Determination of optimum hazelnut roasting conditions

The objective of this study was to test the hypothesis that the roasting conditions used for hazelnuts, such as the air temperature, air velocity and roasting time (independent variables), could be optimized by using Response Surface Methodology. Effects of independent variables on sensory and physical characteristics were determined. A consumer test was used to determine the acceptable samples. Very dark and very light roasted samples, corresponding to 165 °C, 3 m/s, 25 min and 125 °C, 1 m/s, 15 min process conditions, respectively, were unacceptable. Superimposed contour plots were used to determine the values of independent variables and these showed the process conditions where all product characteristics were acceptable to consumers. At low velocity (0.3 m/s), acceptable products were produced at about 165–179 °C for 20–25 min. When air velocity increased, air temperature shifted to lower temperatures. Samples roasted at 145 °C, 2 m/s, 28 min, 165 °C, 1 m/s, 25 min and 145 °C, 3.7 m/s, 20 min produced the most acceptable products. The sample roasted at 165 °C, 1 m/s, 25 min required the least air velocity and was the most economical in terms of energy consumed among the samples rated most acceptable by consumers.     

Oil Migration in Chocolate–Peanut Butter Paste Confectionery as a Function of Chocolate Formulation

ABSTRACT:  Migration of oil from high oil content filling to the chocolate coating can result in undesirable quality changes in filled chocolate confectionery products. The objective of this study was to monitor and model peanut oil migration in a 2-layer chocolate–peanut butter paste model confectionery. Spatial and temporal oil content changes were evaluated using magnetic resonance imaging. Five formulations of chocolate, which varied in chocolate particle size, milk fat content, and emulsifier level, were assessed at 2 temperatures, 20 and 30 °C. The spatial and temporal experimental data were modeled using a Fickian-based diffusion model, fitting for the diffusion coefficient, D , over a time frame of 17 d. Values of the diffusion coefficient ranged from 1.82 to 3.23 × 10⁻¹¹ m²/s for the chocolate formulations stored at 30 °C. No significant mass transfer took place in the 20 °C samples over the experimental time frame. This study describes the dynamic nature of the interface between the chocolate and peanut butter paste layers, quantifies the mass transfer from the peanut butter paste to the chocolate, and reinforces the importance of temperature control.     

Enhancement of human fibroblast growth and other dermatological effects induced by cell extract from heat-shocked blue green alga (Cyanobacteria)

It has been known that high amounts of 'heat shock proteins (HSPs)' are produced under heat and other environmental stresses in cells. Recently, it was reported that HSP could also be accumulated in some dermal cells to protect the cellular proteins from damage caused by ultraviolet radiation. Here, the authors have focused on thermophilic cyanobacteria and the heat shock treatment. Thermophilic cyanobacteria are known to thrive under extreme environmental conditions, and produce distinctively high amounts of HSP when exposed to higher temperatures. We tested cell extract from heat-shocked cyanobacterial cells on a number of skin-related biological activities and found it significantly effective. The cyanobacterial cells, originally collected from a spa as hot as 55 °C, were cultivated in the laboratory at 50 °C and broken by a freeze-fracture method. The extract thus obtained had a superoxide dismutase (SOD)-like activity and inhibited lipid peroxide formation. We found that the extract obtained from the heat-shocked (at 63 °C) cells showed a much stronger SOD-like activity, while the inhibitory effect on lipid peroxide formation remained almost the same. Furthermore, the SOD-like activity could withstand heat up to 70 °C for as long as 1 h. Most remarkably, supplementing this heat-shocked extract strongly promoted the proliferation of human dermal fibroblast culture. Extracts from the cells grown at a regular temperature (50 °C) did not promote the proliferation of the fibroblasts. The heat-shocked extract was fractionated by ultrafiltration for further analysis. A fraction (molecular weight: 10 000–30 000) has shown the strongest activity so far. These results indicate that the heat-shocked cyanobacterial extract with its increased amounts of HSPs is a promising potent ingredient for anti-aging cosmetic materials.     

