Microwave Baking Research Articles

MODELING OF HEAT AND MASS TRANSFER DURING BAKING OF BISCUITS

Precooked biscuits (7 cm diameter x 2 cm thickness), preserved by freezing, were evaluated in a regional bakery. Heat and mass transfer during these processes and through the final baking were studied. Precooking was conducted at 180C for 18 min; convection and conduction were the predominant phenomena for heat transfer, with an a = 1.71 x 10 - 7 m 2 /s. Diffusion mechanism adequately modeled (r 2 = 0.94, PEM < 2.5%) the moisture loss during cooking stage, with a D = 1.04 × 10 - 6 m 2 /s. The freezing point obtained inside a tunnel freezer (forced air at -40C), was -6.73C, consistent with the predicted value. Volume changes were minimal during frozen storage because of high fat content and few variations in the freezer temperature. Final baking in conventional gas and microwave ovens were compared. Higher moisture loss and minimal color change occurred in the microwave baking. Instrumental texture of both final treatments were significantly different, in contrary to sensory evaluation (a = 0.05). The methods produced a good choice for product commercialization after baking.

EFFECTS OF BAKING PARAMETERS ON THE WHITE LAYER CAKE QUALITY BY COMBINED USE OF CONVENTIONAL AND MICROWAVE OVENS

The effects of combined conventional and microwave oven baked white layer cake characteristics were studied. Two types of commercially milled wheat flour, white (A) and whole wheat (B), were used. The modified white layer cake making method was used for conducting the cake baking trials. The conventional baking times (8 or 11 min), microwave power (400 or 600 W) and microwave baking time (30, 40, or 50 s) were chosen as baking parameters. Conventional baking was applied to form the cake crust before baking with the microwave oven used to form the crumb of the cakes. The performance of combination baking was compared with the performance of conventional baking. The volume, bake loss, internal factors, and crust color of cakes were evaluated as quality characteristics. The bake losses of cakes using the combination of short oven times and low microwave power for selected microwave times were smaller than the bake losses of the control cakes for both flours. Long oven times and low microwave power increased the specific volume of cakes. Cakes baked from flours A and B exhibited similar internal properties. Oven time significantly affected the crust color of cakes made with flour A. The crust color of cakes made with flour B was similar to the crust color of control cakes. Using a combination of conventional and microwave baking produces cakes with qualities equivalent to the qualities of cakes produced with conventional baking.

Inactivation of trypsin inhibitors in sweet potato and taro tubers during processing.

In order to understand the extent of elimination of trypsin inhibitors during processing of sweet potato (Ipomoea batatas) and taro (Colocasia esculenta) tubers, a detailed study was conducted using tubers processed by oven drying, cooking, and microwave baking. Between 80 and 90% trypsin inhibitor (TI) activity was retained in sweet potato chips up to 2h at 70 degrees C. Among the four cultivars of sweet potatoes, RS-III-2 trypsin inhibitors were more heat labile. Heating at 100 degrees C led to rapid inactivation of TI of sweet potatoes. Varietal differences in thermal stability were more pronounced for the trypsin inhibitors of taro than sweet potatoes. Taro inhibitors were also more rapidly inactivated than sweet potato TI. Between 17 and 31% TI activity was retained in cooked tuber pieces of sweet potatoes, while only 3-10% were retained in taro cultivars. Very effective inactivation of trypsin inhibitors of sweet potatoes and taro could be obtained through microwave baking. Flour prepared from taro was devoid of TI activity, while 5-12% TI activity was retained in the flour prepared from sweet potatoes. The study clearly established that among the four techniques used, microwave baking and flour preparation were the best methods to eliminate TI from sweet potatoes and taro.

