Foam-mat drying of cowpea (<Emphasis Type="Italic">Vigna unguiculata</Emphasis>) using glyceryl monostearate and egg albumin as foaming agents

Foam-mat drying of cowpea using glyceryl monostearate (GMS) and egg albumin (EG) as foaming agents was investigated. GMS and EG were incorporated into cowpea paste (22%, 25% and 28% total solids) at 2.5, 5.0, 7.5, 10.0, 12.5 and 15% (w/w), and whipped for 3, 6, 9, 12, 15, 18 and 21 min, maintaining 15, 25 and 35 °C foaming temperatures. Foam density was measured and expressed in g/cm³. Cowpea foams were dried at 60 °C (Twb, wet bulb temperature 35 °C) for 48 min. Sensory attributes of akara produced from fresh and reconstituted pastes were evaluated.Generally, foam density decreased with increased concentrations of GMS and EG in cowpea paste. Foam density decreased with decrease in total solids of cowpea paste. Minimum foam densities were obtained in cowpea foams with GMS and EG after 9 and 21 min of whipping, respectively. EG-stabilized foams were unstable for drying. Sensory evaluation showed no significant difference (P>0.05, 0.01) in the quality attributes of akara produced from fresh and reconstituted GMS-stabilized cowpea powders.     

Effects of Cultivar and Drying Method on Color,Pasting and Sensory Attributes of Instant Yam (<Emphasis Type="BoldItalic">Dioscorea rotundata</Emphasis>) Flours

Effect of cultivar (Efuru and Abuja) and drying method (cabinet and foam mat) on color, pasting, and sensory properties of instant pounded yam flours was investigated. Color (L*, a*, b*) values of fresh and dried flour samples were measured, and deltachroma (∆C), color difference (∆E), and hue angle were calculated. Pasting properties of flour and sensory attributes of fresh and reconstituted flour were determined. Foam density of yam pastes decreased from 0.97 g/cm³ to between 0.362–0.538 and 0.308–507 g/cm³ for cultivars Abuja and Efuru, respectively. Foam-mat dried flour showed higher L*, ΔC, ΔE, and hue angle but lower a* and b* values. Peak viscosities of cabinet and foam-mat dried Abuja and Efuru were 217, 304, 377.42, and 316.50 RVU, respectively. Sensory attributes of reconstituted foam-mat dried Abuja and fresh pounded yam were not significantly different (p > 0.05). However, fresh pounded yam (8.5–8.9) and reconstituted foam-mat dried flour (7.4–8.5) samples were significantly different (p > 0.05) from the cabinet-dried (6.9–7.9) and commercial samples (7.2–7.8).     

Effect of Processing Methods on Physical,Chemical, Rheological,and Sensory Properties of Okra (<Emphasis Type="Italic">Abelmoschus esculentus</Emphasis>)

Effects of freezing/thawing, sun drying, solar drying, and foam-mat drying on physical, chemical, rheological, and sensory attributes of okra were investigated. Average poured bulk and tapped bulk densities of sun-dried, solar-dried, and foam-mat-dried okra were 800 and 950, 715 and 765, 355 and 367 kg/m³, respectively. Minimum and maximum porosity of sun-dried, solar-dried, and foam-mat dried okra were 55.70% and 62.60%, 50.06% and 53.30%, 60.90% and 62.87%, respectively. Sun-dried and solar-dried okra showed higher L*, a*, and chroma values than frozen/thawed and foam-mat-dried okra. Within a temperature range of 80–40 °C, viscosity of fresh, frozen/thawed, foam-mat-dried, solar-dried, and sun-dried okra were 0.055–0.080, 0.055–0.075, 0.050–0.073, 0.005–0.065, and 0.005–0.022 Nsm⁻², respectively. Sensory evaluation showed no significant difference (p < 0.05) between fresh, frozen/thawed, and foam-mat dried okra in color, aroma, and overall acceptability. Sun-dried and solar-dried okra were significantly poorer (p < 0.05) in color, aroma, taste, and overall acceptability.     

