Microwave Blanching Research Articles

Shaping the Physicochemical and Health-Promoting Properties of Carrot Snacks Produced by Microwave-Vacuum Drying with Preliminary Thermal and Enriching Treatment.

This study analyzed the effects of thermal pre-treatments such as convective drying (P-CD), water (BL_W), and microwave blanching (M_BL) and osmotic enrichment pre-treatments with juices from pomegranate (PG), chokeberry (CH), and sea buckthorn (SB) on microwave-vacuum-dried (MVD) carrot properties. Convective drying (CD) and freeze-drying (FD) were used as a comparative method. The dry matter content and water activity of MVD carrots were varied, but in many cases, the values were comparable to those of FD-dried carrots. Pre-enrichment in CH juice significantly reduced the values of the color parameters L*, a*, and b*, regardless of the drying method. The smallest changes were observed in microwave pre-blanching (M_BL). The lowest loss in carotenoid content was observed in CD-dried carrots (14-34 mg/100 g d.m.). Blanching and enrichment in SB juice allowed significant retention of these compounds. As a result of drying carrots, the total phenolic content (TPC) increased. Compared to the raw material, the TPC content in dried carrots increased 3-9 times. Drying using the FD and MVD methods gave a similar effect of increasing the TPC content, including a greater effect after enrichment in CH juice. The highest average antioxidant activity against the DPPH• and ABTS•+ radicals was recorded for FD-dried carrots (6.9 and 30.0 mg Trolox/g d.m.). SB juice contributed to a significant increase in the total vitamin C content, even by 89.1%, compared to raw carrots. Applying osmotic pre-enrichment in PG juice increased the sugar content in dried FD and CD samples by 37.4-49.9%, and in MVD by 21-59%.

Comparative study on enzyme activity, microstructure, drying kinetics, and physicochemical properties of apple slices affected by microwave and steam blanching

Comparative study on enzyme activity, microstructure, drying kinetics, and physicochemical properties of apple slices affected by microwave and steam blanching

The influence of pretreatments on the quality characteristics and in vitro biological activity of freeze-dried Thai Tom-Yum ingredients

This study aimed to investigate the effects of pretreatments on quality characteristics, bioaccessibility of phenolic compounds, and antioxidant activities (AA) of freeze-dried Thai Tom-Yum ingredients during in vitro digestion. Hot water (B), steam (S), microwave blanching (MW), ultrasound (US), and blanching with dipping in chemical solution (D) were performed on lemongrass, red onion, kaffir lime leaves, chili, galangal, and coriander. In most samples, D significantly lowered water activity (Aw) and moisture content (MC) while preserving color attributes. D was the best pretreatment with the highest total phenolic compounds (TPC) for lemongrass, red onion, and galangal, US for kaffir lime leaves and chili, and S for coriander. The AA assessed by DPPH and FRAP showed a correlation with TPC values (0.731 and 0.576 at p < 0.01). Bioaccessibility of phenolic compounds and FRAP in selected herbs were higher under intestinal phase. After digestion, kaffir lime leaves treated with US had the highest TPC and FRAP values, ranging from 26.63 to 34.34 mg GAE/g db and 80.07–105.07 μmol FeSO4/g db, respectively. A decrease in DPPH values was observed in lemongrass, red onion, chili, and galangal. These findings show that pretreatments and freeze-drying have considerable effects on the qualitative attributes, bioaccessibility of phenolic compounds, and AA of dried herbs.

Quality attributes of dehydrated pear (Pyrus communis L.) as affected by conventional and novel blanching techniques

ABSTRACT A study was conducted to assess the impact of different blanching methods and blanching time on the quality of dried pear slices. Pears are only available seasonally, making the production of high-quality dried slices a valuable commodity. The pears were prepared and sliced before being blanched using three different methods: traditional blanching with hot water, blanching with steam, and microwave blanching for varying lengths of time. After blanching, the slices were cooled and then placed on filter papers to dry. The dried slices were then evaluated for chemical properties, such as sugars, total soluble solids, titratable acidity, ascorbic acid, Brix/acid ratio, ash content, and moisture content. Sensory properties such as color, taste, texture, and overall acceptability were also evaluated using a 9-point hedonic scale. The data generated were analyzed using a two-way analysis of variance (ANOVA) to determine the significant differences between variables. The results showed that the blanching method used had a non-significant effect (p < .05) on the chemical properties of the pear slices, such as total sugars (reducing and non-reducing), total soluble solids, titratable acidity, ascorbic acid, Brix/acid ratio, ash content, and moisture content. However, there was no significant effect on the sensory properties of color, texture, taste, and overall acceptability. In conclusion, blanching is an effective technique for preventing microbial growth and chemical and enzymatic reactions that can lead to the deterioration of dried pear slices. It also helps to remove moisture without adversely affecting the physicochemical and sensory quality attributes of the final product.