Comparison of the volatile components of two cultivars of potato cooked by boiling, conventional baking and microwave baking

AbstractTubers of two cultivars (Estima and Maris Piper) of potato were cooked by three different procedures, ie boiling, conventional baking and microwave baking. Peeled and sliced tubers were boiled, while intact potatoes were baked in their skins. Flavour components from the boiled slices and the flesh of the baked tubers were isolated by headspace adsorption onto Tenax and analysed by gas chromatography–mass spectrometry (GC–MS). For all cooking procedures, Estima gave stronger isolates than Maris Piper. The two main sources of flavour compounds (regardless of cooking procedure) were lipid degradation and the Maillard reaction and/or sugar degradation. The ratio (yield derived from lipid)/(yield derived from Maillard reaction and/or sugar) decreased from 8.5–9.1 (boiling) to 2.7–3.4 (microwave baking) and to 0.4–1.1 (conventional baking). Quantitative and qualitative differences among the cooking procedures are explained in terms of the variations in heat and mass transfer processes that occurred. Each cooking procedure resulted in a unique profile of flavour compounds.© 2002 Society of Chemical Industry

Transfer of heat and moisture during microwave baking of potatoes

AbstractMicrowave baking of potatoes comprised two phases. In the first phase the internal temperature of the potatoes rose to approximately 100 °C with little loss of water vapour. The uniformity of internal heating during this phase was assessed by identifying gelatinised starch. Starch gelatinisation began near the outer surface after 1.5 min of cooking and was complete by 2.5 min. During the second cooking phase the thermal energy absorbed was used to evaporate water. When immersion in boiling water was substituted for this second phase of microwave cooking, it took significantly longer for the internal texture to soften adequately for the potatoes to be considered cooked. This suggests that microwave cooking influences texture independently of the thermal profile of the cooking process. Damage by escaping steam is suggested as a mechanism.© 2002 Society of Chemical Industry

Comparison of the Volatile Components of Eight Cultivars of Potato after Microwave Baking

Eight cultivars of potato were baked in a microwave oven. The flavour components of the flesh were isolated by headspace trapping onto Tenax and analysed by gas chromatography–mass spectrometry. Lipid degradation and the Maillard reaction and/or sugar degradation were the main sources of the 80 flavour components identified. It is suggested that total levels of compounds and variations among their profiles may be attributed to differences in activities of lipid enzymes and levels of flavour precursors in the range of cultivars investigated.

Effects of Susceptor, Coating and Conventional Browning Applications on Color and Crust Formation During Microwave Baking

The effects of different browning treatments on the crust color and crust hardness of microwave baked breads were investigated. Microwave oven was operated at 20%, 30% and 40% powers for 3.5–5.5 minutes. As a control, breads were baked in a conventional oven at 200°C for 12 minutes. After microwave baking, breads were browned or conventional browning times increased, crust hardness and weight loss of breads increased. When susceptors were used, desired browning and hardness were obtained on the bottom surfaces of the breads. However, they did not affect top surface color significantly. The optimum microwave baking conditions for safety susceptor and standard susceptor were found as 5.0 minutes at 20% power and 4.5 minutes at 20% power, respectively. Breads coated with a solution composed of 10.5% sodium bicarbonate, 31.6% glucose, 5.3% glycine and 52.6% water (by weight) did not have the desired crust color and hardness. Conventional browning at 200°C for 8 minutes was an alternative to achieve browning on top and bottom surfaces and crust formation on the bottom surface.

Alpha-amylase inhibitor changes during processing of sweet potato and taro tubers.

Alpha-amylase inhibitor changes during processing of sweet potatoes (Ipomoea batatas) and taro (Colocasia esculenta) indicated that varietal differences profoundly influence the thermal inactivation profile. The alpha-amylase inhibitors of taro were almost totally inactivated during oven drying of the chips at 90 degrees C and 100 degrees C for 24 h, while 0.8-10% activity was retained in sweet potato chips under the same conditions. Relatively better thermal stability was exhibited by the sweet potato amylase inhibitors at lower temperatures (70 and 80 degrees C) as well. Cooking by boiling the tuber pieces in water resulted in retention of 29-59% amylase inhibitor in sweet potato and 11-16% in taro. Microwave baking was a better method for inactivation of amylase inhibitors in these tubers. Flour prepared from the tubers retained only trivial amounts of the inhibitor.

