Blanched Samples Research Articles

Improvement of oleuropein extractability by optimising steam blanching process as pre-treatment of olive leaf extraction via response surface methodology

Impact of steam, hot water blanching and UV-C irradiation as pre-treatments on extraction of oleuropein and related biophenols from olive leaves (OLs), was investigated. Moreover, particle size effect of olive leaves and steam blanching duration were selected as independent variables to optimise steam blanching process in terms of oleuropein content (OC) and antioxidant activity (AC) of ethanolic extracts, by using response surface methodology. Optimum conditions for OC and AC were 10min steam blanching of 20–11 and 3–1mm olive leaf fraction, respectively. Depending on the extraction procedure, at optimum conditions of steaming the results indicate that steam blanching of OL prior to extraction can significantly increase oleuropein yield from 25 to 35 times compared to non-steam blanched sample, whereas the antioxidant activity increased from 4 to 13 times. No significant UV-C effect was observed in OC and AC, while hot water blanched samples showed significantly higher oleuropein yields and antioxidant activity compared to untreated samples.

Evaluation of some thin-layer drying models of persimmon slices ( Diospyros kaki L.)

The effect of blanching and drying temperature (50, 60 and 70 °C) on drying kinetics and rehydration ratio of persimmons under hot-air drying was investigated. It was observed that both the drying temperature and blanching affected the drying time. The shortest drying times and highest rehydration ratios were obtained from blanched samples. Six thin-layer drying models were evaluated in the kinetics research. The fit quality of the proposed models was evaluated by using the determination of coefficient ( R 2), reduced chi-square ( χ 2) and root means square error ( RMSE). The Midilli et al., Page and Weibull models showed a better fit to experimental drying data as compared to other models. Effective moisture diffusivity ( D eff ) ranged from 7.05 × 10 −11 to 2.34 × 10 −10 m 2/s calculated using the Fick’s second law. The activation energies of blanched and control samples determined from slope of the Arrhenius plot, ln( D eff ) versus 1/( T + 273.15), was 30.64 and 43.26 kJ/mol, respectively.

Effect of blanching methods on drying kinetics of bell pepper

Various blanching methods and drying temperatures were applied to bell pepper (Capiscum annum) to investigate the effect on its drying characteristics. Pepper (Capiscum annum) is an abundant and cheap source of vitamins, minerals and fibre. However, its high moisture content makes it susceptible to deterioration. The most common method of preservation is drying but the dried products obtained are of reduced nutritional qualities. Pretreatment of pepper before drying improves the quality of the dried pepper and increases its drying rate. Steam and water blanching as a form of pretreatment has been reported to increase drying rate and improve the quality of dried products but there is not much information on other types of oil/water blanching methods. The effect of blanching (steam, water, palm oil/water and groundnut oil/water) as a pretreatment on the drying kinetics of bell pepper dried at temperatures of 50, 60, 70, 80 and 90o C, was studied. Drying of raw untreated bell pepper was taken as a control. The results indicate that water removal at the initial stage of the drying process was highest and there was a rapid decrease as drying continued until equilibrium was reached at the end of process. The blanched samples generally had higher drying rates (at p<0.05) than the untreated samples. The values for the drying rate for steam and water blanched samples were higher (but not at p<0.05) than the drying rates for samples blanched in oil/water mixtures. The drying rate as well as effective moisture diffusivity, Deff, increased with increasing drying temperature. Values of Deff varied from 3.55 x 10-9 m 2/s to 2.34 x 10-9 m 2/s with the highest being SB (steam blanched) at 80oC and the lowest UB (unblanched) at 50oC. The drying process took place mainly in the falling rate period. The activation energies varied from 39.59 to 83.87 kJ/mol, with PB (palm oil/water blanched) samples having the lowest and UB having the highest Ea value. The lower values for pretreated samples imply that water movement from the internal regions is faster in pretreated samples. This suggests that blanching as a method of pretreatment generally increases water diffusion.

