Patent Application
20080145483
Legumes include the pulses and other well-known plants that bear legume fruits including, but not limited, to soybean, lupins, groundnut (such as peanuts) and clover.
Pulses are annual leguminous crops yielding from one to twelve grains or seeds of variable size, shape and color within a pod, harvested solely for dry grain. In accordance with the Food and Agricultural Organization of the United Nations (FAO), 11 primary pulses are recognized: Dry beans, Dry broad beans, Dry peas, Chickpea, Dry cowpea, Pigeon pea, Lentil, Bambara groundnut, Vetch, Lupins, and Minor pulses (Lablab, hyacinth bean (Lablab purpureus), Jack bean (Canavalia ensiformis), sword bean (Canavalia gladiata), Winged bean (Psophocarpus teragonolobus), Velvet bean, cowitch (Mucuna pruriens var. utilis), Yam bean (Pachyrrizus erosus)).
One disadvantage associated with the consumption of dry beans and other pulses, is their long cooking time needed to soften the beans to an edible texture. The loss in cooking quality is associated with the development of hardness in stored dry beans and recognized as the hard-to-cook (HTC) phenomenon. The HTC phenomenon is the result of multiple physiological-chemical mechanisms. High temperatures and high relative humidities accelerate the development of the HTC phenomenon in stored dry beans (Berrios et al., 1998; Berrios et al., 1999). Due to the long cooking time required for cotyledon softening, HTC beans result in increased energy utilization, inferior nutritional quality, and poor acceptance by consumers (Bressani et al., 1963). Efforts to increase the utilization of beans have employed a variety of scientific approaches and processing techniques such as germination, fermentation, dehulling, fractionation, autoclaving, roasting, canning, drum drying and most recently the use of extrusion cooking.
Extrusion is a technology that involves heating a food material and/or food ingredients to relatively high temperature under pressure until it melts, and then releasing it into the ambient atmosphere, causing it to expand and solidify. The resulting product is a shelf-stable convenience, ready-to-eat food. Extrusion cooking offers the advantages of versatile storage options, low production costs, energy efficiency and shorter cooking times (Harper 1981).
Fast cooking using extrusion technology, is an alternative to the long boiling and other traditional forms of cooking legumes.
According to an embodiment of the invention an extrusion process for forming a legume food product with a high expansion ratio is set forth, wherein the expansion ratio is uniform.
According to a further embodiment of the invention, the extruded legume food product may be of various shapes and sizes finding utility in a wide variety of food consumables, ranging from snack foods to breakfast cereals.
“Legumes” include pulses and other well known fruits that bear legume fruits, including, but not limited to soybean, lupins, groundnut (such as peanuts) and clover.
“Pulses” refers to annual leguminous crops yielding from one to twelve grains or seeds of variable size, shape and color within a pod, harvested solely for dry grain.
“Extrusion” is a high temperature, high pressure, short time process that transforms a variety of food raw materials and ingredients into modified intermediate and finish products.
“Melt” refers to the molten extrudate.
“Extrudate” refers to the product obtained through extrusion processing.
“Supercritical fluid extrusion” involves the coupling of supercritical fluids, particularly supercritical carbon dioxide, and extrusion processing.
“Co-extrusion processing” refers to a technique where of two or more different yet compatible foods and/or food ingredients are combined in an extrusion die. The food materials can come from two extruders or from an extruder and a pump. This process permits to make specific products; such as, products with two or more different textures or colors or flavors.
“Preconditioner” is an atmospheric or pressurized chamber in which raw granular foods and/or food ingredients are uniformly moistened or heated or both by contact with water or live steam before entering the extruder.
“Shelf stable” refers to the length of time that corresponds to a tolerable loss in quality of processed foods and other perishable items.
“Flashing” refers to the sudden evaporation of moisture that occurred at the extruder die end, when superheated water is suddenly exposed to ambient conditions.
“Expansion” relates to the physical transformation which is observed when pressurized, molten flour or melt is suddenly exposed to ambient conditions.