Inactivation of Vibrio parahaemolyticus and Vibrio vulnificus in oysters by high-hydrostatic pressure and mild heat

Several recent outbreaks associated with oysters have heightened safety concerns of raw shellfish consumptions, with the majority being attributed to Vibrio spp. The objective of this study was to determine the effect of high-hydrostatic pressure (HHP) followed by mild heating on the inactivation of Vibrio parahaemolyticus and Vibrio vulnificus in live oysters. Inoculated oysters were randomly subjected to: a) pressurization at 200–300 MPa for 2 min at 21 °C, b) mild heat treatment at 40, 45 or 50 °C for up to 20 min and c) pressure treatment of 200–300 MPa for 2 min at 21 °C followed by heat treatment at 40–50 °C. Counts of V. parahaemolyticus and V. vulnificus were then determined using the most probable number (MPN) method. Pressurization at 200–300 MPa for 2 min resulted in various degrees of inactivation, from 1.2 to >7 log MPN/g reductions. Heat treatment at 40 and 45 °C for 20 min only reduced V. parahaemolyticus and V. vulnificus by 0.7–2.5 log MPN/g while at 50 °C for 15 min achieved >7 log MPN/g reduction. HHP and mild heat had synergistic effects. Combinations such as HHP at 250 MPa for 2 min followed by heat treatment at 45 °C for 15 min and HHP at 200 MPa for 2 min followed by heat treatment at 50 °C for 5 min reduced both V. parahaemolyticus and V. vulnificus to non-detectable levels by the MPN method (<3 MPN/g). HHP at ≥275 MPa for 2 min followed by heat treatment at 45 °C for 20 min and HHP at ≥200 MPa for 2 min followed by heat treatment at 50 °C for 15 min completely eliminated both pathogens in oysters (negative enrichment results). This study demonstrated the efficiency of HHP followed by mild heat treatments on inactivation of V. parahaemolyticus and V. vulnificus and could help the industry to establish parameters for processing oysters.     

Methyl jasmonate coupled with modified atmosphere packaging to extend shelf life of tomato (Lycopersicon esculentum Mill.) during cold storage

The effects of methyl jasmonate coupled with modified atmosphere packaging (MJ+MAP) on the quality and shelf life of mature green tomato ( Lycopersicon esculentum Mill.) were investigated during cold storage at 5 °C. Tomatoes were treated with 10⁻⁴  m MJ and packaged under 5%O₂/5%CO₂/90%N₂ in a plastic bag. The effects of MJ+MAP were compared with control as well as heat treated (HT) samples. Control samples were tomatoes packaged under atmospheric air. HT samples were prepared by dipping tomatoes in hot water at 50 °C for 3 min and packaged under atmospheric air. The results showed that MJ+MAP and HT could delay ethylene production during tomato ripening and consequently slowed down the softening rate. MJ+MAP tomatoes showed better quality and less chilling injury (CI) symptoms than HT and control samples. Based on a nine-point score, shelf life criteria assumed that rejection would occur when the sensory attributes declined below 5. Control and HT overall acceptance scores were shown to fall below 5 scores after 3 and 6 weeks storage, while MJ+MAP had overall acceptance scores above 5 for up to 9 weeks. Control and HT samples could be stored for about 4 and 6 weeks, respectively, while MJ+MAP tomatoes could be stored for up to 9 weeks.     

Growth and Survival Differences of Vibrio vulnificus and Vibrio parahaemolyticus Strains during Cold Storage

