High Temperature Short Time Research Articles

Characterization of protein aggregates in cream and skimmed human milk after heat and high-pressure pasteurization treatments.

Preservation processes applied to ensure microbial safety of human milk (HM) can modify the native structure of proteins and their bioactivities. Consequently, this study evaluated the effect of pasteurization methods (Holder pasteurization, high-temperature short-time (HTST), and high hydrostatic pressure (HHP)) of whole human milk (HM) on protein aggregates in skim milk and cream fractions. For heat-treated whole milk, insoluble protein aggregates at milk fat globule membrane (MFGM) were formed by disulfide and non-covalent bonds, but insoluble skim milk protein aggregates were only stabilized by non-covalent interactions. Contrary to heat treatment, the insolubilization of main proteins at the MFGM of HHP-treated HM was only through non-covalent interactions rather than disulfide bonds. Moreover, only heat treatment induced the insoluble aggregation of ⍺-lactalbumin. Overall, compared to heat treatment, HHP produced a milder effect on protein aggregation, validating the use of this process to better preserve the native state of HM bioactive proteins.

Study on high temperature short time (HTST) hot air puffing of rice

Hot air puffing is the simplest, hazard- and contamination-free, and quickest method, wherein grains are suddenly exposed to a high temperature short time (HTST) process to get puffed. In this study, the continuous hot air puffing system was developed, comprising of grain feeder, heating chamber, puffing chamber, cyclone separator, and recirculation pipe. The experiments were conducted using Central Composite Rotatable Design (CCRD), on pre-processed rice (cv. MTU 1010), with one pre-heating pass of 11.50 s at 150 °C. The results showed that the puffed rice can be produced optimally at a pre-fixed whirling air velocity of 4.75 (± 0.25) m/s, puffing air temperature of 260 °C and with a feed rate of 6500 g/h, resulting in final moisture content (% db), expansion ratio, puffing percentage (%), whiteness index, hardness (kg) and crispness (+ve peaks) as 3.71, 5.68, 95.87, 69.82, 32.12 and 89.81, respectively. Further study on increased time of preheating upto 46 s (4 passes) at 150 °C keeping all other puffing parameters unchanged, showed that final moisture content (% db), expansion ratio, puffing percentage (%), and whiteness index were further improved like final moisture content reduced upto 2.68% db and expansion ratio, puffing percentage, whiteness index increased upto 7.35, 99.58% and 87.76, respectively. Thus, the rice puffing using a continuous hot air puffing system can be accomplished using 4 pre-heating passes (accumulative retention heating time of 46 s) at 150 °C, puffed using a hot air puffing system with whirling velocity of 4.75 m/s at a puffing temperature and feed rate of 260 °C and 6500 g/h.

Superior oxygen-resistance and intrinsic mechanisms of coherent Pd/Pd3Zr@ZrCo structure with excellent cycling durability

As a promising candidate for hydrogen isotopes storage, ZrCo alloy suffers tremendously from the poisoning of impurity gases, especially in oxygen-containing atmospheres, but related effective modification method for long cycling durability is still lacking. In this work, the anti-oxygen-poisoning behaviors and mechanisms of virginal ZrCo and palladium-coated ZrCo with different heating evacuation methods were detailly investigated. Notably, the phase transition occurs during traditional heating evacuation (550 °C for 60 min) with the gradual generation of Pd3Zr from original Pd coating and ZrCo substrate. According to absorption behaviors and degeneration state of O πp-orbital peak from theoretical calculations, O2 undergoes spontaneous dissociation and strong hybridization at the surface of ZrCo and Pd3Zr, especially for ZrCo, while much weak surface absorption is recognized on Pd. Considering the superior anti-poisoning properties but weak substrate anchoring strength of Pd, it’s valuable to reconstruct the Pd/ZrCo interface to generate transition Pd3Zr layer that is less susceptible to hydrogen embrittlement. Accordingly, a coherent structure of Pd/Pd3Zr@ZrCo was successfully obtained by high temperature short time pretreatment (550 °C for 10 min), and its cycling capacity retention in O2-containg hydrogen atmosphere is significantly enhanced from initial 74.87 % after 5 cycles to 90.83 % after 10 cycles, which is superior to Pd-plating hydrogen storage alloys ever reported. The interface reconstruction of coherent structure proposed here can function as a promising strategy for construction of protective layer for all related surface engineering.

