Effects of foam-mat drying temperature on physico-chemical and microstructural properties of shrimp powder

This study was carried out to investigate the impact of different drying air temperatures (45, 60, 75, and 90 °C) on the physico-chemical and microstructural properties of foam-mat-dried shrimp powder. Physico-chemical properties such as moisture content, water activity, solubility, water binding capacity (WBC), and color of the powder were determined. The experimental results showed that as the temperature increased, the moisture content, water activity, and WBC of the samples decreased. However, their solubility increased significantly (p < 0.05). Furthermore, the total color difference (ΔE) increased by increasing temperature, yet decreased at 90 °C. The SEM images indicated as the drying temperature increased, the mat structure porosity increased, too, especially at 90 °C.Industrial RelevanceThe demand for ready-to-eat (RTE) and/or ready-to-cook (RTC) meals is gradually growing because they are easy to prepare. The dried shrimp powder can be used for producing formulated seafood and other food products such as soups, sauce, snacks, etc. to increase the protein content and improve the nutritional value of them. Fish and shrimp soup mixes and snacks are examples of dried RTE products. They are popular in Asian countries, due to easy transportation, quality, stability, and long shelf life.     

Rheology of mozzarella cheese

The rheological properties of mozzarella cheese were studied by using a parallel plate, a sliding plate, an extensional and a capillary rheometer over a temperature range of 25–60 °C. While mozzarella cheese behaves as a semisolid at room temperature, it behaves mostly as a liquid at higher temperatures (typically greater than 40 °C). The rheological data obtained from the various pieces of rheometers were compared. Differences among the various data sets were observed and these were demonstrated to be due to the inherent changes to the material structure during testing and to the changes in the physical properties of the cheese at different temperatures. Mozzarella cheese is a viscoelastoplastic material at room temperature, which becomes viscoelastic at about 60 °C. Its yield stress gradually decreases with increase of temperature pointing to structural changes that occur at elevated temperatures. A Herchel–Buckley viscoplastic rheological model was found to describe adequately its rheology.     

Stability of probiotic Lactobacillus plantarum in dry microcapsules under accelerated storage conditions

This study investigated the stability of freeze dried and fluid bed dried alginate microcapsules coated with chitosan containing model probiotic bacteria, Lactobacillus plantarum, during storage for up to 45 days at different water activities (0.11, 0.23, 0.40 and 0.70) and temperatures (4, 30 and 37 °C). The loss in cell viability was around 0.8 log in the case of fluid bed drying and around 1.3 in the case of freeze drying, with the former method resulting in dried capsules of smaller size (~ 1 mm vs 1.3 mm), more irregular shape, and with a rougher surface. In both cases, the water activity and water content were less than 0.25 and 10% w/w, respectively, which favours high storage stability. The storage stability studies demonstrated that as the water activity and temperature decreased the survival of the dried encapsulated cells increased. Considerably better survival was observed for fluid bed dried encapsulated cells compared to freeze dried encapsulated cells and freeze dried free cells with 10% sucrose (control), and in some cases, e.g. at 4 and 30 °C at water activities of 0.11, 0.23 and 0.40, there was more than 1 log difference after 45 days, with concentrations higher than 10⁸ CFU/g after 45 days of storage. The results indicate that fluid bed drying is an effective and efficient manufacturing method to produce probiotic containing capsules with enhanced storage stability.     

