantly lower values for most of the studied textural parameters for all the temperatures considered. Connective tissue granulation at 60°C and gelation at 70°C were observed in the SEM micrographs. The sous-vide cooking of lamb loins dramatically reduced microbial population even with the less intense heat treatment studied (60°C–6h).

Effect of Processing and Cooking Conditions on Onion (Allium cepa L.) Induced Antiplatelet Activity and Thiosulfinate Content

Allium vegetables serve as sources of antiplatelet agents that may contribute to the prevention of cardiovascular disease. However, onion and garlic, the major Allium species, are usually cooked before consumption. Here, we examined the effect of cooking on onion in vitro antiplatelet activity (IVAA). Two different cooking systems (convection oven and microwaves) and several time-temperature variables were tested on whole bulbs, quarters of bulbs, and completely crushed bulbs, monitoring the degradation of sulfur antiplatelet compounds (e.g., thiosulfinates) by analysis of pyruvate levels. Although heating was, in general, detrimental for onion IVAA, the extent of this effect varied greatly, from unaffected antiplatelet activity (AA) (i.e., similar to raw onion) to a complete lost of activity, depending upon the manner in which onions were prepared prior to heating, the cooking method, and the intensity of the heat treatment. "Whole", "quarters", and "crushed" onions lost their IVAA after 30, 20, and 10 min of oven heating, respectively. The longer retainment of AA in intact bulbs was attributed to a later alliinase inactivation. Proaggregatory effects observed in samples subjected to the most intense oven and microwave heat treatments suggest that extensively cooked onions may stimulate rather than inhibit platelet aggregation. The efficacy of Allium species as antiplatelet agents, as affected by preparation and cooking conditions, is discussed.

Preparation and magnetic characterization of Co2-W strontium hexaferrites doped with Ni and La

The formation and magnetic properties of new Ni- and La-substituted SrCo2-W hexaferrites were investigated. Fabrication of single phase samples required undertaking composition and sintering conditions optimization. This process confirmed the production of W hexaferrites from intermediate cubic and hexagonal ferrite phases and additionally proved the enhancement of final purity by the excessive hexagonal component. Furthermore, according to the X-ray diffraction analysis, pure Ni- or La-doped compounds were formed in most cases, which actually necessitated more intense heat treatment (1225–1250°C). Yet, magnetic measurements interestingly reveal that substances with low substitution possess high saturation magnetization (∼72–75Am2/kg) and unexpectedly lower coercivity (∼28–46Oe), compared to the undoped one. This behavior is attributed to the chemistry of both substitutions, inducing the magnetic order variation and the anisotropy transition from in-plane to axial. Thus, a scarcely elaborated transient compositional region with planar anisotropy and strong magnetization is discerned, highlighting the potential of these soft ferrites.

Technological Strategies to Reduce Acrylamide Levels in Heated Foods

In April 2002, unexpectedly high levels of the neurotoxic and suspected carcinogen acrylamide were found in many heated foods, represented mainly by cereal and potato derivatives. Acrylamide can be formed during intense heat treatments as a consequence of the reaction between asparagine and a carbonyl source via Maillard-type reactions. Efforts by the scientific community have contributed to the identification of potential routes to reduce acrylamide levels in foods, and consequently, consumer intake. The main mitigations strategies, which can be applied to lower acrylamide content, include agronomical (i.e., selection of raw materials with low sugar and asparagine contents) and technological interventions (e.g., pretreatments, process, and formulation changes). This review explores the most reliable and potentially exploitable technological strategies for acrylamide reduction in food products. In order for an industrial process to be feasible it has to comply with the compatibility requisites of the existing process, as well as have low impact on sensory and nutritional properties of foods, regulatory compliance, and limited costs. In this regard, an innovative approach of physical removal of acrylamide from the finished product is also discussed.

Rheological properties of dairy desserts prepared in an indirect UHT pilot plant

Abstract The Viscolab (Tetra Pak), an indirect ultra-high treatment (UHT) pilot plant, was used to prepare dairy desserts containing kappa-carrageenan, skimmed milk powder (SMP), adipate cross-linked acetyl-substituted waxy maize starch, sucrose and water. Effects of varying concentrations of carrageenan, milk powder and starch on the dessert rheology were studied, while the sucrose and water content were kept constant. The rheological measurements included both small amplitude oscillation tests and large deformation penetration tests. To investigate the influence of shear during the process, the scraped-surface heat exchangers of the UHT pilot plant were run at two rotation speeds. At a low rotation speed of 70 rpm, both the complex modulus and gelation temperature were found to increase with increasing carrageenan content and upon substitution of SMP by starch. These findings are in line with the previously reported exclusion effect of starch, demonstrated by the authors for lab-scale and sterilized dairy desserts. However, more intense shearing at 350 rpm mainly affects the starch granules, which results in a lower complex modulus and gelation temperature of dairy desserts containing high amounts of starch. Where starch granules seem to considerably contribute to small oscillatory deformation measurements, they appear to contribute little to the gel strength. Compared to earlier reported lab-scale experiments, the dessert preparation in an UHT pilot plant involves a more intense heat treatment. As a result, a more extensive whey protein denaturation and subsequent complexation with casein micelles is believed to contribute to the rheological properties of the UHT desserts.