ABSTRACT:  Vibrio vulnificus  and  Vibrio parahaemolyticus  are the most common  Vibrio  species associated with seafood illness in the United States. Our study was conducted to determine if strain-to-strain differences exist in the growth and survival of 8 different  V. vulnificus  and  V. parahaemolyticus  strains at low temperatures. By day 10,  V. vulnificus  strain 515-4C2 had significantly higher counts ( P  < 0.05) (1.97 log CFU/g) compared with strains 3315, 1007, 29306 at 5 °C, which reached nondetectable levels. At 8 °C, strain 515-4C2 had significantly higher counts ( P  < 0.05) (2.23 log CFU/mL) compared with 1007, 33815, 541(O) 49C, which reached nondetectable levels. At 10 °C, only  V. vulnificus  strain 33815 reached nondetectable levels. At 5 °C,  V. parahaemolyticus  strain 541(O) 57C had the highest counts (5.28 log CFU/g) by day 10 while strain 33847 had significantly lower counts (3.46 log CFU/g). After 10 d at 8 °C,  V. parahaemolyticus  strain M350A had the highest counts (7.97 log CFU/mL) while strain 541(O) 57C had the lowest counts (4.80 log CFU/mL). At 10 °C,  V. parahaemolyticus  strain NY477 had significantly higher counts ( P  < 0.05) with 8.31 log CFU/mL compared with strain 33847, which had the lowest counts (6.77 log CFU/mL). Our research has shown that various  V. vulnificus  and  V. parahaemolyticus  strains vary in their ability to survive and grow at refrigeration temperatures.     

Microbiological, physicochemical and organoleptic changes in dry-salted olives of Thassos variety stored under different modified atmospheres at 4 and 20 °C

Microbiological, physico-chemical and organoleptic changes were studied in dry-salted olives, cv. Thassos, stored under different atmospheres (100% carbon dioxide and nitrogen, 40% CO₂/30%O₂/30%N₂ and air) at 4 and 20 °C for 180 days. The initial microbial flora comprised of yeasts, no lactic acid bacteria, enterobacteria, pseudomonads or Staphylococcus aureus were detected, as the low water activity/high salt content does not favour their growth. At 4 °C, the population of yeasts declined steadily throughout storage but to a different extent depending on the gaseous atmospheres. At 20 °C, there was an initial decline in yeast counts in all samples followed by a steady increase until the end of the storage period. The CO₂ atmosphere was most effective at keeping the number of yeasts low at both storage temperatures. All gas atmospheres prevented fungal growth at both temperatures apart from the samples stored in air. The pH, a_w and salt content of the olives did not change significantly throughout the storage period. The prevailing yeast species was the salt tolerant Candida famata . The organoleptic characteristics did not differ significantly among differently treated olives. However, increased rancidity and reduced fruit colour was observed in the samples stored at 20 °C.     

Autolysis and biochemical properties of endogenous proteinases in Japanese sandfish (Arctoscopus japonicus)

Autolysis of Japanese sandfish ( Arctoscopus japonicus ) was studied. The highest autolysis was observed at 60 °C. Optimal pH for autolysis was found at both acidic and alkaline pH values. Autolytic activity decreased with increasing NaCl concentration. Further assay of the extract from Japanese sandfish exhibited the maximum activity at 55 °C and pH 9.5. The Japanese sandfish proteinases were markedly inhibited by pepstatin A at pH 3.5, while soybean trypsin inhibitor, PMSF and TLCK inhibited activities of proteinases at pH 9.5, suggesting Japanese sandfish proteinases were both aspartic and serine proteinases. The extracts were stable to heat treatment up to 50 °C for 15 min and still remained high relative activity after incubated at 50 °C for up to 8 h. Maximum stability of the extracts was observed between pH 6 and 11 and no changes of activity were found after incubation at pH 9.5 for up to 8 h. Activity of Japanese sandfish extract continuously decreased as NaCl concentration increased (0–30%), while activity increased as CaCl₂ concentration increased. The results suggest that major proteinases in Japanese sandfish were trypsin-like serine proteinases.     