Foam-mat drying of starfruit (Averrhoa carambola L.) purée. Stability and air drying characteristics

Foams were prepared from starfruit (Averrhoa carambola L.) purée by adding various concentrations of methocel. Overrun and density of the foams from various concentrations of methocel were compared. Relative stability of the foam was determined by comparing amounts of juice separated from foam at 70°C. Drying rates at two drying temperatures (70 and 90°C) were also compared. Quality of the dry and reconstituted powder was evaluated with simple sensory evaluation and Hunterlab instrument. Overrun and stability of foams increased with increasing methocel concentration until maximum value was obtained at a methocel concentration of 0.4% w/w. Falling rate was observed for foam dried at both temperatures. Drying time could be shortened by as much as 30 min when drying temperature was increased from 70 to 90°C. However, obvious colour and flavour changes were observed in the product dried at 90°C. This study has indicated that, under the experimental conditions employed, reasonably good powder characteristics can be obtained.     

Optimization of Process Parameters for Foaming of Bael (Aegle marmelos L.) Fruit Pulp

Foam expansion and foam stability of the bael (Aegle marmelos L.) fruit pulp foam was studied. Foams were prepared from various pulp concentrations (PC) by adding different concentration of glycerol monostearate (GMS) and methyl cellulose (MC) at different whipping time (WT). Response surface methodology was used to predict the foam stability and expansion. Thirty experiments were carried out using a central composite rotatable design with four independent variables (GMS, MC, PC, and WT). Second-order polynomial equations were developed after removing insignificant terms for predicting foam expansion (R ² = 0.85) and stability (R ² = 0.95). The optimum conditions achieved after the numerical and graphical optimization for maximum foam expansion and stability was: GMS (3.10 g/100 g pulp), MC (0.32 g/100 g pulp), PC (13.2°Bx), and WT (2 min). The desirability of 0.712 was achieved at this optimum point. The predicted values of foam density and foam drainage volume were 0.658 g cm⁻³ and 1.75 mL, respectively, at optimum parameters while the experimental values were 0.635 ± 0.02 g cm⁻³ and 1.75 ± 0.12 mL, respectively.     

Quality Evaluation of an Ohmically Cooked Ham Product

Selected parameters (cooking loss, instrumental colour and texture and sensory quality) of a brine-injected pork muscle cooked by a novel and rapid ohmic cooking protocol were examined and compared with those obtained in conventionally cooked samples. Ohmic samples were cooked using either a low-temperature long-time (LTLT) protocol (2 min equilibration, 5 min ohmic heating to 70 °C, 8 min holding) or a high-temperature short-time (HTST) procedure (2 min equilibration, 6 min ohmic heating to 95 °C) performed within a hot air cabinet set at 80 °C (LTLT) and 100 °C (HTST). Conventional cooking (steam oven at 80 °C for 120 min) was conducted to a core temperature of 70 °C. The LTLT treatment gave a much lower cooking loss value (4–5% lower, p < 0.05) than the other treatments, though the full magnitude of this difference was not completely reflected in the proximate composition of the cooked products. Ohmically cooked ham showed a significantly (p < 0.05) lighter surface colour with Hunter L values of 65.3 (LTLT) and 63.5 (HTST) relative to the control (61.4). Texture profile analysis (TPA) indicated a significant difference (p < 0.05) in hardness (N) especially between the HTST surface (82.1 N) and the conventional centre (58.8 N). Although the ohmic cooking protocols yielded products with quite acceptable eating qualities, sensory evaluation found the overall quality of the conventionally cooked ham to be significantly (p < 0.05) superior, indicating that further optimisation of the ohmic cooking protocols would be required prior to any commercial adoption.     