Evaluating the UV-C sensitivity of Coxiella burnetii in skim milk using a bench-scale collimated beam system and comparative thermal sensitivity study by high-temperature short-time pasteurization

Introduction:Coxiella burnetii is a zoonotic Gram-negative obligate intracellular bacterial pathogen and the causative agent of query (Q) fever in humans. Contamination of milk by C. burnetii, as a consequence of livestock infection, is a significant public health concern. Effective methods to inactivate C. burnetii in milk are a critical aspect of food safety. Implementation of non-thermal UV-C processing technologies in the dairy industry can effectively preserve the sensory and nutritional quality of raw milk products while ensuring their safety, making them a viable alternative to traditional high-temperature short-time (HTST) pasteurization methods.Methods: Optical light attenuation factors, such as the absorption, scattering, and reflection by skim milk (SM) were evaluated using a spectrophotometer. SM inoculated with an avirulent strain of C. burnetii was irradiated using a collimated beam device equipped with a low-pressure UV-C 254 nm lamp at doses from 0 to 12 mJ/cm2. Optical properties were considered for the evaluation of the delivered UV-C dose. The pasteurization treatment was conducted using a lab scale HTST pasteurizer (72°C/15 s). The verification studies were conducted using Escherichia coli ATCC 25922 inoculated in a phosphate buffer (transparent fluid) and humic acid (opaque fluid). Salmonella enterica serovar Muenchen ATCC BAA 1674 inoculated in SM was tested for its suitability as a surrogate for C. burnetii, a bacterium that requires specialized equipment and expertise for experimentation.Results and Discussion: Absorption, reduced scattering coefficient, and the reflectance of SM at 254 nm were measured as 19 ± 0.3/cm, 26 ± 0.5/cm, and 10.6%, respectively. The UV-C results showed a log-linear inactivation of C. burnetii in SM with the UV-C sensitivity (D10) value of 4.1 ± 0.04 mJ/cm2. The results of HTST pasteurization revealed that C. burnetii was heat-sensitive with a D value of 1.75 min. Salmonella Muenchen showed similar UV inactivation kinetics and is, thereby, suggested as a suitable surrogate to C. burnetii for the pilot-scale UV-C processing studies of SM.

Comparative Analysis of Pulsed Electric Fields (PEF) and Traditional Pasteurization Techniques: Comparative Effects on Nutritional Attributes and Bacterial Viability in Milk and Whey Products

With the current upsurge in the desire to foster healthy lifestyles and consume nutritious food products, the food industry has been propelled to develop novel food processing technologies. In our study, we critically evaluated the influence of pulsed electric field (PEF) processing by comparing it to conventional thermal pasteurization protocols—low temperature, long time (LTLT), high temperature, short time (HTST), and microfiltration (MF)—and its ramifications on the nutritional properties inherent in raw milk, which comprises vitamins, whey protein, amino acids, cholesterol, and fatty acids. A significant difference in β-lactoglobulin content was observed in PEF-treated liquid whey samples compared to those treated with high-temperature (HT) pasteurization, where 4.8-fold reduction with a concentration of 0.80 mg/mL was observed. Liquid whey samples treated with PEF, LTLT, HTST and MF retained β-lactoglobulin content, PEF-treated samples yielded 3.85 mg/mL, while HTST, LTLT, and MF-treated samples had β-lactoglobulin content of 3.62 mg/mL, 3.63 mg/mL, and 3.62 mg/mL compared to raw whey control (RWC) at 3.81 mg/mL. The concentrations of nutritional properties, like vitamins (A, D, E), amino acids, cholesterol, and fatty acids, remained approximately consistent across all the pasteurization methodologies. Moreover, the bacterial viability in the context of various pasteurization methodologies was scrutinized, with an absence of colonies observed in whey specimens subjected to thermal pasteurization. PEF-treated samples exhibited a substantial 1.6-log reduction in coliform colony count to less than 4 CFU/mL after curd reduction, in contrast to raw milk samples.

Homogenization and thermal processing reduce the concentration of extracellular vesicles in bovine milk.

