Influences of Pretreatments and Drying Process Including Fluidized Bed Puffing on Quality Attributes and Microstructural Changes of Banana Slices

Healthy snacks have received more attention because of their low fat content. Color and texture are important to snack quality. Effects of chemical pretreatment, thickness, blanching, and puffing temperature on quality of banana slices were therefore investigated. Banana slices (2.5 and 3.5 mm thickness) were chemically treated by citric acid and sodium metabisulfite, blanched, and dried at a temperature of 90°C to an intermediate moisture content of 25% db. They were then puffed in a fluidized bed dryer at 160 and 180°C for 2 min and dried again at the same drying temperature as the first drying step. Blanching, puffing temperature, and thickness strongly affected the degree of shrinkage, effective moisture diffusivity, morphology, textural properties such as hardness and crispiness, and color, but the chemical treatment did not affect those qualities. Blanching can improve the product appearance; the color was uniform and shiny throughout the surface and golden yellow. However, the textural attributes of the blanched sample had higher hardness and less crispiness than those of unblanched sample.     

Infrared assisted dry-blanching and hybrid drying of carrot

Infrared (IR) blanching and IR assisted hot air (hybrid) drying of carrot slices were attempted and their performance (processing time, retention of vitamin C and rehydration characteristics) was compared with conventional blanching and drying techniques. Intermittent heating of carrot slices using IR radiation (chamber maintained at 180–240 °C) for 8–15 min resulted in desired level of enzyme inactivation. The time required for blanching of carrot slices (10 mm thick) using hot water, steam and IR radiation was 5, 3 and 15 min, respectively. Retention of water soluble vitamin C was higher (62%) in IR blanched carrot as compared to water (43%) and steam (49%) blanching. IR blanching reduced the moisture content by 13–23% (absolute). IR blanched samples dried by hybrid mode took ～45% lesser time compared to water blanched–hot air dried samples. Higher rehydration moisture of dried samples indicated the retention of cell structure during IR blanching. Vitamin C retention was ～39% higher in IR blanched–hybrid dried slices compared to water blanched–hot air dried. The study shows the potential application of dry-blanching and IR assisted hybrid drying in food processing for improving product quality.     

Prediction of crude sunflower oil deterioration after seed drying and storage processes

The effects of air-drying temperature and storage time on several characteristics of crude sunflower oil were evaluated in terms of FFA and PV. Long storage affected oil content to a greater extent than air-drying temperature. FFA and PV varied between 0.53 and 1.22% and between 10.7 and 23.3. meq O₂/kg, respectively, when samples of uniform initial moisture content (approximately 28%) were dried at various temperatures between 25 and 90°C to approximately 7% moisture content, stored for 8 mon, and then analyzed. Both oil quality characteristics increased exponentially with air-drying temperature (T) and linearly with storage time (t). Mathematical functions of the form A·exp(B·T)+C·t (where A, B, and C are parameters adjusted from experimental data) most closely predicted the experimental loss of quality of sunflower oil in terms of FFA and PV with variations in T and t. Statistical analysis showed SE of the estimated parameters of 0.08 and 1.19 and coefficients of determination, R ², of 0.922 and 0.939 for FFA and PV, respectively, which were significant at 95% confidence. High-oleic seeds from a similar experiment were used to validate the proposed equation. The results of applying the mathematical function proposed above showed a reasonable ability to predict the experimental values with SE of 0.037 and 0.808 and R ² of 0.983 and 0.972 for FFA and PV, respectively, which were significant at 95% confidence. Plots of residuals showed random distribution. The results obtained suggested that the equation proposed could be used as a quality-loss model in sunflower drying simulations.     