“Expansion Ratio” (ER), also referred as Sectional Expansion Index (SEI) and Radial Expansion Ratio (ER)radial, is expressed as the ratio between the cross-sectional area of the extrudate and the area of the die or as the ratio between the diameter of the extrudate and the die.
“Uniform expansion ratio” (UER) is defined as a condition in which the variation of the expansion ratio for randomly selected portions of an extruded rod is less than 20% of the mean expansion ratio, and variations in expansion ratios among different batches of the product produced with the same ingredients under the same process condition are less than 20% of the mean expansion ratio.
“Expansion Indexes” (EI) refers to the overall expansion of an extrudate that takes place in three dimensions i.e. cross sectional, longitudinal, and volumetric expansion. They are defined by the mathematical equation: VEI=SEI×LEI, where SEI is sectional expansion index, which characterized diametral expansion; LEI is longitudinal expansion index and VEI is volumetric or overall expansion index.
“Expansion parameters” include, but are not limited to, expansion and density.
“Density” by definition is mass per unit volume, expressed by the mathematical equation, ρ=m/V, where p is density, m is mass (kg), and V is volume (m3).
“Product density” (D) refers to the measure of extrudate mass per unit of volume. The higher an extrudate density, the higher it's mass per volume.
“Water solubility index” (WSI) of an extruded product describes its solubility in water. The value is given as a percent on a dry weight basis, and is described by the mathematical equation, WSI=[(mass of dissolved solid in supematant)/(mass of dry solids)]*100
“Water absorption index” (WAI) of an extruded product describes its ability to absorb water. The value is given as a percent on a dry weight basis, and is described by the mathematical equation, WAI=[(mass of sediment)/(mass of dry solids)]*100
“Texture properties” of a food are that group of physical characteristics that arise from the structural elements of the food, are sensed by the feeling of touch, are related to the deformation, disintegration, and flow of the food under a force, and are measured objectively by functions of pressure, time, and distance. They include, but are not limited to, hardness, strength, mouthfeel and viscosity.
“Hardness” is a mechanical property of a material that characterizes its resistance to deformation. Therefore, hardness of an extruded product describes the amount of force needed to cause deformation.
“Strength” is most often used to describe a material's Yield Strength. Yield Strength is a mechanical property of a material that characterizes its resistance to deformation. Therefore, strength of an extruded product describes the amount of force needed to cause deformation.
“Lightness” is synonymous with brightness, which indicates the brightness or darkness of a color. A low lightness value indicates dark (black), while a high lightness value indicates bright (white).
“Hydration properties” include, but are not limited to, the water solubility index (WSI) and the water absorption index (WAI).
“In vitro protein digestibility” (IVPD) refers to observation made experimentally in the test-tube, as distinct from the natural living conditions, in vivo. IVPD is generally expressed as the percent of protein hydrolyzed by digestive proteolytic enzymes.
“Consumer tasting”, referred also as “Hedonic scale”, involves having potential consumers of a product evaluate various products and a small number of items on a ballot.
“Fortification” is the addition of nutrients in amounts significant enough to render the food a good to superior source of the added nutrients. This may include addition of nutrients not normally associated with the food or addition to levels above that present in the unprocessed food.
“Glycemic Index” is a physiological measurement of carbohydrate quality, based on their immediate effects on blood-glucose levels. Glycemic index (GI) uses a scale of 0-100. Pure glucose serves as a reference point and is given a GI of 100. When Carbohydrates in foods are compared gram for gram, GI values of 55 or less are considered low GI foods, GI values from 55-69 are considered intermediate GI foods and those with GI 70 or more as high GI foods.
“Starch” refers to a carbohydrate polymer occurring in granular form certain plant species notably cereals, tubers, and pulses such as corn, wheat, rice, tapioca potato, pea etc. The polymer consists of linked anhydro-a-D-glucose units. It may have either a mainly linear structure (amylose) or a branched structure (amylopectin). The molecular weight of the constituent polymers, particularly amylose, varies between different starch sources. A single plant species may exist as hybrids with various proportions of amylose and amylopectin e.g. high amylose corn.