Extracellular vesicles (EVs) in bovine milk confer beneficial physiologic effects to consumers. Industrial processing treatments may affect the amount or bioactivity of EVs intrinsic to bovine milk. We investigated how the content and concentration of EVs were affected by homogenization and thermal processing of raw bovine milk. Raw milk was processed by homogenization, low-temperature (LT) heat, or pasteurization [high-temperature short-time (HTST) and ultra-high-temperature (UHT)] in a pilot processing facility. EVs were isolated from the raw and processed bovine milk using differential ultracentrifugation and quantified using a nanoparticle tracking analyzer. Bovine milk EVs were assessed for total miRNA and protein concentrations standardized to particle count using a fluorometric assay. There were 1.01 × 1010 (±3.30 × 109) EV particles per ml of bovine milk. All industrial processing treatments caused >60% decrease in EV concentration compared to the raw bovine milk. Homogenization and heat treatments independently and additively reduced the content of EVs in bovine milk. The averages of total miRNA/particle and total protein/particle concentrations were elevated threefold by low-temperature heat-processing treatment relative to HTST and UHT pasteurizations. The average diameter of EVs was reduced by 11%-16% by low temperature compared to raw milk (127 ± 13 nm). Homogenization and pasteurization indiscriminately reduce the EV concentration of bovine milk. Smaller EVs with higher protein content resist degradation when processing bovine milk at sub-pasteurization temperature. This new foundational knowledge may contribute to food product development on the preservation of EVs in processed dairy products, including bovine milk-based infant formulas that some newborns are dependent on for adequate growth and development.

Gram-negative postpasteurization contamination patterns of single-serve fluid milk produced in 4 different processing facilities

An analysis of historic data on high temperature, short time (HTST) fluid milk quality showed higher total bacterial counts and lower sensory defect judging scores at d 14 post-processing for milk packaged in single-serve containers as compared with milk packaged in half-gallon containers from the same processing facilities. As post-pasteurization contamination with gram-negative bacteria is likely a major contributor to an increased spoilage risk associated with milk packaged in single-serve containers, we performed a comprehensive assessment of the microbial quality and shelf-life of 265 commingled single-serve HTST fluid milk samples (including white (unflavored) skim, white (unflavored) 1%, chocolate skim, and chocolate 1%) collected over 2 visits to 4 commercial fluid milk processing facilities. Over 2 initial sampling visits, the frequency of gram-negative spoilage ranged from 14 to 79% of the product collected from the 4 facilities, with significant differences of gram-negative spoilage frequency between sampling visits, facilities (sampling visit 1, sampling visit 2, and both sampling visits combined), milk types (sampling visit 2), and filler lanes (sampling visit 2). There were no significant differences in the frequency of gram-negative spoilage between sampling time points (e.g., beginning, middle, and end of production run). Across facilities, single-serve containers of milk with gram-negative contamination showed significantly higher bacterial counts on d 7 and 14 and significantly lower sensory scores as compared with those without gram-negative contamination. Follow-up investigations, based on in-facility surveys that identified carton forming mandrels as filler components that frequently failed quality assurance ATP swab checks, found that bacterial genera, including Pseudomonas and Bacillus, isolated from single-serve milk samples were also frequently isolated from mandrels. While interventions aimed at improving cleaning and sanitation of mandrels did not lead to significant reduction of gram-negative spoilage frequency in a comparison of 398 control and 400 intervention samples, our data still suggest that the unhygienic design of single-serve fillers is likely a root-cause of gram-negative contamination of single-serve milk.

Microbacterium represents an emerging microorganism of concern in microfiltered extended shelf-life milk products