Drying Behavior of Carrots Dried in a Spout–Fluidized Bed Dryer

The effect of water blanching treatment and the inlet air temperature on drying kinetics as well as the quality attributes of carrot cubes dried in a spout–fluidized bed dryer at 60, 70, 80, and 90°C were analyzed. The material shrinkage and the rehydration potential were calculated to assess the changes in quality of dried carrots. It was found that the value of the air velocity during the drying of carrot cubes in a spout–fluidized bed dryer should be related to the moisture content of the carrot particles. A high value of air velocity at the beginning of the drying cycle and a lower value for the later stages were also required. The linear equation was correlated to the data of shrinkage of raw and blanched carrots. Blanching significantly influenced the coefficients in the shrinkage model derived for drying of carrot cubes in a spout–fluidized bed dryer, while drying temperature did not influence the shrinkage of carrot particles. The intensity of heat and mass transfer during spout–fluidized drying of carrot cubes was dependent on the drying temperature. A correlation was developed to calculate the values of effective moisture diffusivity of dried carrot cubes as a function of the moisture content and temperature of the material. It was observed that for any given time of rehydration, both the moisture content and the rehydration ratio calculated for samples dried at 60°C were higher than for samples dried at temperatures of 60, 70, 80, and 90°C.     

Microwave vacuum drying of lotus seeds: Effect of a single-stage tempering treatment on drying characteristics,moisture distribution,and product quality

This study evaluated the effects of a single-stage tempering treatment during microwave vacuum drying (MVD) on drying characteristics and quality of lotus (Nelumbo nucifera Gaertn.) seeds using two parameters: intermediate moisture content (IMC) and tempering temperature (4 and 25°C). Magnetic resonance imaging (MRI) was used to examine moisture migration and distribution in individual lotus seed during tempering. Results from MRI showed tempering could reduce the moisture gradient in lotus seeds during MVD. The tempering treatments led to increased moisture diffusivity (3.96–43.56%) and a shortened drying time (6.25–31.25%) when compared with continuous MVD. Furthermore, tempered samples exhibited a greater rehydration capacity, a limited overall color change, and increased amounts of taste-active amino acids when compared with nontempered lotus seeds. High IMC improved rehydration ratios of dried samples. Low tempering temperature provided favorable free amino acid content and desirable product color.     

Usage of solar-assisted spouted bed drier in drying of pea

The main objective of this study is to evaluate the effects of solar-assisted spouted bed and open sun drying on the drying rate and quality parameters of pea. Color, shrinkage, bulk and apparent densities, internal and bulk porosities, rehydration capacity and microstructure were the quality parameters investigated in dried product.Drying rate for solar-assisted spouted bed was about 3.5 times of drying rate for open sun drying. Air temperature changed between 20 °C and 27.4 °C during open sun drying while temperature of air at the inlet of solar-assisted spouted bed dryer varied between 35.3 °C and 65.5 °C during the experiments. Effective diffusivities were found to be 0.64 × 10^?10 and 3.27 × 10^?10 m²/s for open sun and solar-assisted spouted bed drying of pea, respectively. In color analysis, it was observed that a* value increased while b* value decreased for both drying methods. Bulk density and apparent density of peas dried under open sun was higher than that in solar-assisted spouted bed drier. In both drying methods, internal and bulk porosities decreased. Shrinkage was more for open sun dried samples. Rehydration capacity for solar-assisted spouted bed dried sample was higher than the one for open sun dried.     

Mathematical Modeling of Drying Characteristics of Indian Mackerel (Rastrilliger kangurta) in Solar-Biomass Hybrid Cabinet Dryer