Effects of microwave on the drying, checking and mechanical strength of baked biscuits

The influence of high-frequency radiation on quality in terms of checking and mechanical strength of low-moisture baked products was investigated. Biscuits baked in a convection, reel oven were compared to biscuits of very similar moisture content and appearance that were baked in the same oven until the falling-rate drying period but then immediately microwaved for 30 s in a 700 W microwave oven. Microwave baking was found to significantly reduce checking to 5% compared to 61% in conventional biscuits. The average breaking stress required for intact microwaved biscuits two weeks after baking was 997 kPa, while that for conventional samples was 610 kPa. The structure of conventional biscuits was generally found to weaken at a faster rate than microwaved biscuits. Microwaved biscuits were also found to be less susceptible to checking upon exposure to high ambient humidity. In addition, the finite element software, FIDAP, was used to predict heat and mass transfer with respect to time and position during microwaving under various conditions. A biscuit was modeled as an axisymmetric short cylinder. Simulations confirmed greater drying rates and more uniform internal moisture profiles for microwaved biscuits. A minimum microwaving time of approximately 28 s was predicted to be necessary to produce a uniform moisture profile for a power absorption of 1.7 W/g. An elevation in the biscuit temperature during baking as well as a more uniform moisture distribution found in microwaved biscuits were thought to be critical factors in determining checking behavior and mechanical strength.

A review on microwave baking of foods

Summary Microwaves interact with polar molecules and charged particles of food to generate heat. There are differences between the heating mechanisms of microwave and conventional heating. The use of microwave heating has the advantage of saving energy and time, improving both nutritional quality and acceptability of some foods by consumers. Microwave ovens are successfully used both in homes and in the food service industry. However, there are still problems in perfecting microwave baking, therefore it is a popular research area. The main problems found to occur in microwave‐baked food products are low volume, tough or firm texture, lack of browning and flavour development. Recent studies aim to improve the quality of microwave‐baked products. This article reviews the basic principles of microwave baking, problems commonly occurring in microwave‐baked products and finally studies published concerning microwave‐baked products.

Porous starch-based drug delivery systems processed by a microwave route

A new simple processing route to produce starch-based porous materials was developed based on a microwave baking methodology. This innovative processing route was used to obtain non-loaded controls and loaded drug delivery carriers, incorporating a non-steroid anti-inflammatory agent. This bioactive agent was selected as model drug with expectations that the developed methodology might be used for other drugs and growth factors. The prepared systems were characterized by 1H and 13C NMR spectroscopy which allow the study of the interactions between the starch-based materials and the processing components, i.e. the blowing agents. The porosity of the prepared materials was estimated by measuring their apparent density and studied by comparing drug-loaded and non-loaded carriers. The behaviour of the porous structures, while immersed in aqueous media, was studied in terms of swelling and degradation, being intimately related to their porosity. Finally, in vitro drug release studies were performed showing a clear burst effect, followed by a slow controlled release of the drug over several days (up to 10 days).

Optimization of microwave baking of model layer cakes

Response surface methodology was used to optimize the formulation of microwave-baked cakes. The independent variables were water content, emulsifier content baking time, oven power, shortening content and starch type. The quality factors evaluated were specific gravity of batter and volume index, uniformity index and tenderness of the crumb. Constraints for quality factors were obtained by conventional baking of American Association of Cereal Chemists high-ratio cake formulation. Multiple contour plots showed the optimum region for various water and shortening combinations at different emulsifier, time and power levels. Cakes formulated with wheat starch, containing 0.3% polysorbate 60, 133.7% water and 45.2% shortening (flour substitute basis), baked for 6 min at 100% power yielded acceptable cakes that can compete with conventionally baked cakes. Rice and corn cakes had lower quality than conventionally baked high-ratio cakes. Power was found to be the most efficient independent variable affecting all the dependent variables.