Growing interest in the manufacture of extended shelf-life (ESL) milk, which is typically achieved by a high temperature treatment called ultra-pasteurization (UP), is driven by distribution challenges, efforts to reduce food waste, and more. Even though high temperature, short time (HTST) pasteurized milk has a substantially shorter shelf-life than UP milk, HTST milk is preferred in the United States because consumers tend to perceive UP milk as less desirable due to the "cooked" flavor associated with high-temperature processing. While ESL beyond 21 d may be possible for HTST, the survival and outgrowth of psychrotolerant aerobic spore-forming bacteria can still be a limitation to extending shelf-life of HTST milk. Microfiltration (MF) is effective for reducing vegetative microorganisms and spores in raw milk, but it is unclear what the effects of membrane pore size, storage temperature, and milk type (i.e., skim vs whole) are on the microbial shelf-life of milk processed by both MF and HTST pasteurization. To investigate these factors, raw skim milk was MF using different pore sizes (0.8 μm or 1.2 μm), and then MF skim milk and standardized whole milk [MF skim with heat-treated (85°C for 20 s) cream] were HTST pasteurized at 75°C for 20 s. Subsequently, milk was stored at 3, 6.5, or 10°C and total bacteria counts were measured for up to 63 d. An ANOVA indicated that mean bacterial concentrations between storage temperatures were significantly different from each other, with mean maximum observed concentrations of 3.67, 5.33, and 8.08 log10 cfu/mL for storage temperatures 3, 6.5, and 10°C, respectively. Additionally, a smaller difference in mean maximum bacterial concentrations throughout shelf-life was identified between pore sizes (<1 log cfu/mL), but no significant difference was attributed to milk type. An unexpected outcome of this study was the identification of Microbacterium as a major contributor to the bacterial population in MF ESL milk. Microbacterium is a psychrotolerant, thermoduric gram-positive, non-spore forming rod with a small cell size (∼0.9 μm length and ∼0.3 μm width), which was able to permeate the membranes used in this study, survive HTST pasteurization, and then grow at refrigeration temperatures. While spores continue to be a key concern for the manufacture of MF, ESL milk, our study demonstrates the importance of other psychrotolerant, thermoduric bacteria such as Microbacterium to these products.

Towards excellent strength-ductility synergy via high temperature short time annealing in low-carbon ultrafine grain steel

A new ar-chitecture of ultrafine grain (UFG) steel with coarsen bimodal size distribution was realized by high-temperature short time annealing process. Abundant comparisons on ferrite size, precipitates, and dislocation were performed with previous works. In the present study, the synthetical mechanical properties showing a tensile strength of 974.9 ± 27.1 MPa and 18.5 ± 1.66% elongation in UFG steel with grain size of 374 nm was enhanced without much strength sacrifice. High-temperature short time annealing process promoted the intragranular Nb(C, N) particles formation and the recrystallization ferrite coarsening. However, the better work hardening ability confirmed by the increased intragranular Nb(C, N) particles dominated the synthetical mechanical properties in UFG steel. The intragranular Nb(C, N) particles advocated the stimulation and accumulation of geometrically necessary dislocations (GNDs), thus the strength increment by work hardening counteracted the decreased strength resulted from coarsen ferrite grains.

Analysis of the Responses to Pasteurization Temperatures of Methicillin Resistant Staphylococcus aureus Derived from Milk Items

Background and Aim: One of the leading causes of both community- and hospital-acquired infections is the superbug," multidrug-resistant Staphylococcus aureus (MRSA). Milk and dairy products seem to be highly vulnerable to a wide range of diseases. Therefore, we require processing procedures that both eliminate pathogens and lengthen the useful life of these products. The purpose of this study was to determine how susceptible MRSA isolates were to pasteurization temperatures after being recovered from dairy products.&#x0D; Materials and Methods: For the purpose of pasteurization, ten MRSA isolates were exposed to both a 63°C LTLT (low temperature, long time) therapy for 30 minutes and a 72°C HTST (high temperature, short time) treatment for 16 seconds.&#x0D; Results: The findings indicated that all isolates were killed by a pasteurization-like treatment at low temperature for a long time (63°C for 30 minutes), but that particular adaptable isolates could survive a pasteurization-like treatment at high temperature for a short time (72°C for 16 seconds), which may point to a time- and temperature-dependent variation in the thermal tolerance mechanism.&#x0D; Conclusion: The results showed that all isolates seemed extremely susceptible to damage from heat using LTLT pasteurization-like treatment (63°C for 30 minutes). Nevertheless, a particular number of these isolates succeeded in establishing colonies because they have quorum sensing structures that survive being handled by using heat damage at 72°C for 16 seconds. Pasteurized milk producers should be alerted to the fact that this microorganism has been found in contaminated milk since it compromises the product's safety and diminishes its value to consumers. As a result, it is strongly advised that manufacturers utilize varied temperatures for milk processing in order to remove the contaminating methicillin- and heat-resistant S. aureus (MHRSA).