Proximate composition, rheological and sensory qualities of plantain (Musa parasidiaca) flour blanched under three temperature regimes

The physicochemical, pasting and sensory properties of plantain flour blanched under three temperature regimes were studied. Plantain fruit fingers were washed, hand-peeled and manually sliced into cylindrical pieces of 2 mm thickness. Blanching was carried out on the sliced samples in hot water at 60, 80 and 100°C and dried in the air oven at 65°C (24 h), while the un-blanched sample served as the control. They were milled in a hammer mill, packaged in polyethylene bags and stored in a refrigerator for further analysis. Results of analysis showed that Blanching at 60, 80 and 100°C all had significant lower moisture contents (P 0.05) from each other. On the basis of the pasting properties the peak viscosity was lower for the blanched samples (410.0 and 511.92 RVU) than the control sample (543.42 RVU). The final viscosity was highest for the control un-blanched plantain (UBPco) flour (409.33 RVU), while it ranged between 320.42 and 407.75 RVU for the blanched samples. Blanching resulted in a decrease in the bulk density of the plantain flour. Emulsion capacity decreased from 39.84% for the control sample to a range of 30.45% for sample blanched at 60°C to 17.86% for sample blanched at 100°C. Sample blanched at 60°C was scored best for taste. Samples blanched at 80 and 100°C were rated the best for colour followed by that of control and sample blanched at 60°C. The Control and the sample blanched at 60°C were rated the best in term of texture followed by that blanched at 80°C. These results showed that blanching of plantain before drying into flour had significant improvement on the physicochemical, pasting and sensory qualities of its flour. Key words: Plantain, flour, blanching, functional and pasting properties.

Drying and Rehydration Behaviors of Convection Drying of Green Peas

The drying behaviors of green peas were examined in a convection dryer for a temperature range of 55–70°C with a constant air velocity of 2.1 m/s. The green peas were pretreated with ethyl oleate and citric acid solutions and blanched with hot water at 85°C before drying. The drying process was continued until sample moisture fell to 0.3 kg water/kg dry matter (dm). The blanched samples dried faster than those in other pretreatments and control conditions. Moreover, rehydration capacities of the pretreatments were higher than control samples. The experimental results illustrated the absence of a constant rate drying period and the drying process took place in the falling rate period. Moisture transfer from green peas was described by applying Fick's diffusion model, and the effective moisture diffusivity was calculated. The calculated effective diffusivity ranged from 8.059 × 10−11 to 1.973 × 10−10 m2/s for the studied temperature range. The values of activation energy (Ea) were 22.01, 26.86, 30.31, and 30.99 kJ/mol for samples pretreated with citric acid, control samples, samples pretreated with ethyl oleate, and blanched samples, respectively. Drying data were fitted to four thin-layer drying models; namely, Lewis, Henderson and Pabis, logarithmic, and Page. The performance of the models was evaluated by comparing the coefficient of determination (R2), reduced chi-square (χ2), and root mean square error (RMSE). The models that best represented green pea drying were the logarithmic and Page models.

Efecto del Escaldado sobre la Deshidratación Osmótica del Mango

Combined treatments, such as blanching, osmotic dehydration at atmospheric pressure (OD) and pulsed vacuum osmotic dehydration (PVOD) to improve food quality (sensorial and nutritional) are a useful practice in fruit processing. Blanching reduces enzyme activity and improves color in some cases. Water activity reduction by osmodehydration (OD) with concentrated sugar/salt solutions, at low temperature, allows us to obtain minimally processed fruit or to reduce freezable water in order to improve frozen preservation. In this work, the influence of steam blanching pretreatment of mango (var. Kent) for 1.5 min on the kinetics of osmotic dehydration and pulsed vacuum osmotic dehydration was analyzed. Treatments were carried out at 30ºC with 59.3 Brix sucrose solution. At several times of processing (till 5 h) samples were analyzed as to weight and volume changes and moisture and soluble solid concentration and water activity. Kinetics of sugar and water net gains were analyzed as well as changes in the fruit liquid phase (FLP: water plus soluble solids) composition. Development of volume changes, density and water activity of the samples in the different treatments was compared. PVOD treatments show faster kinetics in solute and water gains, and slightly higher values of effective diffusivity in the FLP, especially in blanched samples. Volume changes in OD treatments were fully explained in terms of the FLP volume changes. In PVOD treatments, deviations from this behavior were observed due to sample impregnation-deformation during vacuum pulse.