“Specialty Starch(es) or Starch Derivatives” a generic term for all products produced from native starch including modified starches and starch hydrolysis products. They are used to improve the processing, physical and chemical attributes and eating qualities of the food products and may also address nutritional needs, such as fiber in the diet.
“Decorticated” refers to the removal of the surface layer, bark, husk, membrane, or fibrous cover of a seed or grain.
“Particle size” refers to particles from flours and/or powders that have been sized to a particular dimension through standard size designed sieves or screens.
“Sieving” refers to a method for categorizing a flour's and/or powder's particle size by running them through standard size designed sieves or screens.
“Legume based flours and/or powders” refers to a mix containing legume flour and plant (legume, cereal, fruit and vegetables, tubers) material and/or their ingredients (starch, dietary fibers, pigments, flavor extracts, phytonutrients) and/or animal (dairy, other) material and/or their ingredients (protein, sugar, fat, flavor extracts, other) and/or microbial based ingredients (protein, dietary fibers, vitamins, minerals, other) and/or other conventional and non-conventional food grade ingredients (specialty starches, water and oil soluble vitamins, minerals, colors, flavors, other).
“Microbial fiber” refers to dietary fiber such as beta-1,3 glucan from nutritional yeast, which is grown specifically for its nutritive value.
The technical and practical constraints for the production of expanded legume based extrudates fall into two separate categories. The first category relates to the parameters of the extrusion process itself. These are controllable physical/structural factors such as moisture content and particle size of the extrusion feed, barrel temperature and pressure, and residence time, which have direct effect on the quality attributes of the extrudate, such as, expansion ratio, nutritional value, density, color, water solubility/absorption, and its textural properties. The second category pertains to the use of legume flours and/or powders and legume based flours and/or powders with functional food additives, which have direct effect on the healthful, sensorial and textural characteristics and appearance of the final extrudate. If the problems identified above could be properly addressed and resolved, pulses could be used in making highly nutritious, healthful and convenient ready-to-eat expanded extruded and co-extruded products.
An embodiment of the invention describes particular extrusion processing parameters applied to extruded legume flours and/or powders in a way that results in uniformly highly expanded, crispy, tasty and shelf-stable extrudates. A further embodiment is the use of sieved formulations containing additives and/or food ingredients from plant and animal sources such as, but not limited to, cereals, legumes and dairy proteins; specialty starches; fruits, vegetables and grain-based fibers; microbial based ingredients such as protein, dietary fiber, vitamins and minerals; texture and flavor modifiers including emulsifiers; colors, water and oil soluble vitamins and minerals, and spices mixed at specific ratios, which result in commercial type, highly nutritious, convenient and appealing expanded snack and breakfast cereal-type products of different shapes and sizes. Dietary fiber typically suggests a plant derived indigestible complex carbohydrate categorized as either water soluble or water insoluble; however, in accordance with an embodiment of the invention the indigestible carbohydrate may also be drawn from a microbial source, such as nutritional yeast.
Another embodiment of the invention is the use of the expanded extrudate as ingredients in, but not limited to, bakery products, confectionary products and nutraceuticals of different shapes and sizes. The shapes that can be obtained are consistent with those desired by one of skill in the art such as bars, rods, balls, curls and other shapes of varying sizes.
A further embodiment of the invention is the use of legume flours and/or powders and legume based flours and/or powders to form the extrudate. Legumes, which may be utilized, include but are not limited to dry beans (Phaseolus spp.), lentil (Lens culinaris), dry peas (Pisum spp.), chickpea or garbanzo (Cicer arietinum), soybean (Glycine max), broad bean (Vicia faba), dry cowpea or black-eyed pea (Vigna sinensis; Dolichos sinensis), pigeon pea, cajan pea or Congo bean (Cajanus cajan), bambara groundnut or earth pea (Voandzeia subterranea), spring/common vetch (Vicia sativa), lupins (Lupinus spp.), and minor pulses/pulses including: Lablab, hyacinth bean (Lablab purpureus), Jack bean (Canavalia ensiformis), sword bean (Canavalia gladiata), Winged bean (Psophocarpus teragonolobus), Velvet bean, cowitch (Mucuna pruriens var. utilis), Yam bean (Pachyrrizus erosus), guar bean (Cyamopsis tetragonoloba).