An Approach for Monitoring the Moisture Content Changes of Drying Banana Slices with Laser Light Backscattering Imaging

Moisture content is an important quality attribute that directly influences storability of fruits and vegetables. The main goal of the present work was to test laser light backscattering imaging technique as a monitoring tool during drying of banana (Musa × cavendishii L.) slices. Laser diode emitting at 670 nm was used as the light source, whereas a charge-coupled device camera served as detector. The photon migration into the tissue was recorded as the average profile of the intensity gradient and expressed by two parameters, the size of the total illuminated area (square centimeters) on the surface and the radius (centimeters) of this area. The two attributes correlated with each other (r = 0.97–0.98). Backscattering images of slices were acquired each hour during the drying process at three different temperatures: 53, 58, and 63 °C. The two parameters of the intensity profile responded sensitively to changing moisture content. Significant relationship was found between changes in backscattering area and moisture content, especially at lower temperatures (r = 0.76, T = 53 °C), when almost no tissue browning occurred. At higher temperatures, correlations were observed between the parameters extracted by image processing and a* standard color index, especially at increased drying temperature due to the browning of the tissue.     

Physicochemical and Enzymatic Properties of Five Kiwifruit Cultivars during Cold Storage

Samples of Abbot, Alison, Bruno, Monty, and Hayward cultivars of kiwifruit (Actinidia deliciosa) were obtained from the Iran Research Center of Citrus (Tonekabon, located in north of Iran) and their physicochemical properties were studied during cold storage (at T = 1 ± 1 °C, RH = 80 ± 5%) at 0-, 9-, and 18-week intervals. The mean chemical composition of the fruits were as follows: ash = 0.66–0.96%, moisture = 75.2–84.7%, starch = 0.3–7.0%, and ascorbic acid = 54.8–261.0; K = 125.0–372.0 mg 100 g⁻¹ fresh weight, Mg = 18.0–32.0 mg 100 g⁻¹ fresh weight, Na = 1.4–3.1 mg 100 g⁻¹ fresh weight, Fe = 0.17–0.52 mg 100 g⁻¹ fresh weight, Cu = 0.04–0.24 mg 100 g⁻¹ fresh weight, Zn = 0.16–0.49 mg 100 g⁻¹ fresh weight, Mn = 0.04–0.10 mg 100 g⁻¹ fresh weight, and P = 25.2–49.3 mg 100 g⁻¹ fresh weight; glucose = 0.7–2.39%, fructose = 1.20–3.13%, and sucrose = 0.0–5.8%. At the same time, the values of the parameters °Brix = 6.5–14.8% and acidity = 1.8–2.5% of the studied cultivars (mutual effects of cultivar and storage time) were investigated. The increase in peroxidase (POX = 0.0–6.65 U ml⁻¹) and the decrease in pectinesterase (PE; poor activity to 0) activities were also determined. The statistical analysis showed that the Bruno cultivar had the highest content of ascorbic acid (115.0–261.0 mg 100 g⁻¹ fresh weight), which is an important compound in fruits during storage, while Hayward had the best overall quality particularly with regards to its resistance to softening. This study confirms that long-term cold storage at 1 ± 1 °C and 80 ± 5% RH is suitable for maintaining the highest quality of Iranian grown cultivars of kiwifruit.     

Effect of Air-Drying Conditions on Physico-chemical Properties of Osmotically Pre-treated Pomegranate Seeds