Effects of drying conditions on some physical properties of soy protein films

The influence of drying conditions (air temperature and relative humidity) on mechanical properties, solubility in water, and color of two kinds of soy protein isolate film: a commercial one (CSPI) and other obtained under laboratory conditions (LSPI) were evaluated using the response surface methodology (RSM). Soy protein films were prepared by casting using glycerol as plasticizer. The films were dried in a chamber with air circulation under controlled conditions of relative humidity (24%, 30%, 45%, 60%, 66%) and air temperature (34, 40, 55, 70, 76 °C). It was verified that mechanical properties of films made from LSPI and CSPI are influenced in a very different way by the drying conditions due to a diverse initial protein conformation in both materials, as was revealed by DSC and SDS–Page studies. The solubility of the LSPI film was affected by temperature and relative humidity, being lowest (～50%) for films obtained at high RH and temperatures ranging from 45 to 76 °C. For CSPI films, in contrast, solubility did not depend on the drying process and it remained relatively constant (～40%). The optimal drying conditions determined by RSM were: 70 °C and 30% RH for CSPI films and 60 °C and 60% RH for LSPI films. Dried under these conditions, CSPI films presented a higher tensile strength, lower elongation at break, lower solubility and better water and oxygen permeability than LSPI ones.     

The drying kinetics of kale (Brassica oleracea) in a convective hot air dryer

The effect of air temperature and sample thickness on the drying kinetics of kale was investigated using a convective air dryer at a fixed airflow rate of 1 m/s and drying air temperatures of 30, 40, 50 and 60 °C. The sliced kale leaves were dried in wire trays in 10, 20, 40 and 50 mm thick layers. The drying rate increased with drying air temperature but decreased with layer thickness. The effective diffusivity for 10 mm thick layers was found to increase with the drying air temperature and ranged between 14.9 and 55.9 × 10⁻¹⁰ m²/s. The effect of temperature on diffusivity could be expressed by an Arrhenius type relationship with a high R² of 0.9989. The activation energy of kale was found to be 36.115 kJ/mol. When four drying models were developed using the experimental data the Modified Page model was found to be marginally better than the other models in estimating the drying curve over the experimental temperature range.     

An investigation into lactose crystallization under high temperature conditions during spray drying

Lactose crystallization was studied at high temperature conditions in a Buchi B-290 mini spray dryer. The inlet gas temperature was 200 °C, and an insulating material was used to reduce the heat loss from the drying chamber (outlet temperature 157 °C), thus increasing the gas and particle temperatures. At these conditions, lactose crystallinity was found to increase significantly compared with a case where it was spray dried at 170 °C in a non-insulated drying chamber (outlet temperature 90 °C), but the process yield was lower for the former case (0.16% yield) than for the low temperature conditions (47% yield). There is some evidence that high-temperature spray drying of lactose is more likely to give more β-lactose anomer. Different analytical techniques (Fourier Transform Infrared Spectroscopy, modulated differential scanning calorimetry, moisture sorption test, Raman spectroscopy) were used to investigate the degree of crystallization and possible lactose anomer formation during this spray drying at high inlet gas temperatures.     

Ohmic heating and pulsed vacuum effect on dehydration processes and polyphenol component retention of osmodehydrated blueberries (cv. Tifblue)

Blueberries are highly perishable fruits; therefore, emerging technologies focus on improving the bioactive compound retention and extending the shelf life. The aim of this study was to evaluate the effect of ohmic heating and vacuum pulses on the dehydration processes and polyphenol compound retention of osmodehydrated blueberries (cv. Tifblue). The treatments were performed using a 65% (w/w) sucrose solution, an electric field of 13 V/cm (100 V) at 30 °C, 40 °C or 50 °C for 300 min, and air drying at 50, 60 or 70 °C to obtain dried blueberries. The moisture content, soluble solids and phenolic compounds were analyzed. The combination of ohmic heating/pulsed vacuum treatments intensifies mass transfer in osmodehydrated blueberries, especially at higher temperatures. Nevertheless, the polyphenol retention was greater at lower temperatures; hence, the application of an intermediate process temperature (40 °C) was selected as a pre-treatment prior to further drying. The treated samples improve the retention of polyphenols after drying compared with untreated samples. Therefore, the results of this research study suggest that the use of a pulsed vacuum and ohmic heating in the osmotic dehydration (PVOD/OH) treatment at 40 °C for 240 min and subsequent drying at 60°C could be the best process for dehydrating blueberries, considering that it improved mass transfer, achieved lower losses of phenolic components and reduced the drying time.Industrial relevanceBlueberries are an important fruit due their high bioactive compound content, especially polyphenols. Studies that involve emerging technologies application could add value to blueberries. Ohmic heating and pulsed vacuum as pre-treatments improve the efficiency of dehydration processes, focused toward bioactive compounds retention and achieving commercial viability. In this work have been applied PVOD/OH treatments at moderated temperatures and subsequently dried at 60 °C, obtaining promissory results.     