Additionally, raw legume seeds may be utilized, wherein the seeds are singularly or in combination, whole, split or decorticated.
A further embodiment of the invention is the use of flavorings, coatings or colors The flavorings or coatings that may be utilized are inclusive of those routinely available to one of skill in the art, which include formulations of solids, pastes or liquids as well as natural or synthetic flavorings. The color of the extrudate may be enhanced or changed using natural or synthetic colors, readily available to one of skill in the art.
Expansion relates to the physical transformation which is observed when molten flour (or “melt”), under high temperature and pressure, is suddenly exposed to ambient temperature and pressure. As the melt exits the extruder die, the sudden decrease in temperature and pressure causes the near-instantaneous expansion of the molten flour, which is also accompanied by extensive flushing or loss of moisture from the extruded product. The expansion of the extrudate, is one of the most important characteristics of interest for the snack food industry. (Mercier et al, 1989). There is limited information about expansion characteristics of legumes, since there is a conception that legumes' flours do not expand well. For this reason, legume flours and/or powders have not been used to produce expanded snacks and this type of products are made exclusively from mayor cereal grains (eg., corn, wheat and rice) and their starch-based flours were values greater than 20 have been obtained (Colonna et al., 1989; Meuser et al., 1894; Barret and Kaletunc, 1998). Soy protein with added starch has also been used for this purpose, but mainly for the fabrication of pet foods. Expansion is directly related to the moisture content of the feed, die temperature and pressure. Moreover, the particle size of the feed and extruder screw speed (Conway, 1971), as well as the presence of specific food ingredients in the formulation, have an important effect on the expansion and texture of the final extrudate. By properly selecting the above extrusion processing parameters and ingredients, it is possible to obtain desirable expansion, texture, nutritional value, color, and shelf stability in the finished product. Below is a discussion of how this is achieved by an embodiment of the invention.
According to an embodiment of the invention, as well as a highly expanded legume product, possessing expansion ratios of 6 or greater, the legume product is also uniform with regard to the expansion ratio. A uniform expansion ratio (UER) creates a uniform texture, which is an important and desired feature in food products, especially those products which may have additional coatings or flavorings added; moreover, a uniform expansion ratio ensures that the texture will be consistent within each batch processing of the extruded legume product. Table 13 demonstrates the uniform expansion ratio that can be achieved by an embodiment of the invention.
1Control
2Rods
3Balls
4Diameter
5Var
4Diameter
5Var
4Diameter
5Var
6ER
6ER
6ER
1Control: Extrudate from 100 garbanzo flour
2Rods: Extrudate from garbanzo based formulation in the form of rods
3Balls: Extrudate from garbanzo based formulation in the form of balls
4Diameter (mm): Each diameter value in the table represent the average of five randomly measures on rod and ball extrudates
5Var (%): Percent variability = 100 − [(diameter value/maximum diameter value of 125 values) * 100]
6ER: Expansion Ratio of the extrudate
A certain amount of moisture is necessary in order to permit proper cooking and promote expansion of the extrudate (Chen et al. 1991, Gujska and Khan, 1990, Balandran et al, 1998). We determined the effect of moisture and die temperature on expansion characteristics, such as diameter and expansion ration, of lentil, dry peas and garbanzo bean extrudates. As observed in
Proper expansion of the extrudate at low moisture content, typically 4 to 6% on dry basis, is desirable for the production of ready-to-eat snacks and breakfast cereal type products. Further drying may be necessary to bring the moisture to the above level for more moist extrudates to achieve proper texture, while maintaining the shelf stability of the final expanded extruded product.