Osmotic dehydration process for low temperature blanched pumpkin

This study investigated the influence of stepwise blanching over the kinetics of osmotic dehydration process and over the physical characteristics of pumpkin ( Cucurbita moschata). The 2 3 factorial design and response surface methodology was used to optimize the blanching process. The independent variables for blanching were temperature, blanching time and holding time. These independent variables showed different effects on the two studied answers: texture and color. The kinetics of osmotic dehydration were investigated using 50% and 65% sucrose solutions, using samples previously blanched by both stepwise and conventional means. The diffusivity values for the water and sucrose were similar for the two components, showing greater gains of solute than loss of water in many samples. Blanching affected the color of the pumpkin, whereas osmotic dehydration did not change it significantly. The impregnation process maintained or even increased the tissue firmness when compared to the blanched samples.

Blanching peppers using microwaves

Enzymatic reactions are not desirable in ripe fruits and vegetables. They cause losses along transportation, storage and processing. Blanching is a pre-treatment operation whose aim is to inactivate enzymes, and is usually applied before cutting, peeling, and freezing in order to avoid browning and changes in texture. Besides inactivating enzymes such as polyphenoloxidase, peroxidase and pectinase, blanching may induce sensory and chemical changes. The purpose of this work was to evaluate changes in antioxidant activity of Capsicum annuum Jalapeño type, when treating with microwaves to inactivate polyphenoloxidase. The whole fresh peppers (85% moisture) were blended until a paste was obtained. Ten grams portions were placed in a glass container and processed in a microwave oven until the inactivation of polyphenoloxidase was reached. Inactivation of the enzyme was confirmed with a spectrophotometric method using catechol as substrate. The processed peppers samples were mixed with 80% ethanol to extract phenolic compounds that were determined by the Folin Ciocalteu method. The antioxidant activity was evaluated using the radical ABTS, as described by Charurin et al (2002). Results showed that phenolic compounds were reduced from 9.6 to 7.6mg/ g peppers (dry weight basis) and antioxidant activity was enhanced from 29 to 42μM de trolox/ g peppers (dry weight basis) with thermal microwave blanching. Changes in the content of phenolic compounds were confirmed using high performance liquid chromatography, and the emergence of other phenol derivatives with enhanced antioxidant activity was detected in blanched samples. It may be concluded that blanching Jalapeño peppers with microwaves may induce the formation of derivatives of phenolics with enhanced antioxidant activity.

DRYING OF EGGPLANT SLICES IN THIN LAYERS AT DIFFERENT AIR TEMPERATURES

ABSTRACT The effect of water-blanching treatment and air temperature on drying kinetics of eggplant slices were investigated at air temperatures (50, 60, 70 and 80C). Both the blanching and air temperature influenced the drying time of eggplant slices. Moisture ratios were fitted to 11 different mathematical models using nonlinear regression analysis. The regression results showed that the logarithmic, Wang and Singh, and Midilli et al. models satisfactorily described the drying behavior of eggplant slices with highest R2 value and lowest χ2, root mean square error and residual sum of squares values. The effective moisture diffusivity increases as temperature increases and range between 5.575 and 9.745 × 10-10 m2/s for unblanched samples, and between 5.851 and 11.077 × 10-10 m2/s for blanched samples. The activation energy values of unblanched and blanched samples were estimated to be 18.27 and 20.76 kJ/mol, respectively. PRACTICAL APPLICATIONS In this study, a laboratory convective hot-air dryer was used for the thin-layer drying of blanched/unblanched eggplant slices and experimental moisture ratio was compared with 11 thin-layer drying models. The blanching treatment followed by hot-air drying may provide a practical method for the preservation of eggplant and the production of dried eggplant slices. The dried product is a valuable ingredient in the preparation of soups, premixed foods, etc.