Radiant energy under vacuum (REV) technology: A novel approach for producing probiotic enriched apple snacks

The feasibility of vacuum impregnation in combination with air drying + radiant energy vacuum (REV) drying to produce shelf stable probiotic enriched apple slices was evaluated. The shelf life of the products was monitored at 25 and 4 °C. The results demonstrated that bacterial stability at 25 °C depended on the dehydration techniques; with the longest shelf life in air drying +REV drying followed by freeze drying and air drying. Storage at 4 °C showed no significant changes in bacterial population up to 180 days in all samples. Sensory properties of the air drying +REV and freeze dried apple slices remained above the acceptable level for 30 days at 25 °C and 180 days at 4 °C. The results also revealed that dried apple slices were able to provide prominent protection to the cells in acidic gastric juice.     

Studies on the steady shear flow behavior and functional properties of Lepidium perfoliatum seed gum

Flow properties of Lepidium perfoliatum gum, extracted from Qodume shahri seeds, as influences of concentrations (0.5%, 1%, 1.5% and 2%), temperatures (5, 25, 45, and 65 °C), salts and pHs were investigated. Among the selected models, power law model well described the rheological behavior of the L. perfoliatum seed mucilage solutions with high determination coefficients, R² and low root mean square error (RMSE). Non-Newtonian shear thinning behavior was observed at all temperatures and concentrations. While increase in temperature decreased the viscosity and increased the flow behavior indices, adverse effect was obtained by increasing the concentration. The temperature effect was more pronounced at 0.5% L. perfoliatum seed gum concentration and indicated the higher activation energy (E_a: 31614.56 J/mol). The viscosity was dependent on type of salt addition, and decreased with salt concentration. This behavior was more evident when using divalent salt. A marked dependence of viscosity on pH was also observed, as pH increased from acidic to alkaline conditions, the viscosity increased until pH of 9 and afterward decreased. The hydrocolloid showed good water absorption capacity (WAC) and imparted relatively high stability to foam and oil-in-water emulsion. However, the gum solubility was low at all temperatures studied (30, 60 and 90 °C).     

Effects of combined pretreatments on drying kinetics and quality of potato chips undergoing low-pressure superheated steam drying

Due to an increasing demand from health-conscious consumers more attention has been placed on investigating alternative techniques to replace conventional deep-fat frying to produce health-friendly snack products including potato chips. Recently, low-pressure superheated steam drying (LPSSD) has proved to have potential to produce fat-free potato chips if performed in combination with appropriate pre-drying treatments. In this study, the influences of various pretreatments and drying temperature on the LPSSD drying kinetics and quality parameters of dried potato chips were investigated. LPSSD of potato chips underwent various combined pretreatments, i.e., (a) blanching, (b) combined blanching and freezing, (c) blanching followed by immersion in glycerol solution and then freezing, and (d) combined blanching, immersion in monoglyceride solution and freezing, were carried out at different drying temperatures (70, 80, and 90 °C) at an absolute pressure of 7 kPa. The quality of the dried chips was then evaluated in terms of colors, texture (hardness, toughness and crispness) and microstructure. In terms of the drying behavior and the dried product quality, LPSSD at 90 °C with combined blanching and freezing pretreatments was proposed as the most favorable conditions for drying potato chips.     