Pressure in the extruder is a function of die restriction, temperature build up along the length of the extruder barrel, and compression caused by the screw. Pressure is created when pulses-based flour is fed into the extruder and gets mixed with water and other additives to become plasticized dough, which is progressively cooked, while moving at high speed along the externally heated barrel sections of the extruder. The steam formation caused by the combined effect of moisture and temperature have a direct effect on die pressure. An important role of pressure on the product under extrusion is its direct effect on mass viscosity of the melt. The surface response plot shown in
The effect of extrusion processing parameters of die temperature of 160 and 180° C. and moisture addition of 28, 24, and 20% on the proximate composition of lentil flours is presented in
Moisture content also has an impact on the concentration of nutritional components in the extrudate, such protein and ash. Lentils extruded with moisture addition in the range of 28 to 20%, demonstrated crude protein values of 11.46 and 12.71% at extruder die temperatures of 160 and 180° C., respectively. In general, the higher values in crude protein content were indirectly proportional to die temperatures and directly proportional to the feed moisture. Total ash (minerals) values showed only a minor increase with a reduction in moisture content in the extrudate and an increase in die temperature of the process. A similar pattern on proximate composition values was observed for dry peas and garbanzo extrudates. This indicated that the extrusion processing parameters of moisture and temperature studied, had a direct effect on the nutrient compositional values of the final extrudate. Total carbohydrate values, which were calculated by difference, varied according to the variation on proximate composition values of the analyzed nutrients from 46.83 to 67.33%.
Moisture content of the melt is critical since it relates both to how much the extrudate will expand when it exits the extruder, as well as to the shelf life of the finished product. Moreover, moisture content of the extrusion product is important because it has an effect on both the shelf life of the product as well as consumer acceptance.
Water activity (aw) predicts stability of foods and food ingredients with respect to physical properties, microbial growth and rates of deteriorative reactions. The latest, play a significant role in determining the activity of enzymes and vitamins in foods and can have a major impact their color, taste, and aroma. Therefore, control of aw, rather than water content, is very important in the food industry as low aw presents stability of food materials under storage (increasing shelf life). Additionally, aw causes large changes in textural characteristics in the food material such as crispness and crunchiness (e.g. the sound produced by ‘crunching’ breakfast cereals and expanded snacks disappearing about aw≧0.65). In general Processed Foods have a aw of 0.72-0.80 with a moisture content of about 15% and Dehydrated Foods have a aw≦0.4 with a moisture content of about 5%. The absolute limit of microbial growth is about aw=0.6.
Most commercial extruded cereal-based snacks have final moisture content in the range of 4 to 6% with aw≦0.4. However, in our study with legume extrudates, we found that extrudates with a moisture content between 9-11% had an aw in the range of 0.30-0.44, which fell within the range of shelf stable product. The extrudates remained shelf stable and with good texture (dry and crispy) and appearance for up to 1 year.
For plant-based foods, legumes are relatively high in protein content. The exposure of proteins to high extrusion cooking temperatures may cause denaturation and other changes in the protein structure and/or to protein-protein interaction (Stanley, 1989; Phillips, 1988; Li et al. 2000). These physical changes in the protein structure results in a more digestible protein when consumed as a food. Cooking temperature, time and pressure of extrusion play important role in the protein's denaturation process.
The values of in vitro protein digestibility of the control (non-extruded) samples were 80.69, 79.86, and 75.63% for lentils, dry pea, and garbanzo flours, respectively. FIG. 6 presents the results of in vitro protein digestibility of the three extruded legumes. In general, exposure of high protein legume flours to a high-temperature-short-time extrusion process demonstrated to improve the in vitro protein digestibility of the resulted extrudates. Additionally, the extruded parameter of moisture addition had a more significant effect (P≦0.05) than temperature on increasing the in vitro protein digestibility of the extruded legume flours under the conditions of this study. Dry pea extrudate demonstrated the higher values on in vitro protein digestibility, followed by lentil and garbanzo extrudates. Extrusion processing parameters effect on color of the extrudate
One of the effects of extrusion cooking is the change in color of the lentil extrudates.