Effects of microwave and conventional baking on the oxidative stability and fatty acid composition of puff pastry

AbstractThe effects of microwave and conventional baking on the fatty acid and trans fatty acid compositions of puff pastries, which contain high amounts of hydrogenated fat, were investigated. In addition, free fatty acids, peroxide value, and induction time for oxidative stability by the Rancimat method have been compared for microwave‐ and conventionally baked puff pastries. The data indicate there were considerable changes in acidity, peroxide value, and Rancimat induction time in both microwave‐ and conventionally baked samples. Although the content of saturated fatty acid such as palmitic and stearic and the ratio of saturated to unsaturated fatty acids did not change significantly, an apparent increase was determined in trans oleic acid levels by both baking methods. In addition, a significant decrease in linoleic acid content of the samples was found by microwave baking.

Structural and hydration studies of waxy and mealy potato starch cultivars by deuterium, carbon‐13 CP‐MAS/MASS NMR, and electron microscopy

AbstractProton and deuterium pulsed Nuclear Magnetic Resonance (NMR) techniques were employed to investigate the hydration properties of raw and cooked (steamed, oven baked and microwave baked) waxy (LaSoda and Pontiac) and mealy (Russet Burbank and Norchip) potato cultivars and starches. Three water components (T2Q internal, T2A medium and T2B long component) were resolved in potato cultivars and starches. The first water component T2Q is assigned to the anisotropically bound water within the potato starch granule structure. The T2A corresponds to trapped water, whereas, the T2B‐long component is assigned to the average between weakly bound and free water populations. The anisotropically bound water (T2Q internal) in potato cultivars and starches does not seem to be in fast chemical exchange with free and weakly bound water populations. Well defined powder patterns with a residual deuterium quadrupole splitting of about 1 kHz were observed at 22°C for raw potato cultivars and starches (17%, w/w). The quadrupole splitting, however, disappeared after cooking as a result of heat induced structural changes, and only rapidly, isotropically reorienting water remained. The T2A and T2B values were also significantly affected by the cooking method. The T2B values of cooked potatoes were shorter than those of raw potatoes. Heat induced structural changes were reflected in the shorter T2B value of the cooked and crushed potatoes. Lower average 1H NMR transverse relaxation rates were observed in cooked waxy (LaSoda) in comparison with those of other potatoes.

Effects of Production by Microwave Heating After Conventional Baking on Moisture Gradient and Product Quality of Biscuits (Cookies)

ABSTRACTAfter conventional (forced‐convection heating) baking at 240°C for 4 min, biscuits (cookies) were baked further in a microwave oven at medium and high settings (617.3 and 745.5 W, respectively) to study the effects of microwave baking on the moisture gradient and overall quality of the cookies. Microwave baking significantly (P &lt; 0.05) reduced the moisture gradient and total moisture content of the cookies. Initially, a complete factorial design at baking times of 15, 20, 30, and 40 sec with microwave ovens at high and medium power settings was used to evaluate the moisture gradient and total cookie moisture content. Applying high and medium microwave settings for 30 or 40 sec, respectively, avoided cracking, although the products were slightly darker. Treatment at a high power setting for 20 sec resulted in a moisture gradient of 1.11%/cm and 2.8% cracking. Gradients &gt;1.5%/cm produced significant levels of cracking. Cookies postbaked at a medium microwave power setting for 29 sec produced the same moisture gradient as a high microwave power setting for 23 sec, which was significantly (P &lt; 0.05) lower than the control (cookies baked using the traditional process). The cookies were softer and the color did not differ significantly from that of the control. The expansion ratio of the control sample (11.3) was significantly higher than the combined process sample (10.7), showing a shrinkage effect attributed to the microwave treatment. The removal of the residual moisture during microwaving also increased product weight losses (from 0.912 to 0.956 g).