Eight trials were conducted for drying mackerel by a solar biomass hybrid cabinet dryer (S-BHCD) and open sun drying (OSD) at air temperatures of 32.39–57.69°C, relative humidity 23.9–85.8%, and air flow rate of 0.20–0.60 m/s. The solar radiation ranged between 287 and 898 W/m² during the time of experimentation. At nighttime, drying was carried out by combusting biomass. The initial moisture content of the processed mackerel was 72.50±0.44% (w.b.) and was reduced to the final moisture content of 16.67±0.52% (w.b.) in S-BHCD and 16.92±0.54% (w.b.) in OSD. Eleven drying models were used and the coefficients of determination (R ²) and constants were evaluated by nonlinear regression to estimate the drying curves of dried mackerels. The Midilli model was found to more satisfactorily describe the drying process of mackerel in S-BHCD with R ² of 0.9999, χ² of 0.0000374, and RMSE of 0.0057. In the OSD, a two-term drying model satisfactorily described the drying process with R ² of 0.9996, χ² of 0.0000519, and RMSE of 0.0072. The variation of Free Fatty acid (FFA), Peroxide value (PV), Thiobarbituric acid (TBA), Total volatile bases nitrogen (TVB-N), Trimethylamine nitrogen (TMA-N), and histamine contents of dried mackerel by using S-BHCD showed very high corresponding coefficients of determination, where all R ² were greater than 0.90, except TBA value. Bacterial count and mold growth were decreased significantly (P < 0.05). There was no discoloration of the product during 4 months of storage. Contour plots of S-BHCD and OSD dried mackerel also showed that for all sensory attributes examined, panelists preferred fish dried with S-BHCD. The organoleptic analysis showed that the S-BHCD drying methods have a highly significant effect (P < 0.01) on texture and overall acceptability. Biochemical, microbial analysis, and sensory evaluation showed that the product was in prime acceptable form for 4 months of storage at ambient temperature.     

Effects of acid pretreatments on some physicochemical properties of carrot undergoing hot air drying

Carrot is one of the important root crops cultivated worldwide. In many cases, carrot must be dried prior to its use. Although hot air drying is one of the most common methods for drying carrots, it is well known that hot air drying leads to much quality degradation of a dried product. To alleviate the adverse effect of hot air drying many pretreatment methods have been proposed. In this study, the effects of pretreatments with citric acid, which is used as an anti-darkening agent and a texture-modifier, were investigated. Carrots were soaked in citric acid to pH of either 4 or 5 or blanched in citric acid to pH of either 4 or 5 prior to hot air drying. Untreated carrots, carrots soaked in water and carrots blanched in water were used as control samples. The effects of pretreatments, in combination with hot air drying at 70, 80 and 90 °C, on selected physicochemical properties of dried carrots, namely, color, shrinkage, rehydration ability, β-carotene content and cis–trans isomerization of β-carotene, were evaluated. It was noted that carrots, which were soaked and blanched in citric acid, were redder than the untreated sample. Although shrinkage of pretreated carrots was higher, the rehydration ability of the pretreated carrots was higher than that of the untreated sample. The β-carotene content of carrots with no pretreatment decreased continuously, whereas the contents of β-carotene in citric acid soaked and blanched carrots tended to be unchanged. However, isomerization of β-carotene in all samples was not significantly different.     

Effects of drying methods and enzyme aided on the fatty acid profiles and lipid oxidation of rice by-products

We investigated the influence of hot air drying, far infrared radiation (FIR), and cellulase aided on the fatty acid composition and primary lipid oxidation of rice bran, rice husk, and ground rice husk. The lipid content was significantly reduced in the sample dried by hot air and FIR but remained unchanged in the cellulase-aided rice bran and husk. We found that oleic acid (18:1n ? 7) and linoleic acid (18:2n ? 6) increased in hot air- and FIR-dried rice bran. On the other hand, PUFA content was significantly reduced in the samples dried by hot air and FIR but remained unchanged in the cellulase-aided rice bran and husk. Cellulase aided gave significantly higher concentrations of SFA, MUFA, and PUFA in all samples than did hot air and FIR drying. However, the rice by-products dried with hot air and FIR had the lowest PV and TBA values during 30 days of storage. Our findings provide useful information for the pretreatment of rice by-products; consequently, more utilization of rice by-products will be extended for uses such as oil production.     