The Color index (ΔE) is an evaluation of the total color difference between the sample and control or standard by taking into consideration the color parameters L* a b*. ΔE indicates the size of the color difference but not in what way the colors are different. The response surface graph (
Specific mechanical energy (SME) reflects the amount of energy generated in the process of extruded pulses. The surface plot of SME as effect of moisture content of the feed and die temperature showed that the specific mechanical energy increased as the feed moisture was reduced from 28 to 20% (
To evaluate the effect of particle size and extruder screw speed on the expansion of legumes, black beans were ground using a Hammer Mill equipped with 0.85, 1.15, 1.53, and 2.28 mm stainless steel sieves and a Pin Mill to produce bean flours with different particle sizes. Pin Mill produced the finest flour. The extruder screw speeds used to process the flours were 400, 450 and 500 rpm, and the die temperature was 160° C. The flours were metered into the extruder feed port at a rate of 25 kg h−1 and water was supplied to the extruder using a variable piston pump (Model P5-120, Bran and Luebbe, Wheeling, Ill.) to give a final feed moisture content of 18% (wwb).
Table 1 summarizes the average values with their corresponding standard deviations of percent torque and expansion ratio of the bean flours extruded under the different particle sizes and screw speeds studied. Percent torque and expansion ratio, within the different particle sizes evaluated, increased with an increase in screw speed. Greater expansion of extruded material is related to crispiness and therefore it is considered as a desirable attribute in the fabrication of snacks and ready to eat (RTE) foods. The fine Pin milled flours extruded at 500 rpm demonstrated the greater expansion in this study, which represented an expansion ratio of 6.74±0.86.
Variation of cutter blade speed produced extrudates with distinct shapes. At cutter speed of about 500 rpm the extrudate was in the form of cylindrical rods were at a higher speed of about 2,000 rpm it was in the form balls or spherical shaped product (
The taste testing of the extruded in the form of rods and balls was done to compare their sensory attributes. The results were as given in Table 3. It was observed that the sensory attributes evaluated for the two extruded products were not significantly different from each other. In spite of their different shape, the panelists gave the same score for flavor, color, texture and taste to both products indicating that they were considered equally acceptable.
ns= not significant.
1= only for ball shaped product.
Decorticated Red Chief lentils (Lens culinaris L.) were obtained from Moscow Idaho Seed Co., Moscow, Id. Prior to milling, each lot of seeds was mixed to a uniform lot. For the production of flours, the homogenized lentils were ground in a hammer mill using a 1 mm screen. The lentil flower was mixed with apple fiber, high amylose corn starch and flavoring ingredients (Table 4).
A Clextral Evolum HT 32H twin-screw extrusion system (Clextral-Bivis, Firminy Cedex, France) was used in this study. The heating profiles for the six barrel sections of the extruder were 15, 80, 100, 120, 140, and 160° C., respectively. Flours were fed into the extruder feed port by a twin-screw, lost-in-weight gravimetric feeder (Model LWFD5-20, K-Tron Corporation, Pitman, N.J.) at a rate of 25 kg/h and the extruder was run at three screw speeds of 500, 600 and 700 rpm. Water was added into the extruder through a variable piston pump (Model P5-120, Bran and Luebbe, Wheeling, Ill.) to bring the moisture contend of the feed under extrusion to 15% (wwb). When the processing conditions of torque and temperature were at steady state the extrudates, coming out of 2 circular dies 3 mm in diameter, were collected for 5 min.
The extrudates in the form of rods or flours were used to evaluate the effect of screw speed and starch sources on various physical characteristics of the product.
(EI). A digital caliper with an accuracy of ±0.01 mm was used to measure the cross sectional diameter (mm) of extrudates when the extrudates reached ambient temperature. The average value of twenty measurements for the random profiles of the same section was recorded. Expansion index was calculated as expressed as the ratio between the cross-sectional area of the extrudate and the area of the die orifice.
Product density (D). The mass of ten pieces of extrudates was measured with an accuracy of ±0.0001 g. The lengths and mean diameters of the samples were measured with the digital caliper. The density of extrudate that was assumed to be cylindrical shape in this study was calculated by the following equation:
where D is the density of extrudates (kg/m3); M is the mass of the extrudate (g); and h is the length of the extrudate (mm); d is the mean diameter from three measurements of the extrudate (mm).