Influence of drying conditions on the effective moisture diffusivity and energy requirements during the drying of pretreated and untreated pumpkin

Pumpkin as a fruit is consumed by both animals and humans. Its high moisture content makes it perishable and thus there is a need for drying as a means of preservation. Thin-layer drying characteristics for the samples dried using a hot-air dryer were obtained from the experiment data. The drying was observed to take place in the falling rate drying period. Ficks law was used to determine the moisture diffusivity which varied from a minimum of 1.19 × 10 −9 m 2/s for untreated pumpkin samples dried at 40 °C to a maximum value of 4.27 × 10 −9 m 2/s for steam blanched samples dried at 80 °C. The value of the energy of activation varied from 21.44 to 28.67 kJ/mol. The input energy values and specific energy requirement for thin-drying of pumpkin samples were found to be in the range of 317.8–458.1 kW h and 1588.8–2290.3 kW h/kg from 40 °C to 80 °C with a drying air velocity of 1.5 m/s respectively.

Production of dried ivy gourd sheet as a health snack

Ivy gourd ( Coccinia grandis) has recently been recognized as a rich source of β-carotene. To add value to the fresh leaves a process to produce dried ivy gourd sheet as a health snack was the aim of this study. The effects of pretreatment, i.e., blanching in NaCl solution (0–3% w/v), and drying methods, i.e., hot air drying and vacuum drying at 60–80 °C, on the drying characteristics and quality, viz. colour, texture and β-carotene content of dried ivy gourd sheet were investigated. The results showed that dried sheet pretreated by brine blanching and vacuum drying resulted in better retention of colour and β-carotene as well as texture of the dried sheet as compared to the dried untreated and dried water blanched samples. Higher drying temperature also resulted in higher β-carotene retention due to shorter drying time.

Effect of Processing on Major Carotenoid Levels in Corn (Zea mays) and Selected Vegetables: Bioavailability of Lutein and Zeaxanthin from Processed Corn in Mice

Corn and vegetables are good sources of vitamins, minerals, and carotenoids. This study reports (1) the effect of processing—blanching, drying, and milling on major carotenoids—lutein (L), zeaxanthin (Z), and β-carotene levels in corn (Zea mays), onion stalk (Allium cepa L), broccoli (Brassica oleracea L), and capsicum (Capsicum annum L), and (2) the bioavailability of L and Z from processed corn in mice. A group of mice were fed with diet containing processed or unprocessed corn (L + Z source) or purified L (control) for 3 weeks. Results from HPLC analysis indicate that the levels of L + Z (19.6–118.5%) and β-carotene (1–84%) were higher in blanched samples compared to fresh samples whereas drying resulted in lower L + Z level in onion stalk (45.5%) and capsicum (36.4%) and was higher in corn (22%) and broccoli (14%) over blanching. The level of β-carotene was slightly higher in broccoli on drying than blanching. Milling did not alter carotenoid levels in any of the samples. Feeding processed corn (blanched + dried + milled) resulted in nonsignificant change in the plasma L + Z level but significantly higher in liver (58.7%) than in control group. Similarly, the level of L + Z in plasma (12.1%) and liver (14.9%) of mice fed on processed corn was higher compared to unprocessed-corn-fed group. Based on the above results, it is concluded that the extractability and bioavailability of L + Z can be improved by blanching corn before its consumption.

Influence of Sous Vide and Water Immersion Processing on Polyacetylene Content and Instrumental Color of Parsnip (Pastinaca sativa) Disks

The effect of blanching (95 +/- 3 degrees C) followed by sous vide (SV) processing (90 degrees C for 10 min) on levels of two polyacetylenes in parsnip disks immediately after processing and during chill storage was studied and compared with the effect of water immersion (WI) processing (70 degrees C for 2 min.). Blanching had the greatest influence on the retention of polyacetylenes in sous vide processed parsnip disks resulting in significant decreases of 24.5 and 24% of falcarinol (1) and falcarindiol (2) respectively (p < 0.05). Subsequent SV processing did not result in additional significant losses in polyacetylenes compared to blanched samples. Subsequent anaerobic storage of SV processed samples resulted in a significant decrease in 1 levels (p < 0.05) although no change in 2 levels was observed (p > 0.05). 1 levels in WI processed samples were significantly higher than in SV samples (p <or= 0.05). 2 was particularly susceptible to aerobic storage following WI processing with losses of up to 70% occurring after 5 days storage. 1 type polyacetylene undergoes degradation such as oxidation, dehydrogenation when thermally treated forming oxidized form of 1 type molecules, in this case falcarindione, dehydrofalcarinol, dehydrofalcarinone. Thermal processing had a significant effect on instrumental color of parsnip samples compared to minimally processed in both SV and WI processed samples resulting in parsnip disks becoming darker, yellower and browner following processing and storage.