Effect of advanced chilling methods on lipid damage during sardine (Sardina pilchardus) storage

Slurry ice is a biphasic system consisting of small spherical ice crystals surrounded by seawater at subzero temperature. Its effect on lipid damage (hydrolysis and oxidation) was evaluated during the chilled storage of a fatty fish species, sardine (Sardina pilchardus). Slurry ice treatment was checked alone and in combination with ozone and compared to traditional flake icing during a 22‐day storage. Different lipid damage indices (free fatty acids, FFA; peroxide value, PV; thiobarbituric acid index, TBA‐i; fluorescent compounds, FR) were checked and compared to sensory assessment and nucleotide degradation (K value). According to lipid hydrolysis (FFA) and oxidation (PV and FR) developments, slurry ice showed an inhibitory effect (p <0.05) on lipid damage during storage, as well as an inhibition of nucleotide autolytic degradation. Ozonised slurry ice did not provide differences (p >0.05) from slurry ice alone when considering lipid hydrolysis, nucleotide degradation and some lipid oxidation indices (PV and FR), although a higher (p <0.05) TBA‐i was observed at day 22 of storage when compared to flake ice and slurry ice treatments. However, a lower (p <0.05) fluorescence development was observed for fish treated under ozonised slurry ice when compared to traditionally iced fish. Sensory assessment showed a higher shelf life for fish samples treated under ozonised slurry ice than for their counterparts under slurry ice (15 d versus 12 d), while flake icing led to a far shorter shelf life (5 d). According to sensory and biochemical (lipid matter and nucleotide) analysis, slurry ice has proved to be a promising technology for damage inhibition and quality retention in a fatty fish species such as sardine. Ozonised slurry ice was also shown to be useful, since a longer shelf life was obtained in the present experiment and a pro‐oxidant effect of ozone on sardine lipids was not proved.     

Effect of Microwave-Vacuum Drying on the Carotenoids Retention of Carrot Slices and Chlorophyll Retention of Chinese Chive Leaves

Microwave-vacuum drying, and combined microwave-vacuum with air or vacuum drying were investigated as potential methods for drying green and high-carotenoid vegetables of Chinese chive leaves and carrot slices. The samples were dried by microwave-vacuum until the moisture content reached about 20% (wet basis), and then by conventional air drying at the temperature of 45-50°C or conventional vacuum drying at the temperature of 55-60°C or by continued microwave-vacuum drying at lower power level to final moisture content about 6% (wet basis). The carotenoid retention of carrot slices and chlorophyll retention of Chinese chive leaves, dried by these methods, was evaluated and compared with those dried by freeze-drying and conventional hot-air drying. The comparison showed that the carotenoid retention of carrot slices and chlorophyll retention of chive leaves, dried by the current methods, was very close to or even as much as those dried by freeze-drying and much better than those dried by conventional hot-air. Blanching was not necessary when using microwave-vacuum drying or combined microwave-vacuum with conventional hot-air drying or vacuum drying, because the activity of enzymes which were responsible for the degradation of color was greatly reduced with extremely rapid decreasing of moisture, and because oxygen was absent in microwave-vacuum drying.     

Microbial and biochemical analysis of dried fish and comparative study using different drying methods

In the present study, certain quality parameters of raw and traditionally sun-dried (TSD) Bombay duck samples are compared with dried fish samples obtained from hot air dryer (HAD), freeze dryer, and a newly developed and patented solar conduction dryer (SCD). The parameters analyzed are total viable count, total fungal count, total volatile nitrogen, and trimethylamine (TMA) content and color. It is found that the experimentally dried fish have better microbial and biochemical quality as compared to TSD fish. This study addresses the issue of unhygienic open sun drying and handling of dried products and the need to adopt use of dryers based on the recently developed appropriate drying technology such as SCD which is expected to be transformed into sustainable technology.     

Quality evaluation of pineapple fruit during drying process

Pineapple (Anana comosus) slices were dried by hot-air convective drying technique at fixed temperature (45, 60 and 75 °C) and constant air velocity of 1.5 m/s. The effect of drying conditions (drying time and air temperature) on the pineapple quality was evaluated. The quality of dehydrated pineapple was analyzed by color and texture changes, l-ascorbic acid loss and the ability of water uptake during rehydration procedure. Water uptake during rehydration was described by Page model. Statistical analysis of data revealed not significant difference (p > 0.05) among color and mechanical characteristics of pineapple samples dried at different drying temperatures to preset moisture content. Pineapple samples dried at 45 °C had better rehydration ability and more l-ascorbic acid retention than those obtained by air drying 75 °C. Hence, 45 °C drying temperature was best condition for pineapple quality preservation.     