Development and deployment of a supply-chain digital tool to predict fluid-milk spoilage due to psychrotolerant sporeformers

Psychrotolerant sporeformers pose a challenge to maintaining fluid milk quality. Dynamic temperature changes along the supply chain can favor the germination and growth of these bacteria and lead to fluid milk spoilage. In this study, we aim to expand on our previous work on predicting milk spoilage due to psychrotolerant sporeformers. The key model innovations include (i) the ability to account for changing temperatures along the supply chain, and (ii) a deployed user-friendly interface to allow easy access to the model. Using the frequencies and concentrations of 8 Bacillales subtypes specific to fluid milk collected in New York, the model simulated sporeformer growth in half-gallons of high-temperature short-time (HTST) pasteurized fluid milk transported from processing facility to retail store and then to consumer. The Monte Carlo simulations predicted that 44.3% of half-gallons of milk were spoiled (defined as having a bacterial concentration > 20,000 cfu/mL, a conservative estimate that represents the Pasteurized Milk Ordinance [PMO] regulatory limit) after 21 d of refrigerated storage at consumer's home. Model validations showed that the model was the most accurate in predicting the mean sporeformer concentration at low temperatures (i.e., at 3 and 4°C; compared with higher temperatures at 6 and 10°C) within the first 21 d of consumer storage, with a root mean square error of 0.29 and 0.34 log10cfu/mL, respectively. Global sensitivity analyses indicated that home storage temperature, facility-to-retail transportation temperature, and initial spore concentration were the 3 most influential factors for predicting milk spoilage on d 21 of shelf-life. What-if scenarios indicated that microfiltration was predicted to be the most effective strategy to reduce spoilage. The implementation of this strategy (assumed to reduce initial spore concentration by 2.2 log10cfu/mL) was predicted to reduce the percentage of spoiled milk by 17.0 percentage points on d 21 of storage and could delay the date by which 50% of half-gallons of milk were spoiled from d 25 to d 35. Overall, the model is readily deployed as a digital tool for assessing fluid milk spoilage along the supply chain and evaluating the effectiveness of intervention strategies, including those that target storage temperatures at different supply chain stages.

Covalent Adduct Formation between β-Lactoglobulin and Flavor Compounds under Thermal Treatments That Mimic Food Pasteurization or Sterilization.

Thermal processing (e.g., pasteurization and sterilization) is a critical step ensuring the microbial safety of our foods. Previous work from our laboratory has examined the covalent reactions occurring between proteins and a broad selection of flavor compounds under ambient storage temperatures (25-45 °C). However, similar research on reactions of flavor compounds with a protein under thermal processing conditions has not been investigated. In the current study, covalent adduct formation between β-lactoglobulin (BLG) and 46 flavor compounds encompassing 13 different classes of functional groups was investigated under pasteurization and sterilization conditions by UPLC-ESI-QTOF-MS. BLG was chosen as a representative protein for this study because it is structurally well characterized, its molecular weight is well suited for ESI-MS analysis (18.2 kDa), and it is broadly used in the food industry. Schiff base, aza-Michael addition, and disulfide linkages were the main types of covalent interactions occurring across the reactive samples. Among them, isothiocyanates, aldehydes, and thiol-containing compounds were generally very reactive. Increasing the severity of the thermal treatment [high-temperature-short-time (HTST) pasteurization, in-container pasteurization (IC), and ultra-high-temperature (UHT) sterilization conditions] accelerated the reactions of BLG with flavor compounds, which revealed reactivity of three flavor compounds not previously observed to react at room temperature (eugenol, 4-vinyl phenol, and 3-nonen-2-one). Ketones [other than 2-hydroxy-3-methyl-2-cyclopenten-1-one (cyclotene), diketones, and unsaturated ketones], alcohols, acids, alkenes (terpenes), esters, lactones, 3-acetylpyridine, methyl anthranilate, vanillin, 2-methylthiophene, and dimethyl sulfone did not show measurable reactivity with BLG under the thermal processing conditions examined. An overall view of the data shows that the HTST heat treatment (72 °C for 15 s) had the least effect on the extent of reaction while in-container pasteurization conditions (63 °C for 30 min) produced a similar extent of reaction as the UHT (130 °C 30 s) heat treatment. These varying extents of adductation are in reasonable accord with what one might expect, given that the rates of most classes of chemical reactions occurring near ambient temperature increase by a factor of 2-4 for each increase of 10 K in temperature. Unfortunately, our methodology did not permit us to obtain meaningful data using the most aggressive standard sterilization thermal conditions (110 °C for 30 min) because extensive aggregation/coagulation removed essentially all of the BLG protein from the reaction mixtures prior to MS analysis.