Sensory and antioxidant properties of Okra Abelmoschus esculentus (l) moench as affected by processing and storage temperature

Quality attributes of frozen okra as influenced by processing and storage techniques were investigated extensively. Okra samples were water blanched at 980C for 3 minutes and steam blanched at 100oC for 5 minutes. Both blanched and unblanched samples were stored in a freezer at -18oC for 120 hours. The sensory evaluation, antioxidants, and chlorophyll contents were evaluated at 24 hours interval for 5 days. From the results of sensory evaluation, water blanched okra were rated the best in all the parameters at the end of the storage period. The total phenol reduced significantly (p > 0.05) on blanching (0.11-0.007% water blanched and 0.11-0.09 steam blanched) and increased significantly (p > 0.05) during storage. The vitamin C reduced after blanching and during storage significantly (p > 0.05). The chlorophyll content of okra reduced significantly (p > 0.05) after blanching and in storage at -18oC. Chlorophyll a decreased but chlorophyll b increased during the first 48 hours of storage and then decreased as the storage period increased. In sensory evaluation, water blanched samples were more acceptable but steam blanched samples retained more of the antioxidants and chlorophyll. Therefore there must be compromise between palatability and antioxidants.

INFLUENCE OF PRETREATMENTS ON THE DEHYDRATION CHARACTERISTICS DURING VACUUM DRYING OF WATER DROPWORT (OENANTHE JAVANICA DC.)

The thin-layer drying behavior of water dropwort in a laboratory scale vacuum dryer was examined. Two pretreatments (blanching and 1% KMS dipping) were applied to the water dropwort, which were dried in the ranges of 50–70C of drying air temperature. The drying air temperature and pretreatment had significant effects on the moisture content of the water dropwort samples. In all the drying temperature selected, the blanched samples had shorter drying time than the control and 1% KMS treated samples. The drying rate decreases continuously with decreasing moisture content or increasing drying time. The models were compared based on the coefficient of determination, reduced chi-square and root mean square error between the observed and predicted moisture ratios. The Page model has shown a better fit to the experimental drying data as compared to other models. The color characteristics of dried water dropwort were also significantly influenced by the pretreatments. PRACTICAL APPLICATIONS The information on the drying characteristics of water dropwort as influenced by pretreatments may provide a practical method for the preservation of water dropwort and improvement on the quality of dried products. The experimental data are necessary to design, optimize, and control the drying process in the production of dehydrated water dropwort products.

Hot air drying of yacon (Smallanthus sonchifolius) and its effect on sugar concentrations

SummaryThis work aimed to experimentally study the drying behaviour of yacon tubers with and without steam blanching. Drying was carried out for 5 h and 30 min in a forced air dryer at 50 °C, 60 °C and 70 °C. The results indicated that the shortest drying time was obtained at 70 °C for blanched samples, and that the equilibrium water activity values were significantly lower for the blanched samples at all temperatures. The yacon dried without prior blanching showed lowest concentrations of reducing sugars when dried at 70 °C, significantly lower than those dried at 50 °C and 60 °C. This indicates hydrolysis of the fructo‐oligosaccharides at 70 °C, a fact verified by the significant increase in reducing sugars content from 36.65 ± 0.54–44.10 ± 0.96% and reduction in the non‐reducing sugars from 31.62 ± 0.55–26.18 ± 0.29%.