Effects of three conventional drying methods on the lipid oxidation,fatty acids composition,and antioxidant activities of walnut (Juglans regia L.)

Three walnut (Juglans regia L.) drying methods (sun drying, direct oven drying, and intermittent oven drying) were employed, and the consequent changes in lipid oxidation attributes, such as acid value (AV), peroxide value (POV), saponification value (SV), fatty acid composition, and antioxidant activity [including reducing power, superoxide anion scavenging activity, 1,1-diphenyl-2-picrylhydrazyl free radical scavenging activity (DPPH), lipoxygenase (LOX) activity, total phenols content (TPC), and total flavonoids content (TFC)] were investigated in this study. Sun drying resulted in the highest AV, POV, and SV, followed by direct oven drying and intermittent oven drying. Antioxidant activities and related compounds, TPC and TFC, were initially increased and then declined during drying, and a significant correlation was found between antioxidant activity and TPC and TFC. The LOX activities of all samples showed an increasing trend, although those of the sun-dried samples were the lowest. The walnuts dried with the intermittent oven drying method contained more linoleic acid than those dried by direct oven drying. Overall, intermittent oven drying appears to be a promising strategy for fresh walnut drying.     

Red pepper (Capsicum annuum L.) drying: Effects of different drying methods on drying kinetics,physicochemical properties,antioxidant capacity,and microstructure

Results of an experimental study are presented and discussed for pulsed vacuum drying (PVD), infrared-assisted hot air-drying (IR-HAD), and hot air-drying (HAD) on drying kinetics, physicochemical properties (surface color, nonenzyme browning index, red pigments, rehydration ratio, water holding capacity, and ascorbic acid), antioxidant capacity (ferric reducing antioxidant power and 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity), and microstructure of red pepper. As expected, the drying time decreased with an increase in drying air temperature, IR-HAD needed the shortest drying time, followed by HAD and PVD. The effective moisture diffusivity (D_eff) of red pepper under PVD, HAD, and IR-HAD was computed to be in the range 1.33–5.83?×?10^?10, 1.38–6.87?×?10^?10, and 1.75–8.97?×?10^?10 m²/s, respectively. PVD provided superior physicochemical properties of dried red pepper compared to samples dried by HAD and IR-HAD. In detail, PVD yielded higher rehydration ratio, water holding capacity, red pigment and ascorbic acid content, brighter color, lower nonenzyme browning index, and comparable antioxidant capacity compared to samples dried by HAD and IR-HAD at the same drying temperature. Furthermore, PVD promoted the formation of a more porous structure, while HAD and IR-HAD yielded less porous structure. The current findings indicate that PVD drying has the potential to produce high-quality dried red pepper on commercial scale.     

Drying Kinetics,Texture, Color,and Determination of Effective Diffusivities During Sun Drying of Chempedak

Sun drying of chempedak (Artocarpus integer) was carried out on different sample sizes to investigate the effects on product quality. Fick's second law model was used to determine the effective diffusivities of sun–dried chempedak slabs based on the drying rate versus moisture content plots. In addition, texture degradation and total color changes were investigated. The texture and color changes of dried chempedak were relatively significant (p < 0.05) compared to fresh chempedak. There was an increase in dried fruit hardness and chewiness but a decrease in springiness and cohesiveness during drying.     

Physicochemical Properties of Red Salmon Oil (<Emphasis Type="Italic">Oncorhynchus nerka</Emphasis>) and Microencapsulated Red Salmon Oil Added to Baby Food