Rehydration modeling and characterization of dehydrated sweet corn.

The increasing demand of rehydrated foods is due to its better storage stability at ambient conditions and not requiring refrigeration. Prior to drying at 55, 60, 65, and 70°C in a hot air tray dryer, hot water blanching (HB), steam blanching (SB), and microwave blanching (MB) were employed as pretreatments. Rehydration of dried pretreated sweet corn kernel was performed in boiling water. The pretreatments and drying temperatures were independent factors that affected the dependent factors such as rehydration ratio, total sugar, ascorbic acid, geometric mean diameter, color, sensory evaluation, water absorption, mass, and geometric mean diameter. Peleg, Weibull, and newly proposed models were considered to describe the change in moisture content during rehydration. The proposed model performed better than other models and indicated the rise in equilibrium moisture content of rehydrated sweet corn with an increase in dehydration temperature of sweet corn due to higher R 2 (0.994), and lower chi-square (0.005) and RMSE (0.064). The rehydrated sweet corn obtained from samples processed with microwave blanching and dehydration at 70°C showed higher retention of total sugar, ascorbic acid, geometric mean diameter, and color.

Evaluation of dry microwave and hot water blanching on physicochemical, textural, functional and organoleptic properties of Indian gooseberry (Phyllanthus emblica)

Indian gooseberry (Phyllanthus emblica) is a seasonal and highly nutritious fruit with shorter shelf-life and astringent taste limiting its utilization. The enzymatic browning and flavor loss are major concerns which makes pre-processing a crucial step for further processing. In this context, dry microwave blanching (MWB) was explored as an alternative to hot-water (HW) blanching to reduce its nutrition losses particularly ascorbic acid (AA) and makes it easier for removal of seed kernel. This study focused on the effect of MW power level (200–500 W) and blanching time (50–100 s) on AA content, color attributes (L*, a*, b*), and enzymatic inhibition in Indian gooseberry. The optimized MWB conditions were 294 W MW power with 70 s blanching time providing satisfactory enzymatic inhibition (75.47%), and retention of AA (417.70 mg/100 g pulp) and color attributes (L*: 58.42, a*: 4.57, b*: 26.23). As compared to HWB (80 °C, 5 min), MWB showed least AA degradation, higher total phenolic content and softening percent with less total color difference owing to its shorter processing time and dry blanching. Quantitative descriptive analysis (QDA) demonstrated that raw and MW blanched Indian gooseberries are the most accepted, followed by HW blanched samples. MWB showed better nutrient retention than HWB with easier seed removal showed the application of MW radiation for blanching of other fruits.

A comparative study of electrical and conventional pre-treatments for quality assessment of hot air dried green bell pepper.

In this study, the effect of pretreatments (hot water blanching, microwave blanching and ohmic heating) on drying kinetics and quality characteristics of green bell pepper dried at 60, 70 and 80 °C was investigated. Four mathematical models were fitted to experimental data and Logarithmic model was found to be the best for all the samples. Rehydration ability of only ohmic heating pretreated peppers was higher than untreated ones. Total polyphenol (TP) content and antioxidant capacity (AC) of dried peppers varied between 3.21-5.08 mg gallic acid equivalent (GAE)/g dry matter (DM) and 1037.57-2407.40 mmol AAE/100 g DM, respectively. The content of ascorbic acid (AA) in dried samples was in the range of 187.25-722.55 µg/g DM. The bioaccessibility of TP after in-vitro digestion varied from 79.44 to 97.73%. Losses of chlorophyll a and b were very high in all samples compared to fresh ones but the most in control samples.

Влияние технологических параметров на качество травяного напитка из зеленой спаржи (Asparagus officinalis L.)