P137 The pediatric HIV experience in Manitoba, Canada from 1989 to 2007

Freeze dried raw (FDR) and freeze dried blanched (FDB) Amorphophallus paeoniifolius flours were irradiated at doses of 3, 6 and 12 kGy. The irradiated flours were investigated for physicochemical, pasting, textural, thermal and morphological properties. Reduction in amylose content was observed with increasing irradiation dose. Carboxyl content of the flours increased significantly at higher doses. Decline in lightness (L∗) and increase in redness (a∗) were found to increase with the elevation of dosage. Irradiation caused reduction in the values of pasting parameters of freeze dried raw as well as freeze dried blanched samples. Hardness of the flour gels exhibited increase at all the doses except at 3 kGy. Decrease in onset gelatinization temperature of both FDR and FDB flours was observed with increasing irradiation dose. FDR as well as FDB flours exhibited increasing trend in their enthalpy (ΔHgel) values following irradiation treatment. Raman spectroscopy revealed that no new functional groups were introduced by irradiation treatment. However, band intensity of functional groups in irradiated FDR flours was reduced with increment of dose.

EFFECT OF HIGH‐PRESSURE PROCESSING ON TEXTURE AND DRYING BEHAVIOR OF PINEAPPLE

ABSTRACT The effect of high‐pressure processing on texture and drying behavior of pineapple slices was investigated. Pineapple slices were high pressure processed at 50, 100, 300, 500 and 700 MPa at 25C for 10 min. The control, hot water‐blanched and high‐pressure processed samples were then dehydrated at 70C. Application of high pressure reduced the sample hardness, springiness and chewiness while it had no significant effect on cohesiveness of pineapple. Elevated pressure treatment (≥500 MPa) reduced drying time more effectively than for the other pretreated samples. Experimental dehydration data were empirically fitted using six thin‐layer drying models. Among the models tested, logarithmic model best described the drying behavior of pineapple slices. The effective moisture diffusivity was found to increase with an increase in the level of pressure up to 500 MPa, and the samples processed at 500 and 700 MPa had higher diffusivity values than blanched samples. PRACTICAL APPLICATIONSThis work shows that high‐pressure blanching of pineapple can be an alternative for hot water blanching, before dehydration. The results may find application in development of quality snack food from pineapple fruits.

INFLUENCE OF A BLANCHING PRETREATMENT ON COLOR, OIL UPTAKE AND WATER ACTIVITY OF POTATO STICKS, AND ITS OPTIMIZATION

ABSTRACT The objective of this research was to study the influence of different blanching conditions on potato stick color, oil uptake and water activity (Aw ), and optimize the process by means of the desirability function. Color was expressed as properties of L*a*b*and L*C*h*spaces, some of which were fitted by Box–Behnken quadratic models. The blanching optimum conditions were as follows: a concentration of ascorbic acid of 0.2 g/100 g potato, a time of 5.5 min and a temperature of 69C. Responses obtained when using these conditions were −1.68 a*value and −86.31° h*value, which represent a hue in potatoes unaffected by the enzymatic browning. Regarding oil uptake, some of the blanched sticks absorbed 31% less oil than the control. Regarding Aw, all blanched samples presented lower values than the control, suggesting that blanching increases the shelf life of fried potatoes.PRACTICAL APPLICATIONSThis article presents that the optimized blanching process conditions were able to control the enzymatic browning in potato sticks prior to frying, and thus improved their quality. Furthermore, some blanching conditions were found to decrease by 31% the oil uptake in potato sticks, leading to healthier fried potatoes. Finally, blanching significantly decreased the Aw in all fried potato sticks evaluated, suggesting that this process is also a way to increase the shelf life of fried potatoes.

Evolution of Volatile Fraction and ATP Related Compounds During Storage of Desalted Cod (Gadus morhua)

The objective of this work was to study the evolution of the volatile fraction, and ATP and its breakdown products, in desalted cod thermally treated (water blanching, steam blanching and microwave heating), stored at 4 °C. All analyses were carried out at 0, 7, 14, 21, and 28 days of storage, as in the treated samples as in the control samples (desalted cod without thermal pre-treatment). The study of the volatile fraction revealed a similar behavior of the water blanched and steam blanched samples, by one hand, and of the control samples and those treated with microwave, on the other hand. This fact would imply a lower effectiveness of the microwave treatment on the preservation of the initial odor of desalted cod. The initial K1-values were lower in control and microwave samples than in water and steam blanched samples. However, the higher increase of K1-values throughout the storage in control and microwave samples would indicate a higher spoilage for these samples during the studied period. According to these results, the two blanching treatments were more effective than microwave heating in the preservation of desalted cod.