Effect of popping and milling on physical, chemical, structural, thermal properties and angle of repose of amaranth seed (Amaranthus cruentus L.) and finger millet (Eleusine coracana L. Gaertn) from Udhagamandalam

The study was conducted to examine the effect of popping and milling on selected properties of amaranth and finger millet from Udhagamandalam. The amaranth and finger millet are cleaned, popped at high temperature for short time in an open pan method, and pulverised using a mixer at the laboratory. Water activity had decreased as the heat processing had reduced the bound water content 0.53 to 0.23. Alcoholic acidity had elevated levels in popped and pulverised grains in comparison to native grains. Grains showed a major change in surface area and porosity in the range of 0.12 to 1.20 m2/g and 3.20 to 4.54 Å. The intensity of the colour had shown higher in amaranth samples and lower on finger millet upon processing in the range of 44-74 L*, 4-7 a* and 2.8-11.6 b*. Crystallinity had shifted from A-shaped curves to a single V curve during processing. The native material underwent various treatments and decreased apparent and compact bulk density in comparison to native grains significantly from 0.82 to 0.14 and 0.69 to 0.35 in amaranth and finger millet respectively. The processing has improved overall physio-chemical properties.

Physicochemical analysis as food safety in pasteurized milk in CV. Cita Nasional

Milk is an animal-source food that has a high nutritional with contains 2.8% protein, 3.0% fat, vitamin A, B, C, D, and others. CV. Cita Nasional is one of the dairy processing industries that produces pasteurized milk products. The purpose of this study was to analyze food safety by conducting physicochemical testing of pasteurized milk products with the types HTST (High-Temperature Short Time) or LTLT (Low-Temperature Long Time). The research method used was physicochemical testing on the finished product of pasteurized milk including pH, Fat, Total Solid, Brix and Organoleptic. Physicochemical testing was done by comparing the finished product data in CV. Cita Nasional with the Indonesian National Standard (SNI) data. The Mann-Whitney Test was used for the data analysis. The results showed a significant value for the variables of temperature 0.565; pH 0.104; Fat 0.001; Total Solid 0.000 and brix 0.000. Based on the data analysis results, the overall significance value was <0.05, which means that the Mann-Whitney Test showed a positive effect on the physicochemical quality and that the physicochemical test of pasteurized milk products meets the requirements of SNI.

A Review on The Improvement of Extruded Food Processing Equipment: Extrusion Cooking in Food Processing

The extrusion technique, which combines mixing, shaping, texturing, and heating to create a unique food product, is gaining popularity in the worldwide agro-food processing sector. Extrusion cooking is a high-temperature, short-time (HTST) method that kills bacteria and inactivates enzymes. Compared to conventional cooking, extrusion cooking is favored because of its high productivity and substantial nutrient retention. Extrusion technology has become an essential tool in the food processing industry with its various benefits over other processing methods. It is a low-cost approach that provides a platform for processing a variety of items from several food categories by altering major or minor components and processing conditions. Extrusion technique is used in the food sector to create a wide range of supplemental foods, pet foods, morning cereals, pasta, snacks, and other textured foods. It's a low-cost method of reintroducing food processing waste and by-products into the food supply. Extrusion technology's flexibility allows for the production of value-added products and nutritionally dense fortified goods using various low-cost raw ingredients. Extruded goods are microbiologically safe, have a longer shelf life, and have less moisture content. This technology's advantages include product diversity and excellent quality and new food productivity and low processing time.