The drying of pomegranate seeds was investigated at 40 °C, 50 °C and 60 °C with air velocity of 2 m/s. Prior to drying, seeds were osmodehydrated in 55 °Brix sucrose solution for 20 min at 50 °C. The drying kinetics and the effects of osmotic dehydration (OD) and air-drying temperature on antioxidant capacity, total phenolics, colour and texture were determined. Analysis of variance revealed that OD and air-drying temperature have a significant influence on the quality of seeds. Both anthocyanin and total phenolic contents decreased when air-drying temperature increased. The radical diphenylpicril-hydrazyl activity showed the lowest antioxidant activity at 60 °C. Both chromatic parameters (L*, C* and h°) and browning index were affected by drying temperatures, which contributed to the discolouring of seeds. The final product has 22%, 20% and 16% of moisture; 0.630, 0.478 and 0.414 of a _w; 151, 141 and 134 mg gallic acid equivalent/100 g fresh matter (FM) of total phenolics; 40, 24, 20 mg/100 g FM of anthocyanins and 46%, 39% and 31% of antioxidant activity, for drying temperatures of 40 °C, 50 °C and 60 °C, respectively. In view of these results, the temperature of 40 °C is recommended as it has the lowest impact on the quality parameters of the seeds. Differential scanning calorimetry data provided complementary information on the mobility changes of water during drying. Glass transition temperature (Tg′) depends on moisture content and as consequence, on drying conditions. In fact, Tg′ of seeds dried at 60 °C (Tg′ = −21 °C) was higher than those dried at 50 °C (Tg′ = −28 °C) or 40 °C (Tg′ = −31 °C) and osmodehydrated seeds (Tg′ = −34 °C). During OD and drying process, the texture of seeds changed. The thickness of seeds shrank by 55% at 60 °C.     

Effects of foaming agents and foam density on drying characteristics and textural property of banana foams

The technique of foaming has proved effective in creating a porous structure, which is an important requirement for crisp food. Foam density and the type of foaming agent indeed play a key role in determining the drying kinetics and textural property of the foamed food. The influences of the foam density and the types of foaming agents on the moisture diffusivity as well as the quality in terms of microstructure, texture and volatile losses of banana foams were therefore investigated. Three foaming agents, i.e., fresh egg albumen (EA), soy protein isolate (SPI) and whey protein concentrate (WPC) were used. The experimental results showed that WPC banana foam could retain more open structure during drying. This morphology provided less shrinkage and led to higher values of the effective diffusivity as compared with that of SPI and EA banana foams. In terms of the textural properties, WPC and EA banana foams were spongy and less crisp than SPI banana foam. Samples with lower foam densities exhibited higher values of the effective diffusivity, smaller hardness and lower crispness than those with higher foam densities. The losses of volatile substances were substantial during all processing steps, but the major losses were during the foaming step.     

Effect of Blanching and Drying Temperature on Polyphenolic Compound Stability and Antioxidant Capacity of Apple Pomace

The effects of blanching and drying treatments on stability, physical properties, and antioxidant activity of apple pomace polyphenols were evaluated. Blanched and unblanched apples were extracted, and the pomace was dried in a cabinet dryer at a speed of 3 m/s at 50 °C, 60 °C, 70 °C, and 80 °C. The color, total phenolics, flavonoids, individual polyphenolic compounds, anthocyanins, and total antioxidant activity were analyzed. The blanching process caused a major retention in color, total polyphenolic content, and total flavonoid content for fresh apple pomace when compared with fresh unblanched pomace. Drying of either fresh blanched or fresh unblanched pomace caused a significant reduction (P < 0.05) in total polyphenol and flavonoid content leading to a reduction in the total antioxidant activity. When compared with the unblanched treatment, drying the blanched pomace at 80 °C resulted in a product with significant amounts of total phenolics, flavonoids, and antioxidant activity. The individual phenolic compounds were significantly increased (P < 0.05) in blanched pomace that was not dried when compared with unblanched samples. Drying blanched apple pomace did not cause a significant change in the concentration of individual polyphenolic compounds, but drying unblanched apple pomace caused a reduction in the concentrations of epicatechin and caffeic acid, with an important reduction in p-coumaric acid at temperatures higher than 60 °C. However, the drying process caused a significant reduction in the antioxidant capacity. Therefore, a combination of blanching and drying processes for apple pomace results in a product that maintains antioxidant capacity.     