Green asparagus is widely consumed fresh due to its high nutritional value and a low calorie content. However, its short shelf-life due to a high water content causes high postharvest losses. In this study, we aimed to develop an innovative asparagus herbal drink to ease postharvest losses and diversify asparagus-derived products.&#x0D; We investigated the effects of process parameters on the quality of the herbal drink from green asparagus. In particular, we determined the optimal length and grinding size for asparagus and selected suitable blanching and drying methods. Analytical responses included the contents of total soluble solids, polyphenol, carbohydrates, and vitamin C, as well as the visual appearance of asparagus samples. &#x0D; The length of 5 mm was found suitable for subsequent steps as it facilitated an increase in solute in the asparagus infusion. Microwave blanching and convective drying were selected to achieve high contents of total soluble solids, polyphenol, carbohydrates, and vitamin C in the asparagus infusion. Dried asparagus ground into 1.5–2.0 mm particles was packaged into tea bags. The asparagus infusion subjected to sensory evaluation had a yellowish color, a characteristic asparagus flavor, and a relatively sweet taste. Total soluble solids in the infusion amounted to 26%. &#x0D; Our results showed a possibility of developing an asparagus herbal drink which could be a potent product in the commercial market. Therefore, further large-scale studies of the asparagus herbal drink should be carried out to enhance its feasibility in the food industry.

Effect of Hot Water, Steam and Microwave Blanching on Colocasia esculenta Leaves

Blanching, a pre-processing procedure, is usually carried out to inhibit enzymatic and other reactions which contribute to loss of quality prior to processing of green leafy vegetables. In this work the effect of hot water, steam and microwave blanching on peroxidase inactivation, colour changes, ascorbate degradation and changes in phenolic content of C. esculenta leaves was studied. Hot water and steam blanching were carried out in boiling water and steam, respectively, for 10, 20, 30, 60 and 120 s while microwave blanching was carried out for 5, 10, 15, 20 and 30 s. Peroxidase inactivation was faster in microwave blanched leaves. A 90% inactivation of peroxidase was achieved within 15 s of microwave blanching compared to 120 s and 30 s of hot water and steam blanching, respectively. The highest change in colour (ΔE) and chroma was observed after 20 s of microwave and steam blanching, respectively, although the changes were not significant. All the different blanching techniques resulted in ascorbate degradation, although higher losses were observed with hot water blanching compared to steam and microwave blanching.

Mathematical modelling and characterization of drying of pre-treated sweet corn (Zea mays L.) kernels.

The pre-treated sweet corn samples were dried at temperatures of 55, 60, 65 and 70°C and thin layer drying characteristics of sweet corn were assessed. Mathematical models were fitted and evaluated using R2, χ2, RMSE values. The effective diffusivities for the drying process were 4.32 × 10-10 to 1.08 × 10-9m2/s and activation energies were 34.51 to 38.99kJ/mol. Total sugar and ascorbic acid of dehydrated sweet corn kernels varied from 5.50 to 13.00g/100g and 3.30 to 10.50mg/100g respectively. The sample pre-treated with microwave blanching and dried at 70°C obtained higher sensory score after rehydration, indicating suitability of the dehydrated sweet corn.

Physicochemical characteristics of sweet corn kernels during microwave blanching

Sweet corn kernels are easily perishable because of their high amount of moisture content. Microwave blanching was applied at the power level of 180–900 W for 30–70 s to inactivate the enzymes of sweet corn kernels. The increase in microwave power level and processing time reduced the length from 11.13 to 10.78 mm, width from 9.54 to 9.24 mm, thickness from 4.01 to 3.71 mm, true density from 1052.07 to 1012.03 kg/m3, porosity from 37.43 to 24.54%, moisture content from 70.00% to 68.93% on a wet basis, total soluble solid from 22.3 to 18.7 °Brix, total sugar from 8.80% to 6.67%, ascorbic acid from 8.04 to 5.92 mg/100 g, and peroxidase activity up to 1.37% in sweet corn kernels, but it increased the bulk density from 658.23 to 763.6 kg/m3 and total color difference up to 14.55. Novelty impact statement The microwave blanching was found adequate for processing sweet corn kernels at the power level of 720 W for a short duration of 40 s to achieve a 90% reduction in peroxidase activity. The ascorbic acid, total sugar, overall acceptability after the microwave blanching were 6.86 mg/100 g, 7.87%, and 8.21, respectively, indicating 85, 89, and 94% retention of fresh samples properties. The total plate count was 9.1 log cfu/g in fresh kernels, which was also reduced to 1.8 log cfu/g in kernels blanched at the power level of 720 W for 40 s duration.