Hot air drying of whole fruit Chinese jujube (Zizyphus jujuba Miller): thin-layer mathematical modelling

Chinese jujube fruits were dried at 50, 60 and 70 °C in an electric heat blast dryer. Verma model was superior to the others for explaining change of moisture ratio in Chinese jujube by comparing thirteen commonly used mathematical models, suggested by the lowest percent error (1.211%). A strong linear dependence between drying rate and drying time was suggested by high values of determination coefficient ( R ² > 0.97). Linear model (effective diffusivity model) was found to be excellent adequacy in describing relationship between effective diffusivity, D _eff, and dry-basis moisture content, M . The effects of drying air temperature on the coefficients of the model were determined by multiple regression method. Lower percent error (3.44%) proved that the effective diffusivity model has higher precision. Our study indicated that it is possible to describe moisture content, drying rate, effective diffusivity, with the models including the effect of drying air temperature on the model constants and coefficients.     

Modeling Heat Transfer During Oven Roasting of Unstuffed Turkeys

A finite element method was used to solve the unsteady state heat transfer equations for heating of turkeys in a conventional electric oven. Breast, and thigh and wing joint temperature in 5.9, 6.8, 8.6, 9.5, and 10.4 kg turkeys were simulated. A surface heat transfer coefficient of 19.252 W/m2K determined by transient temperature measurements in the same oven, was used. Thermal conductivity measured using a line heat source probe from 0 to 80°C was 0.464 W/mK. Simulated temperatures were within 1.33, 1.47, and 1.22°C of experimental values of temperature in the breast, thigh, and wing joint, respectively. Initial temperature 1,2, and 3°C lower than 4°C required additional baking time of 16,22, and 27 min., respectively for the thigh joint to reach the target endpoint temperature.     

Effects of mild heat treatment on microbial growth and product quality of packaged fresh-cut table grapes

ABSTRACT:  The changes in packaged fresh-cut grape quality and microbial growth as affected by mild heat treatments and the retention of grape cap stems during 5 °C storage were evaluated. Each individual grape was either manually pulled off (stemless) from the stems, or cut (cut stem) to allow for a 1- to 2-mm cap stem remaining on the berry. The samples were sanitized in 100 mg/L chlorine solution for 1 min, followed by a mild heat treatment in a water bath (45 °C, 8 min) or an oven (55 °C, 5 min). After cooling, the berries were packaged in rigid trays sealed with a gas permeable film and stored at 5 °C. Product quality and decay rate were evaluated periodically during storage. The results indicate that in the package headspace for hot water treatment of stemless grapes, partial pressures of O₂ declined significantly ( P < 0.05) less and C₂H₄ increased significantly ( P < 0.001) less than for the control and hot air treatment. Stem removal and heat treatment had significant ( P < 0.05) effects on the decay rate of grapes during storage. Hot water treatment maintained a significantly lower decay rate than the control and hot air treatment throughout the entire storage. Color and texture were not significantly ( P > 0.05) affected by either heat treatment or stem removal. Grapes that retained the cap stems and received hot water treatment had the lowest decay rate and lowest microbial growth with the absence of any negative impact on grape color, texture, and flavor.     

IMPINGEMENT DRYING OF POTATO CHIPS

The effect of superheated steam temperature (115, 130, and 145C) and convective heat transfer coefficient (100 and 160 W/m²C) on the drying rate and product quality attributes (shrinkage, density, porosity, color, texture, and nutrition loss) of potato chips was investigated. Furthermore, potato chips dried by impinging superheated steam (130 and 145C, h = 100 W/m²C) were compared to air dried (same conditions), commercial, and fried potato chips. Temperature and convective heat transfer coefficient had a significant effect on the drying rate during superheated steam impingement drying. Potato chips dried at higher drying temperature and convective heat transfer coefficient showed less shrinkage, lower bulk density, higher porosity, and darker color when compared to chips dried at lower temperatures and convective heat transfer coefficients. They were also less hard and had a lower vitamin C content. A higher rate of evaporation during the falling rate period was obtained when superheated steam drying was compared to air impingement drying. Potato chips produced using superheated steam impingement drying showed more shrinkage, higher bulk density, lower porosity, and lighter color than chips dried with air under the same temperature and with the same convective heat transfer coefficient (130, and 145C, h = 100 W/m²C). Moreover, superheated steam‐dried potato chips retained more vitamin C during the drying process.     