The Instant Controlled Pressure Drop Process as a New Post-harvesting Treatment of Paddy Rice: Impacts on Drying Kinetics and End Product Attributes

The instant controlled pressure drop (DIC) process was used as a post-harvesting treatment, followed by hot air drying and shade polishing. DIC treatment, which is carried out at P = 0.4–0.6 MPa, has many advantages in terms of processing time (not exceeding 30 s) and drying kinetics (about 3 h instead of 1 day under standard 50 °C hot air flow conditions). Shade polishing gives high quality rice with a whole-grain yield of 68-70% rather than the usual 52-60%. A tasting evaluation was carried out by an international panel and the rice was found to be perfect after a cooking time of 6 min, with an overcooked time of 18 min as against 17 min and 20 min, respectively, for conventional products. The shaded shelf life of the final product is much longer than 18–24 months.     

Freezing, thawing and cooking effects on quality profile assessment of green beans (cv. Win)

Results are presented of the effect of freezing followed by thawing (air and water immersion, both at environmental temperature) and cooking (traditional boiling in a covered pot) on quality profile (in terms of objective texture, colour, chlorophylls and pheophytins and sensory attributes) and structure of green beans (cv. Win). Freezing was carried out at three different rates by forced convection with liquid nitrogen vapour. Kramer shear cell (KSC) and Warner–Bratzler (WB) tests were used for objective assessment of the texture. The highest parameter values occurred in beans frozen at the highest rate and air-thawed at the slowest rate. Also, minimum alteration of the rheological behaviour of cooked beans was achieved by freezing at the highest rate. The best parameter for assessing the texture of frozen green beans after thawing and cooking was the Warner–Bratzler slope (S _WB). Coefficients of softening estimated for S _WB in the thawed beans showed that the texture of the beans frozen at −24 °C was almost four and almost five times softer than that of the beans frozen at −70 °C, for air and water thawing respectively. Frozen and thawed green beans were darker than fresh control, whereas freezing prior to cooking produced lighter-coloured beans than direct cooking. The freezing rate affected colour parameters differently depending on the process that followed. When beans were thawed, increasing the freezing rate produced lighter-coloured beans, whereas when beans were cooked, increasing the rate produced darker-coloured beans. No difference was found in sensory assessments between cooked samples frozen at −24 °C, −35 °C and −70 °C, which probably reflects the panellists' mixed preferences for quickly and slowly frozen samples. Scanning electron microscopy (SEM) revealed different degrees of mechanical damage to tissue structure, which accounted for the rheological behaviour of the beans.     

Viscometric Behavior of Reconstituted Tomato Concentrate

The rheological properties of tomato concentrates produced by hot and cold break have been extensively studied by many authors. Only a few studies, however, focus specifically with the rheology of reconstituted concentrates from tomato powders. In this study, the rheological properties of reconstituted tomato concentrate from lyophilized freeze-dried tomato juice were evaluated using rotational viscometer at temperatures 20 °C, 30 °C, 40 °C, 50 °C, and 60 °C and at concentrations of 9.7%, 12.9%, 20.5%, and 26.8% total soluble solids. Using power law model, both flow behavior index (n) and consistency coefficient (k) were determined. The calculated values of flow behavior index (n) were less than unity (0.03–0.28) at all temperatures and concentrations indicating the shear-thinning characteristic of the concentrate. The effect of temperature and concentration on the consistency coefficient (k) was studied. Positive correlation between k in the range of 1.57 and 38.33 Pa s ⁿ and inverse absolute temperature (1/T) has been shown by Arrhenius model. Additionally, linear correlation between consistency coefficient (k) and concentration (C) was determined. The activation energies were found in the range of 3.63 and 7.36 kJ/mol K depending on concentration. The results of this study might be useful to improve the design of processing operations dealing with tomato powder reconstitution.     