Concentration of milk oxylipins after heat and homogenization treatments

Heat treatment and homogenization of milk are common processing steps intended to reduce microbial load for safe human consumption, and to avoid creaming, respectively. Although the effects of combined pasteurization and homogenization on free fatty acids (FFA) and lipid oxidation markers such as hydroperoxides, and thiobarbituric acid reactive species (TBARS) have been well characterized, their effects on primary oxidized fatty acids known as oxylipins have not yet been determined. This study aimed to determine the effects of two heat treatments: milk pasteurization [high-temperature short time, 72°C for 15 s (HTST)] and sterilization [ultra-high temperature, 135°C for 3 s (UHT)] with or without homogenization (10, 17 or 24 MPa) on FFA (%), primary (hydroperoxides and oxylipins) and secondary oxidation compounds (TBARS). Heat treatments alone significantly reduced most oxylipins compared with raw milk, but did not alter % FFA, hydroperoxide, and TBARS levels. The combination of UHT and homogenization at 24 MPa increased % FFA, hydroperoxide value, and some oxylipins, compared to raw milk and other treatments. Overall, the combination of heat treatment and homogenization significantly increased oxylipin formation compared with heat treatment alone.

T15 High Speed Steels Produced by High-Temperature Low-Pressure Short-Time Vacuum Hot-Pressing Combined with Subsequent Diffusion-Bonding Treatment

Currently, hot isostatic pressing (HIP) is widely used to produce highly alloyed high speed steels (HSSs) in an industrial scale; however, the HIP’s production cost is very high. Another powder consolidation approach with low production cost, namely vacuum hot-pressing (VHP), has hitherto received limited attention. The present work aims to develop an innovative solid-state VHP approach, producing HSSs with large cross-sectional sizes via a VHP facility having low loading capacity, thus further decreasing production cost. In doing so, VHP is performed at a sufficiently high temperature such that the pressure leading to full densification can be significantly reduced to a magnitude as low as several MPa; simultaneously, VHP is completed within a timeframe as short as several seconds to minutes, retaining fine carbide sizes; subsequently, the as-VHP HSS is diffusion-bonding treated (DBT-ed) at a relatively low temperature, achieving full metallurgical bond between powders while minimizing carbide growth. In the present work, T15 HSS was processed using the above VHP approach. The VHP temperature as high as 1200 °C was selected and consequently, the minimal pressure leading to full densification was decreased to ~7 MPa. By controlling displacement of pressing punch to a value corresponding to full densification, the VHP was competed for only 15 min. The almost fully dense as-VHP T15 HSS exhibits submicrometric carbide sizes smaller than those in the as-HIP counterpart, but incomplete metallurgical bond between powders. After diffusion bonding treatment at a relatively low temperature of 1100 °C for 2–4 h, the extent of metallurgical bond between powders is significantly enhanced with insignificant carbide growth. After regular quenching and tempering, the VHP plus DBT-ed T15 HSSs exhibit smaller average primary carbide sizes and similar hardness and three-point bend fracture strength, relative to those in the HIP counterpart after similar quenching and tempering.

Effects of ultrasound combined technology on quality and volatile compound properties of chili sauce

In this study, the effect and mechanism of seven kinds of sterilization treatments, including ultrasound (US), pasteurization (PT), high temperature short time (HTST), hot air (HA), microwave (MW), ultraviolet (UV) and steam sterilization, on E. coli, S. aureus and P. aeruginosa were investigated. It was found that PT, HTST, MW, and steam sterilization gave ideal bactericidal effect and were subsequently, combined with ultrasound treatment and applied to chili sauce. The results showed that ultrasound combined with microwave (US + MW) treatment was effective in preserving the maximum nutritional value and flavor of chili sauce while ensuring its sterility. The total number of colonies and coliforms were not detected after US + MW treatment. Furthermore, the contents of total polyphenol, capsaicin and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging ability in the US + MW group were 11.10%, 12.78% and 17.00% higher than those of traditional autoclave sterilization. In addition, polyphenol oxidase (PPO) activity was 2.04 times higher in the US + MW group compared to the autoclave sterilization group. Correlation analysis showed that total polyphenol and capsaicin were positively correlated with 2,2′-azino-bis(3-ethylbenzothiazoline)-6-sulphonic acid (ABTS) (correlation coefficients 0.90 and 0.76, respectively) and DPPH free radical scavenging ability (correlation coefficients 0.88 and 0.72, respectively). The results obtained from GC-MS showed that US + MW treatment could reduce the loss of volatile compounds and retained the original flavor of chili sauce. The content of diallyl disulfide was 1.8 times that of autoclave group. This study provides a new theoretical reference for sterilization and flavor preservation of chili sauce.