Effect of drying temperature and beeswax content on moisture isotherms of whey protein emulsion film

The objective of this investigation was to study the effect of drying temperature and beeswax (BW) content on moisture sorption behavior of whey proteins emulsion films. For this purpose, films were obtained by the casting method and dried at two selected temperatures (5 and 25 °C) and constant relative humidity (RH) (58%). After drying, films were removed from the casting plates and were conditioned in the environmental chamber set at 25 °C and 58% RH for 3 days. Subsequently, portions of 400 mg of film were placed in glass bottles and pre-dried in desiccators containing drierite (a_w=0) during 10 days. Then, the bottles were placed in hermetically sealed glass jars containing 10 different desiccants to achieve a_w ranging from 0.11 to 0.90, and allowed to reach equilibrium. The analyses were made in quintuplicate at 25 °C. The equilibrium moisture content (EMC) was determined by drying samples in an oven and the experimental data were fitted by the Brunauer-Emmett-Teller (BET) and the Guggenheim-Anderson-De Boer (GAB) models. The results showed that both models were effective to describe the moisture sorption behavior of the films. The GAB model gave better fit than the BET model. The increase of the drying temperature of 5 to 25 °C and the incorporation of lipids reduced the EMC of whey protein emulsion films. Finally, data from experimental sorption isotherms are a useful tool to predict the effect of the environmental conditions that surround the film on its properties; particularly considering that the stability of an edible film is function of its mechanical and moisture barrier properties and both are strongly influenced by the presence of water, film formulation and drying and storage conditions.     

Effect of Season and Stage of Lactation on Performance of Holsteins

Ninety-seven Holstein cows were used to evaluate the effects of season and stage of lactation on physiological measurements, behavior, and milk production. Skin and rectal temperatures and respiration rates were lowest in winter and highest in summer. Skin temperatures increased .39°C per degree rise in ambient temperature, whereas rectal temperature and respiration rate changed .017°C and 1.74 breaths/min per degree increase in air temperature. Eating activity in winter was 5.6 h and decreased to 4.2 h during summer. Lying activity decreased from winter to summer, whereas standing activity increased. Drinking, defecation, and urination frequency increased from winter to summer. Monthly milk yield was highest during the spring and lowest in winter. Highest milk yield for early and midlactation cows was in the spring, whereas late lactation cows performed best in the summer. Midlactation cows were most adversely affected by summer conditions, and early and late lactation cows were most affected by winter conditions. These data show differential response of cows in different stages of lactation to changes in the environment.     

Effect of heating on the stability of grape and blueberry pomace procyanidins and total anthocyanins

Fruit by-products are rich sources of procyanidins and anthocyanins known for potential health benefits. Freeze dried blueberry pomace and grape pomace were heated in a forced air oven at 40, 60, 105, and 125 °C for 72, 48, 16, and 8 h respectively, to study the stability of procyanidins and total anthocyanins. Heating decreased procyanidin concentrations significantly (p < 0.05) in both blueberry and grape pomace, except when heated at 40 °C for 72 h. Reduction occurred when heated at 60 °C or above with no further reduction when heating temperature increased from 105 to 125 °C. Heating also affected total anthocyanin contents in both grape and blueberry pomace with no significant (p > 0.05) loss when heated at 40 °C. Total anthocyanin loss was highest at 125 °C for both blueberry (52%) and grape pomace (70%). Results suggested that while heating at lower temperatures for up to 3 days may not be detrimental, heating at higher temperatures for more than 8 h results in considerable loss of both the compounds.     

Effects of exopolysaccharide-producing strains of Streptococcus thermophilus on technological and rheological properties of set-type yoghurt

This study investigated the effects of two Streptococcus thermophilus strains, ST 285 and ST 1275, on selected technological and rheological characteristics of set-type yoghurt. The strains were selected for their capability to produce distinctly different exopolysaccharides (EPS) and were thus coded as capsular (ST 285) or ropy-capsular (ST 1275). The culture performance and physico-chemical properties of yoghurt were assessed in relation to different fermentation temperatures (30, 37 or 42 °C) and prolonged storage (up to 30 days) at low temperature (4 °C). ST 1275 showed faster growth and acidification rates, resulting in yoghurt with lower syneresis and higher-flow behaviour index, than ST 285. EPS production appeared to be growth associated with the maximum given at growth temperatures of 37 and 42 °C for ST 285 and ST 1275, respectively; however, EPS concentration declined considerably during storage. Prolonged cold storage increased several rheological characteristics of yoghurt including G′, consistency index and hysteresis loop area. A weak correlation between EPS concentration and textural properties of yoghurt was observed.     