Modelling the Dynamic Inactivation of the Probiotic Bacterium <Emphasis Type="Italic">L. Paracasei</Emphasis> ssp. <Emphasis Type="Italic">Paracasei</Emphasis> During a Low-Temperature Drying Process Based on Stationary Data in Concentrated Systems

In order to better understand inactivation of cells during a drying process, the inactivation kinetics of concentrated Lactobacillus paracasei ssp. paracasei (F19) was measured under stationary conditions for different combinations of water activities and temperatures in a water activity range of a _w = 0.23–a _w = 0.75 and temperatures between 4°C and 50°C. It was shown that the inactivation kinetics of the probiotic bacterium L. paracasei at moderate temperatures could, for all conditions, be formally described by a first-order reaction with activation energies that are much lower than for thermal inactivation (E _a = 61 kJ/mol). With regard to the water activity, the reaction rate constants exhibit a maximum inactivation rate at intermediate water activity a _w = 0.52. As this behavior has direct implications for the stability of cells in a drying process, the stationary data were used to model the inactivation during test vacuum drying processes, where both temperature and water activity dynamically change. It is shown that—depending on the drying rate—dynamic effects have to be taken into account when modeling the survival during drying. Nevertheless, the model based on stationary inactivation data is capable to predict the characteristics of inactivation during a drying process. Therefore, it can serve as basis to optimize the drying process with regard to maximum survival of cells. However, a further refinement of the model with regard to the drying rate is necessary.     

Effects of Applied Process on the In Vitro Digestibility and Resistant Starch Content of Pasta Products

Resistant starch (RS) included in pasta can have auspicious health benefits and functional properties. The resistance of starch, however, can be greatly influenced by the applied food preparation process. The aim of the present study was to investigate the effects of two different resistant starches on the digestibility of pasta and to predict the impact of the conventional pasta processing (extrusion under standard conditions, 120 bars, 40°C; drying in an air-drying room at 35–40°C and cooking until the optimum cooking time) on the quality of different resistant starch included in products by using an in vitro enzymatic hydrolysis method. Results showed that the applied, conventional pasta extrusion step had only a small effect on the liberated glucose level and did not influence the RS content significantly. The cooking in contrast caused an increased digestibility and the lost of resistance of all pasta products. The digestibility was significantly lower (p < 0.05) in the case of raw and dried samples compared to the cooked pastas. It can be concluded that the resistant starches used in the samples are heat sensitive and their properties change radically during the pasta preparation, mainly during cooking.     

Physicochemical and sensory properties of purple Brazilian cherry (Eugenia uniflora,L.) foams

The objective of this work was to characterise the foams of purple Brazilian cherry (Eugenia uniflora L.) pulp made with different additives, aiming at foam‐mat drying. Characterisation was made through analyses of moisture, pH, acidity, soluble solids, density, water activity, colour, total and reducing sugars, protein and ashes. Drying was done at 55 °C for 2 h. Dried Brazilian cherry juice powder was rehydrated for acceptance test. It is concluded that the physicochemical characterisation of fresh Brazilian cherry pulp was satisfactory and was in accordance with the Brazilian standards for agro‐industrial products. Albumin was the best foaming agent that produced a good‐quality powder in a short period. The foam‐mat drying of Brazilian cherry pulp using albumin and Superliga^® (Duas Rodas Industrial ltda, Santa Catarina, Brazil) as foaming agents produced a powder with good physicochemical properties and sensory quality and most preferred juice.     

Textural and physicochemical predictors of sensory texture and sweetness of boiled plantain

Boiled pulp is a major form of consumption for plantain. We assessed instrumental (puncture test and texture profile analysis) and sensory texture attributes of 13 plantain cultivars, two cooking hybrids and one dessert banana at different stages of ripeness after cooking in boiling water. Firmness, chewiness, stickiness, mealiness, sweetness and moistness described sensory variability, which was greater between stages of ripeness than between types of cultivars. Firmness and chewiness were well-predicted by instrumental force and hardness (r² > 0.72), and by soluble solid and dry matter content (r² > 0.85). Complementary sensitivity analysis revealed that a pulp puncture force or a hardness of at least 2.1 N or of 0.3 N/mm² was needed before a difference in firmness or chewiness could be perceived; a Brix of 3.7 was required to ensure a detectable difference in sweetness. Rheological and biochemical predictors can be useful for breeders for high-throughput phenotyping.