Effect of dipotassium phosphate and heat on milk protein beverage viscosity and color

Our objective was to determine the effect of addition of dipotassium phosphate (DKP) at 3 different thermal treatments on color, viscosity, and sensory properties of 7.5% milk protein-based beverages during 15 d of storage at 4°C. Micellar casein concentrate (MCC) and milk protein concentrate (MPC) containing about 7.5% protein were produced from pasteurized skim milk using a 3×, 3-stage ceramic microfiltration process and a 3×, 3-stage polymeric ultrafiltration membrane process, respectively. The MCC and MPC were each split into 6 batches, based on thermal process and addition of DKP. The 6 batches were no postfiltration heat treatment with added DKP (0.15%), no postfiltration heat without added DKP (0%), postfiltration high-temperature, short time (HTST) with DKP, postfiltration HTST without DKP, postfiltration direct steam injection with DKP, and postfiltration direct steam injection without DKP. The 6 MCC milk-based beverages and the 6 MPC milk-based beverages were stored at 4°C. Viscosity, color, and sensory properties were determined over 15 d of refrigerated storage. MCC- and MPC-based beverages at 7.5% protein with and without 0.15% added dipotassium phosphate were successfully run through an HTST and direct steam injection thermal process. The 7.5% protein MCC-based beverage contained a higher calcium and phosphorus content (2,425 and 1,583 mg/L, respectively) than the 7.5% protein MPC-based beverages (2,141 and 1,338 mg/L, respectively). Pasteurization (HTST) had very little effect on beverage particle size distribution, whereas direct steam injection thermal processing produced protein aggregates with medians in the range of 10 and 175 μm for MPC beverages. A population of casein micelles at about 0.15 μm was found in both MCC- and MPC-based beverages. Larger particles in the 175-μm range were not detected in the MCC beverages. In general, the apparent viscosity (AV) of MCC beverages was higher than MPC beverages. Added DKP increased the AV of both MCC- and MPC-based beverages, while increasing heat treatment decreased AV. The AV of beverages with DKP increased during 15 d of 4°C of storage for both MCC and MPC, whereas there was very little change in AV during storage without DKP and a similar effect was observed for sensory viscosity scores. The L value of beverages was higher with higher heat treatment, but DKP addition decreased L value and sensory opacity greatly. Sulfur-eggy flavors were detected in MPC beverages, but not MCC-based beverages.

Effect of Direct Steam Injection and Instantaneous Ultra-High-Temperature (DSI-IUHT) Sterilization on the Physicochemical Quality and Volatile Flavor Components of Milk.

The effects of variations in the heat treatment process of milk on its quality and flavor are inevitable. This study investigated the effect of direct steam injection and instantaneous ultra-high-temperature (DSI-IUHT, 143 °C, 1-2 s) sterilization on the physicochemical properties, whey protein denaturation (WPD) rate, and volatile compounds (VCs) of milk. The experiment compared raw milk as a control with high-temperature short-time (HTST, 75 °C 15 s and 85 °C 15 s) pasteurization and indirect ultra-high-temperature (IND-UHT, 143 °C, 3-4 s) sterilization. The results showed no significant differences (p > 0.05) in physical stability between milk samples with different heat treatments. The DSI-IUHT and IND-UHT milks presented smaller particle sizes (p < 0.05) and more concentrated distributions than the HTST milk. The apparent viscosity of the DSI-IUHT milk was significantly higher than the other samples (p < 0.05) and is consistent with the microrheological results. The WPD of DSI-IUHT milk was 27.52% lower than that of IND-UHT milk. Solid-phase microextraction (SPME) and solvent-assisted flavor evaporation (SAFE) were combined with the WPD rates to analyze the VCs, which were positively correlated with ketones, acids, and esters and negatively associated with alcohols, heterocycles, sulfur, and aldehydes. The DSI-IUHT samples exhibited a higher similarity to raw and HTST milk than the IND-UHT samples. In summary, DSI-IUHT was more successful in preserving the milk's quality due to its milder sterilization conditions compared to IND-UHT. This study provides excellent reference data for the application of DSI-IUHT treatment in milk processing.