TECHNOLOGY OF APPLE COMPOTE PRODUCTION FOR BABY FOOD WITH A HIGH CONTENT OF NATURAL INGREDIENTS

The most promising direction of improving food technologies for baby food is the use of new technical solutions that ensure maximum preservation of natural ingredients contained in the initial plant raw materials in the finished product. To do this, instead of the traditional process of blanching in water, microwave blanching is proposed directly in glass jars in microwave EMF (ultrahigh frequency electromagnetic field) with a frequency of 2400 MHz for 1.5 minutes, after which syrup is poured at a temperature level of 980C, prepared with the addition of infusion extracted from secondary products, followed by sealing of cans and sterilization according to a new gentle sterilization regime with a preliminary increase in the temperature level of the semi-finished product by processing it in microwave EMF before sealing cans, for 1.5 min.

Development and optimization of gluten‐free biscuits with carob flour and dry apple pomace

The objective of the present work was the formulation, optimization, and quality evaluation of gluten-free biscuits at different water levels, based on a rice and carob flour mixture enriched with dried apple pomace, prepared with, and without microwave blanching (MB). MB contributed to the partial conversion of insoluble dietary fiber to soluble. Increasing dried apple pomace proportion in the mixture resulted in higher sensory aroma and hardness and higher brightness (L*) and red hue (a*). On the other hand, the increase in water level caused a rapid increase in biscuits moisture and a drastic reduction of sensory hardness and crispness, and of mechanical fracture force and spread factor. Sensory hardness and crispness were positively correlated with mechanical fracture force and spread factor (W/T). Three biscuit formulations with % levels (A:C:W) of apple pomace (A), carob flour (C), and water (W) were found to score highest (34:16:50, 32.5:32.5:35, 49:16:35). Novelty impact statement Apple pomace combined with rice and carob flour in gluten-free biscuits could improve physicochemical, textural, and sensory characteristics. From a nutritional aspect, the final products can be considered as a rich source of dietary fiber thus enhancing their nutritional quality. It is expected that the results from the present work can impact positively on the successful production of gluten-free biscuits providing new ideas for innovation in the food industry.

Impacts of novel blanching treatments combined with commercial drying methods on the physicochemical properties of Irish brown seaweed Alaria esculenta

Alaria esculenta is one of the most abundant edible brown seaweeds in Irelandandisconsidered an excellent source of nutrients, sought after by the food, nutraceutical and pharmaceutical industries. Seaweed is typically blanched and dried prior to consumption to enhance the end-product quality attributes and shelf life. Three blanching techniques were examined in this work; conventional hot water blanching, novel ultrasound blanching and microwave blanching. The L* and b*colour metrics were affected significantly (P < 0.01) by the processing methods. There were 76 volatile compounds detected in blanched and dehydrated Alaria esculenta. Freeze-dried samples after treatment with microwave alone (at 1000 W) and microwave (800 W) combined with ultrasound (at 50% amplitude) had the highest retention rate of volatile compounds (up to 98.61%). Regarding mineral content, drying methods significantly affected (P < 0.05) the content of Ca, Co, Cu and Fe, while blanching treatments significantly affected (P < 0.05) the content of Na, Cu, Fe and Mn.

Synergetic effect of microwave blanching and modified atmosphere packaging using laser micro-perforated bags on the storage quality of carrot

Synergetic effect of microwave blanching and modified atmosphere packaging using laser micro-perforated bags on the storage quality of carrot

Organoleptic Test of Green Mustard Leaf Flour (Brassica juncea) Due to Various Types of Preliminary Treatments

This study aims to determine the effect of preliminary treatment on the quality of organoleptic green mustard leaf flour.This research was conducted in the Laboratory of prodak development of Muhammadiyah University sidoarjo from February to April 2020 using descriptive methods. The experiment was compiled in a Complete Randomized Design with variations of preliminary treatment conducted ie without blanching (TPP), water blanching (PPR), water blanching with soaking salt solution 1% (PPRG 1), water blanching with soaking salt solution 2% (PPRG 2), water blansing by immersion of 0.1% na metabisulfite solution ((PPRN 1), water blanching by immersion of 0.2% na metabisulfite solution (PPRN 2), steam blanching (PPK) and microwave blanching (PPM). Based on organoleptic tests showed that the preliminary treatment had a noticeable different effect on color and aroma.The best treatment in the manufacture of mustard flour hijua with preliminary treatment is steam blansing that gives a normal value of 0.98 with organoleptic characteristics of color 6.04 (likes-very likes) and organoleptic aromas of 6.12 (likes-very likes).