Effects of pH and temperature on inactivation of Salmonella typhimurium DT104 in liquid whole egg by pulsed electric fields

Pulsed electric field (PEF) exposes a fluid or semi-fluid product to short pulses of high-energy electricity, which can inactivate microorganisms. The efficacy of PEF treatment for pasteurisation of liquid eggs may be a function of processing temperature. In this study, effects of PEF, temperature, pH and PEF with mild heat (PEF + heat) on the inactivation of Salmonella typhimurium DT104 cells in liquid whole egg (LWE) were investigated. Cells of S. typhimurium were inoculated into LWE pH adjusted to 6.6, 7.2 or 8.2 at 15, 25, 30 and 40 °C. The PEF field strength, pulse duration and total treatment time were 25 kV cm⁻¹, 2.1 μs and 250 μs respectively. Cells of S. typhimurium in LWE at pH 7.2 were reduced by 2.1 logs at 40 °C and 1.8 logs at 30 °C. The PEF inactivation of S. typhimurium cells at 15 or 25 °C was pH dependent. Heat treatment at 55 °C for 3.5 min or PEF treatment at 20 °C resulted in c. 1-log reduction of S. typhimurium cells. Combination of PEF + 55 °C achieved 3-log reduction of S. typhimurium cells and was comparable to the inactivation by the heat treatment at 60 °C for 3.5 min. With further development, PEF + heat treatment may have an advantage over high-temperature treatment for pasteurisation of liquid eggs.     

Optimization of pressure-induced germination of Bacillus sporothermodurans spores in water and milk

Bacillus sporothermodurans produces highly resistant endospores that can survive ultra-high-temperature treatment in milk. The induction of endospore germination before a heat treatment could be an efficient method to inactivate these bacteria and ensure milk sterility. In this work, the rate of spore germination of B. sporothermodurans LTIS27 was measured in distilled water after high-pressure treatments with varying pressure (50–600 MPa), treatment temperature (20–50 °C), pressure-holding time (5–30 min) and post-pressurization incubation time (30–120 min) at 37 °C or 4 °C. The results showed that pressure-induced germination was maximal (62%) after a treatment at 200 MPa and 20 °C and increased with pressure-holding time and post-pressurization incubation time. Treatment temperature had no significant effect on germination. A central composite experimental design with three factors (pressure, pressure-holding time, and post-pressurization incubation time) using response surface methodology was used to optimize the germination rate in distilled water and in skim milk. No factor interaction was observed. Germination was induced at lower pressure and was faster in milk than in distilled water, but complete germination was not reached. The optimum germination obtained with experimental data was 5.0 log cfu/mL in distilled water and 5.2 log cfu/mL in milk from 5.7 log cfu/mL of spores initially present in the suspension. This study shows the potential of using high hydrostatic pressure to induce the germination of B. sporothermodurans spores in milk before a heat treatment.     

Spatial Variation of Convective Heat Transfer Coefficient in Air Impingement Applications

ABSTRACT Spatial variation of heat transfer is an important factor in air impingement systems. Temperature data were obtained when a jet at room temperature impinged on a flat object initially at −50 °C to estimate heat transfer under freeze-thaw conditions. Single and double circular jets and slot jets were examined. Temperature data were fit into empirical relationships for predicting heat transfer coefficients and their spatial variation for conditions common in impingement freeze-thaw applications. For processing conditions involving cooling, the impingement surface was initially heated to a temperature of 70 °C and allowed to cool when subjected to impingement with room temperature air.     

THERMAL TRANSPORT IN A MULTIPLE JET IMPINGEMENT OVEN

Three‐dimensional numerical simulation of flow field and heat transfer in a jet impingement oven with multiple jets was carried out. Distribution of local heat transfer coefficient on a model cookie in the oven cavity was obtained from the predicted flow and temperature fields, and compared with the experimentally measured values. Effects of air temperature (400, 450K) and air velocity (2.5, 5, 10 m/s), on the surface heat transfer coefficient were studied. Numerical predictions showed good agreement with the experimental results. It was found that heat transfer coefficient was a strong function of air velocity while air temperature had no effect on the heat transfer coefficient. Local heat transfer coefficient values ranged between 11 and 66 W/m²K whereas average heat transfer coefficient values ranged between 24 and 42 W/m²K. Results also showed that because of the presence of the suction fan in the oven, flow field near the model cookie surface was quite different from that for a jet impinging on a flat surface.     