Manufacture of lignin microparticles by anti-solvent precipitation: Effect of preparation temperature and presence of sodium dodecyl sulfate

An anti-solvent precipitation technique was explored for the ability to produce lignin microparticles. An aqueous–organic solution of lignin was dispersed into a much larger volume of water, whereby leaching of organic solvent from the dispersed phase into the water resulted in progressive precipitation of the lignin solute, ultimately producing a suspension of hardened microparticles. Temperature and addition of surfactant were investigated as a means of controlling particle properties. Increasing initial water temperature between 4 and 80 °C produced increasingly large agglomerates of uniform sub-micron primary particles, increasingly fused into monolithic masses. Although the glass transition temperatures of dried lignins were in the range of 75–87 °C, depression of glass transition temperature in the presence of water during particle formation may be associated with the increasing agglomeration of particles with increasing temperature. Incorporating sodium dodecyl sulfate (SDS) in the water at temperatures of 20–60 °C inhibited agglomeration producing smooth, spherical, monodisperse particles in the range of 0.1–0.2 μm. However, SDS concentrations greater than 1% caused the formation of some larger particles. Once safety, consumer acceptance and aspects of functionality have been established, spherical particles in the 0.1–0.2 μm size range may have application as food industry fat mimetics, fillers or even as solid particle emulsifiers.Industrial relevanceIncreased biorefining of lignocellulosic feedstocks to produce bioethanol may lead to an abundance of lignin that could be well-utilised as a sustainable, non-caloric food ingredient. Microparticulation provides a route for the transformation of lignin into a useful food ingredient, on the basis that particles with suitable properties for use in food systems can be produced: notably, a particle diameter preferably between 0.1 and 25 μm, spherical shape and stability against aggregation.     

Some physico-chemical,functional and rheological properties of actomyosin from green mussel (Perna viridis)

The physico-chemical and rheological properties of fresh actomyosin from green mussel (Perna viridis) have been evaluated. Amino acid profile of actomyosin revealed a relatively high proportion of glutamic acid, alanine, tryptophan and aspartic acid. Ultraviolet absorption spectra of actomyosin solution showed a maximum absorbance in the wavelength region of 270–280 nm indicating presence of aromatic amino acid residues. Dynamic viscoelastic behavior of actomyosin revealed the ability to form network during heating, however, the strength of network appeared to be weak as given by frequency sweep of the heat set gel. The flow behavior of actomyosin solution indicated pseudoplastic behavior at different concentrations and temperatures. Casson and Herschel-Bulkley models were used to evaluate flow behavior of actomyosin and revealed maximum yield stress value at 30 mg/ml at 40 °C.     

Sensory shelf-life predictions by survival analysis accelerated storage models

An Arrhenius model and survival analysis are introduced to analyze data based on consumers acceptance or rejection of samples stored at different times and different temperatures. Sample data comprises 60 consumers who observed raw minced beef samples stored at 2 °C, 9 °C and 19 °C, with seven different storage times for each temperature, answering yes or no as to whether they would accept the samples. An activation energy of 15.3 kcal/mol was estimated from this censored data set, and shelf-life predictions for temperatures outside the tested temperature range were obtained. In the present study it was found that experimental storage at three temperatures was necessary to obtain satisfactory shelf-life estimations for temperatures outside the tested range.     