Effect of Various Blansing Treatment and Drying Temperature on Organoleptic Characteristics of Mustard Leaf Stalk Flour (Brassica juncea)

This study aims to determine the effect of blanching method and drying temperatures on organoleptik properties of mustard stalk flour. The study was conducted at the Development Product and Food Analysis Laboratory of Muhammadiyah Sidoarjo University from March to May 2020 used basic descriptive method. The sample used was mustard greens stalk. Various blanching method used without blanching, water blanching, steam blanching, and microwave blanching. Various temperature used cabinet drying at 55°C and 65 oC. The result showed there was different characteristic organoleptik of mustard stalk flour between blanching method and drying temperature. The best treatment was mustard stalk flour that used steam blanching and drying temperature 55 oC that show hedonic test of colour 3,47, texture 3,10, and aroma 2,43.

Effects of various blanching methods on fucoxanthin degradation kinetics, antioxidant activity, pigment composition, and sensory quality of Sargassum fusiforme

This paper aims to study the effects of hot water blanching, salt water blanching, microwave blanching, and steam blanching on the quality of Sargassum fusiforme using different detection indicators, such as fucoxanthin content, pigment composition, antioxidant activity (2,2-diphenyl-1-picrylhydrazyl and hydroxyl radical scavenging ability), and sensory quality. Results revealed that the blanching treatment exhibits dual effects of promoting dissolution and degradation of fucoxanthin. Besides hot-water blanching with 98.3 °C, the other three methods were not conducive to the retention of fucoxanthin. The Weibull model provides a good description of the degradation kinetics of fucoxanthin during blanching. For the radical scavenging assay, the extract obtained by microwave blanching had the strongest activity, followed by steam blanching. However, the other two kinds of blanching with water were not conducive to retaining activity. Sensory analysis revealed that the sensory quality could be better restored by blanching for a shorter time. Finally, the following three essential blanching conditions were selected from all the tests: the best pretreatment condition for fucoxanthin extraction: hot water blanching at 60 °C for 12 min; the best antioxidant activity: microwave blanching for 8 min; the best sensory quality: microwave blanching for 2 min.

Microwave and steam blanching as pre-treatments before air drying of Moringa oleifera leaves

The objective of this work was to identify the optimal drying conditions to produce better quality dried Moringa oleifera leaves with the best drying kinetics using microwave and steam blanching pre-treatments prior to hot air drying. For this purpose, the effect of microwave power, microwave time, steaming time, and air temperature on drying kinetics and quality of Moringa leaves was evaluated using the response surface methodology. In order to achieve a moisture content of 8.0% kg H2O/kg dry matter, the optimal conditions identified were a steaming time of 2.58 min (2 min 35 sec) prior to air drying at 70°C and a microwave power of 270 W for 3 min, followed by air drying at 70°C. At this optimal condition, a confirmation test for steam-assisted air drying gave a drying time (DT) of 53 min, ascorbic acid (AA) of 2.49 mg/g, and the antioxidant activity (AOA) of 67.244% inhibition. For microwave-assisted air drying, the confirmation experiment gave a DT of 43 min, AA of 2.699 mg/g, and AOA of 74.46% inhibition. Both pre-treatments before air drying followed a falling rate drying period at the initial stages and later a constant rate drying period. Our results showed that microwave blanching should be considered as a pre-treatment in industrial production of Moringa leaves to produce better quality dried products in a relatively short time.

Assessment of pretreatments on drying kinetics and quality characteristics of thin-layer dried red pepper

In this study, the effect of pretreatments (hot water blanching, microwave blanching, and ohmic heating) on the drying kinetics and quality characteristics of red pepper, dried at 60 and 70 °C, was investigated. The drying times varied between 205–290 min, depending on the pretreatment and temperature applied. The drying rate also changed based on the pretreatment and the falling rate period was observed. Four mathematical models were fitted to experimental data and the logarithmic model was found to be the best for all of the samples. Effective moisture diffusivity values obtained from Fick’s second law of diffusion ranged from 6.11 × 10–10 to 9.31 × 10–10 m2 s–1. The total phenolic contents, antioxidant capacities, and red pigment amounts of the dried peppers varied between 6.95 and 9.45 mg GAE g–1dry matter (DM), 2610.43 and 4463.96 mmol AEAC 100 g–1DM, and 184 and 443mg 100 g–1DM, respectively. Rehydration ability of pretreated samples was similar to or slightly lower than that of the untreated samples. As a result, it can be suggested that ohmic heating before drying at a temperature of 70 °C could be a promising alternative pretreatment to decrease drying time and produce high-quality dried red pepper.