Unpurified red salmon oil (UPSO) was processed to obtain purified salmon oil (PSO) by chitosan adsorption. Both unpurified and purified oils were evaluated for peroxide value (PV), free fatty acids (FFA), fatty acid methyl esters (FAME), moisture, and color. An emulsion system containing PSO (EPSO) was prepared; the system was analyzed for color, rheological properties and microstructure before spray drying to produce microencapsulated PSO (MPSO). MPSO was analyzed for moisture, water activity, bulk density, color and FAME composition. PSO or MPSO was added to a commercial baby-food product (CB) and all baby-food samples were compared for PV, FFAs, FAME, and color. Experiments were completed in triplicate and data statistically analyzed (α = 0.05). PSO had higher percentages of total omega-3, total monounsaturated DHA, and EPA than MPSO. EPSO exhibited viscoelastic characteristic and the droplet size of EPSO was 1–9 μm. Total omega-3 and total monounsaturated contents of the MPSO were lower than PSO. All baby-food samples with added fish oils had similar color. DHA and EPA contents of baby food were increased over three fold by the addition of PSO and/or MPSO. MPSO can be added to CB resulting in increasing total percent omega-3 fatty acids while maintaining desirable attributes of the CB.     

Dehydration of asparagus cookies by combined vacuum infrared radiation and pulse-spouted microwave vacuum drying

ABSTRACT

The restructured cookies were made from old stalks of asparagus (Asparagus officinalis). Combination of vacuum infrared radiation drying and pulse-spouted microwave vacuum drying (VIRD–PSMVD) was studied as a potential mean for dehydration of restructured cookies. The samples were first dried by VIRD and then by PSMVD to final moisture content less than 6%. Expansion ratio, texture, color, flavor, and other attributes of samples dried by this method were evaluated and compared with those dried by PSMVD and VIRD. Results showed that the samples dried by VIRD–PSMVD showed higher overall acceptability, crisper texture, and higher expansion ratio.     

Study of drying kinetics of salmon processing by-products at different temperatures and the quality of extracted fish oil

Samples of salmon processing by-products were minced, mixed, and partially dried to moisture content of 90?±?5% (dry basis), at two different temperatures 60 and 100°C (using hot air-drying and oven-drying, respectively). Theoretical and semitheoretical drying models were used for modeling of the drying kinetics of salmon by-products mix, where Page model and logarithmic models were observed as the best models presenting the drying kinetics of salmon by-products at 60 and 100°C, respectively. Salmon by-product oil was extracted from the partially dried by-product through centrifugation and was compared with enzymatically extracted (enzymatic extraction method was considered as the control method) salmon oil, in terms of fatty acid profile of the oils. The oil content obtained through semidried samples and enzymatically treated samples ranged between 16.234 and 18.212?g/100?g of fresh sample, which were not significantly different. The fatty acid composition was similar in all the cases. The fatty acids predominantly observed in the salmon oils included oleic acid, linoleic acid, and palmitic acid. Other fatty acids included palmitoleic acid, stearic acid, vaccenic acid, gondoic acid, and myristic acid. Docosahexaenoic acid and eicosapentaenoic acid contents were between 1 and 2% of the oil extracted in all the cases, and DPA (Docosapentaenoic acid) content was approximately 1%. Hence, partial dehydration at both the temperatures was concluded as a potential processing method for increasing the storability of salmon by-products and obtaining salmon oil with high quality.     

Drying Kinetics of Tomato Slices in Vacuum Assisted Solar and Open Sun Drying Methods

A lab model vacuum-assisted solar dryer was developed to study the drying kinetics of tomato slices (4, 6, and 8 mm thicknesses) compared with open sun drying under the weather conditions of Montreal, Canada. The drying study showed that the time taken for drying of tomato slices of 4, 6, and 8 mm thicknesses from the initial moisture content of 94.0% to the final moisture content of around 11.5 ± 0.5% (w.b.) was 360, 480, and 600 min in vacuum-assisted solar dryer and 450, 600, and 750 min in open sun drying, respectively. During drying, it was observed that the temperature inside the vacuum chamber was increased to 48°C when the maximum ambient temperature was only 30°C. The quality of tomato slices dried under vacuum-assisted solar dryer was of superior quality in terms of color retention and rehydration ratio. The drying kinetics using thin-layer drying models and the influence of weather parameters such as ambient air temperature, relative humidity, solar insolation, and wind velocity on drying of tomato slices were evaluated.