Application of ohmic heating/vacuum impregnation treatments and air drying to develop an apple snack enriched in folic acid

The changes of lifestyle and eating habits of consumers have induced a growth in the demand for functional food. The aim of this work was to study the incorporation of folic acid into apple slices by using ohmic heating (OH) and vacuum impregnation (VI) at 30, 40 and 50 °C and air drying at 50, 60 and 70 °C to obtain an apple snack that is rich in folic acid. The kinetic impregnation of folic acid, texture and color were evaluated. The impregnated samples (VI) at 40 °C and vacuum-impregnated samples with ohmic heating (VI/OH) at 50 °C presented a high content of folic acid, whereas the samples air dried at 60 °C presented an important retention of folic acid. The lowest loss of firmness and color was obtained with the VI/OH treatment at 50 °C with drying at 60 °C. Therefore, the VI/OH treatment at 50 °C followed by drying at 60 °C was determined to be the best process for creating dehydrated apple slices that are rich in folic acid.Industrial relevanceThe aim of this research was to study the incorporation of folic acid into dehydrated sliced apples by using vacuum impregnation/ohmic heating (VI/OH) treatments and air drying technologies and evaluating the mechanical and optical properties of the resulting product. Two technologies, vacuum impregnation (VI) and ohmic heating (OH) were performed at 30, 40 or 50 °C with an electric field intensity of 13 V/cm using conventional heating. The results showed that the samples impregnated of apple slices by VI and VI/OH treatments reached the highest content of folic acid. However, the samples that were dried at 60 °C after impregnation by the VI/OH treatment at 50 °C exhibited an increase in folic acid due to the electropermeabilization effect, which induces retention of folic acid and an increase in the folic acid concentration by decreasing the water content. Under the investigated conditions, the VI/OH treatment at 50 °C followed by air drying at 60 °C may be considered the best processing method to obtain an apple snack that is rich in folic acid.     

Effect of processing conditions on the structure of monostearin–oil–water gels

The effect of processing conditions on the formation and stability of a gel comprised of oil, water, monostearin and stearic acid was studied. Processing conditions (homogenization rate (10,000–30,000 rpm), cooling rate (0.05–20 °C/min), homogenization temperature (70–95 °C)) had no effect on the initial storage modulus and melting temperature of the gel. Salt (NaCl) addition to the aqueous phase in the range 0–0.25% did not affect these parameters either; however, 0.5% salt addition lead to a ∼2 °C decrease in melting temperature and a doubling of the storage modulus. Optimal preparation conditions for the gel were mainly determined from its microstructure by polarized light microscopy – a smaller globule size and a more homogenous size distribution were considered a desirable feature. Optimum conditions included homogenization rates greater than 20,000 rpm, cooling rates above 6 °C/min, homogenization temperatures above, but close to, the Krafft temperature of monostearin (72 °C), and 0% salt concentration. The gelation temperature decreased by 2 °C with each 1 °C/min increase in cooling rate, from 1 °C/min to 5 °C/min.     

Heat transfer modeling of chicken cooking in hot water

To calculate the slowest heating point and optimum cooking time of whole chicken cooking in hot water, a 2-dimensional heat transfer model was developed to predict temperature profile and history of the chicken cooked in hot water at 85, 90 and 95 °C. Chickens were divided into 12 sections and the heat transfer model was applied to each cross section. These models were solved with an I-DEAS program. Specific heat and thermal conductivity were measured at temperatures ranging from 25 to 95 °C. The temperature of chicken did not significantly affect the thermal properties. The average values of specific heat of white and dark meats were 3.521 and 3.654 kJ/(kg K), respectively, and the average thermal conductivity values were 0.5093 and 0.4930 W/(m K), respectively. The model was validated against experimental results, and provided an average root mean square error of 2.8 °C. Temperature distributions showed that the slowest heating point was deep in the breast part of the second cross section (3.6 cm far from shoulder) at the symmetric line of the chicken, around 2.1–2.5 cm deep from breast skin. For food safety consideration, the recommended cooking times, for whole chickens in weight range of 2.3–3.2 kg with different initial temperatures (5–30 °C), were around 74–84, 64–74 and 57–67 min for cooking temperatures of 85, 90, and 95 °C, respectively.