Drying Kinetics of Curcuma longa Rhizomes

ABSTRACT: Modeling drying kinetics is very useful for optimization purposes. Hot air drying kinetics were carried out in monolayer at different temperatures (60°C, 70°C, 80°C, 90°C, and 100°C) and for different sample types (peeled and unpeeled rhizomes of different sizes). Mathematical models based on Fick's law were used to describe water removal, considering different boundary conditions and geometries. Effective moisture diffusivities identified from modeling presented an Arrhenius-type relationship. An additional mass transfer resistance was identified as due mainly to the peridermis layer (peridermial resistance). The accuracy of the model assuming peridermial resistance only in the radial direction and solved using the finite differences method was illustrated, and the mass transfer coefficient was identified (k = 9.7 × 10^-5 kg water/m²/s). Keywords: Curcuma longa , drying, modeling, peridermial resistance     

Storage conditions affect quality of noodles with added soy flour and sweet potato

Summary Noodles were prepared from a formulation in which a portion of the flour was replaced with 10% defatted soy flour and sweet potato as 10% flour or 15% puree. Dried noodles were packaged in plastic bags under partial vacuum or air and stored at 4.4 °C or 22–30 °C for 6 months. Colour, β-carotene and sensory characteristics were analyzed at 2-month intervals. Packaging atmosphere had minor effects on colour. Stored noodles became lighter and yellower, and β-carotene decreased, with all changes being greater at 22–30 °C. Storage conditions influenced acceptability scores minimally. Noodles were stored successfully under air with greater quality retention with 4.4 °C storage.     

Thin-layer drying behaviour of sludge of olive oil extraction

Drying characteristics of sludge were examined for average moisture content from 2 to approximately 0.7–0.08 kg water/kg dry matter using hot air of the range of 20–40–80 °C and simulating the interval that can be provided by an air solar heater and by air velocities of 1 m/s at a laboratory scale dryer. Different mathematical models were used for the simulation of the sludge drying curves, such as Lewis, Page, Modified Page, Henderson and Pabis, Wang and Singh, Logarithmic, Two term, Two Term exponential, Modified Henderson and Pabis, Midilli, Approximation of diffusion, Verma et al. and Simplified Fick’s diffusion models. The performance of these models was investigated by comparing four statistical parameters: the square of the coefficient of determination (r²), reduced chi-square (χ²), root mean square error (RMSE) and sum of residuals between the observed and predicted moisture ratio. The Midilli model represented the drying characteristics better than the others. The effective diffusivity coefficient of moisture transfer varied from 2.224 × 10⁻¹⁰ to 6.993 × 10⁻¹⁰ m²/s over the temperature range. The temperature dependence of the effective diffusivity coefficient was expressed by Arrhenius type relationship. The activation energy for the moisture diffusion was found to be 15.77 kJ/mol.     

HEAT TRANSFER COEFFICIENT FOR COOKIE SHAPED OBJECTS IN A HOT AIR JET IMPINGEMENT OVEN

Correlations for average heat transfer coefficient for cookie shaped objects in a hot air jet impingement oven were obtained using aluminum cookie models. The study was carried out in a pilot plant scale hot air jet impingement oven. The effects of individual cookie position, presence of surrounding cookies, air velocity, air temperature and rotation of the oven plate on average surface heat transfer coefficient were investigated. The value of the heat transfer coefficient ranged between 100–225 W/m²K and was found to be a strong function of jet air velocity. The impact of surrounding cookies on the heat transfer coefficient was more for smaller cookies, which had larger cookie‐to‐cookie spacing.