Polychlorinated Biphenyl Concentration in Raw and Cooked North Atlantic Bluefish (Pomatomus saltatrix) Fillets

Polychlorinated biphenyls (PCBs) were measured before and after fillets of six bluefish (Pomatomus saltatrix) were cooked. Six cooking treatments were used with one fish per treatment. PCB concentrations ranged between 0.114 and 0.748 mg/kg in raw fish and between 0.102 and 0.315 mg/kg in cooked fish. The average for the raw fish was 0.31 and for the cooked fish was 0.19 mg/kg. PCB concentrations in both raw and cooked fillets were well below levels reported for raw fillets from fish tested in the mid-to-late 1980s and FDA health advisories. A decrease in PCB concentration in four of the six cooking treatments was observed. They included, in order of greatest decrease, smoking > microwave > chrabroiling (skin off) > charbroiling (skin on). There was no change with convection oven baking and pan frying. When adjusted for weight loss during cooking, all cooking methods showed PCB loss (average = 46%). The most effective cooking methods for removing PCBs from bluefish included smoking and microwave baking. T...

TEXTURAL AND VISCOELASTIC CHANGES OF CANNED BISCUIT DOUGH DURING MICROWAVE AND CONVENTIONAL BAKING

ABSTRACTTextural changes of canned biscuit wheat dough during microwave and conventional baking were described and contrasted using empirical methods. Drastic increases of specific volume and modulus of elasticity were observed in the beginning and the ending periods of both baking processes. Weight loss showed a significantly (p &lt; 0.001) linear relationship with baking time for both baking methods, but the weight loss rate constant for microwave baking was 0.36%/s significantly (p&lt;0.01) higher than conventional baking. Multi‐dimensional Scaling showed that microwave baking for 50 s best resembles the textural characteristics of wheat dough under conventional baking for 10 min. Stress relaxation modeling indicated that microwave baking produced higher viscosity and modulus of elasticity values which translates into baked biscuits with undesirable tougher texture.

Microwave Baking of Bread

The development of a laboratory microwave thermal baking technique was the focus of this study. A solution to the problem of microwave baking bread in metal baking pans was to cut holes in the sides and bottoms of the pans to allow microwaves to pass through. This improved heating uniformity inside the loaf while the high thermal conductivity of the metal enabled good crust formation. The holes were small enough to retain dough when the pans were lined with baking paper

Mutagenic activity and sensory quality of grilled chickens processed under different conditions

The present study deals with the effect of four different cooking techniques (roasting, grilling, microwave baking and frying with olive oil) on physicochemical parameters (cooking loss, WHC, texture and colour) and lipid oxidation (by TBARS measurement) of foal meat. Thermal treatments induced water loss (P < 0.001), being lower in foal steaks cooked in the grill (25.8%) and higher in foal samples cooked in the microwave (39.5%). As it was expected, all the cooking methods increased TBARS index, since high temperature during cooking seems to cause an increase of the lipid oxidation in foal steaks. Statistical analysis displayed that WHC was affected (P < 0.001) by thermal treatment, since the smallest WHC values were observed in samples from microwave treatment. Thermal treatment also caused a significant (P < 0.001) increase in the force needed to cut the foal steaks. Regarding colour parameter, cooking led to an increase of L*-value (lightness) and b*-value (yellowness), while a*-value (redness) markedly decreased in all samples.

Effect of autoclaving and conventional and microwave baking on the ergot alkaloid and chlorogenic acid contents of morning glory (Ipomoea tricolor Cav. cv.) heavenly blue seeds

The main objective was to measure the stability of Heavently Blue morning glory seed derived ergot alkaloids and chlorogenic acid. A second objective was to measure the protein, amino acid, carbohydrate, fat, mineral, and trypsin inhibitor contents of the seeds