Water solubility index (WSI) and water absorption index (WAI) were determined with the use of the method described by Jin et al. (1995) with minor modifications. The extrudates were ground through an Udy cyclone mill (Fort Collins, Colo.) with a 0.5 mm screen. A two-gram sample was dispersed into 20-mL distilled water at 25° C. The suspension in a weighted centrifuge tube was stirred vigorously on a vortex mixer for 5 sec. The tube was then kept still for 10 min and stirred for 5 sec every 5 min. The suspension was centrifuged at 3000×g for 10 min and then decanted to determine solid content in the supernatant and weigh the sediment. WSI (%) and WAI (%) were calculated as follows:
WSI (%)=100×(Weight of dissolved solids in supernant)/(Weight of dry solids)
WAI (%)=100×(Weight of sediment)/(Weight of dry solids) (3)
Rapid viscosity analysis (RVA). The results of RVA demonstrate the changes in viscosity over a time-temperature profile, which reflects the molecular weight and conformation of starches. RVA for Red Chief lentil flours and four starches was conducted through a Rapid Visco-Analyser (RVA3d, Newport Scientific, Sydney, Australia) after a sample of 3.00 g (d.b) dissolved into 25.00 g distilled water completely. All samples were subjected to a time-temperature profile described as follows. The samples were first kept equilibration at 50° C. for 2 min, and then were ramped to 95° C. within 9 min and held at 95° C. for 15 min. The samples were in turn cooled down to 50° C. within 9 min and held at 50° C. for 10 min. The viscosity of samples was expressed as rapid viscosity units (RVU).
The parameters that were useful to describe to change of viscosity were recorded during measurement. Peak viscosity and peak time indicated the maximum viscosity during pasting and the time when the peak viscosity appears, respectively. Holding strength and breakdown viscosity showed the holding viscosity after the peak viscosity and the difference between the peak viscosity and the minimum viscosity during pasting, respectively. Setback demonstrated the difference between the maximum viscosity during cooling and the minimum viscosity during pasting; and final viscosity indicated the viscosity of the suspensions at the end of the RVA run (45 min). All measurements were performed in triplicate.
Texture analysis. A TA-XT2 texture analyzer (Stable Micro Systems, Surrey, England) was used to measure the texture of a cylindrical extrudate sample with a length of 10 mm at ambient temperature. A cylinder aluminum probe with a diameter of 50 mm was used to press the sample against a flat plate fixed on the loading frame to 50% of its original length at a speed of 0.5 mm/s. The corresponding force-time curve was recorded and analyzed by a computer program (Texture Expert Exceed, Stable Micro Systems, Surrey, England) simultaneously. The force was recorded in gram and converted to Newton for the calculation of hardness and strength. The hardness of samples was defined as the peak value of the compression force. The sample strength was calculated by the following equation:
where S is the strength (N.mm−2), Ac is the area under time-force curve (N.t), Ap is the original across-sectional area of the extrudates (mm−2) and t is the time that the probe compresses on the extrudate. Ten replications were performed to complete this calculation.
Statistical analysis. All the values of averages, standard deviations and correlations were calculated using Microsoft Excel software (Version 2002). Correlation between the physical parameters studied, were from pool values of extrudates with and without starch addition. The determination of ANOVA was performed using SAS 8.1 software (SAS, 1999) with a significant level of 5%.
Effect of starch and fiber on the physicochemical properties of extrudates: The expansion, texture and hydration properties of the control lentil extrudate and those lentil extrudates with apple fiber and flavoring ingredients and with or without starch sources, processed at extruder screw speed of 600 rpm are shown in
Expansion:
EI of the lentil extrudate with high amylose corn starch (Hylon V) addition was slightly higher than the lentil exudates with potato starch source. It has been reported that the EI of potato flour was lower than that of corn flour, processed at the same extrusion conditions (Onwulata et al., 2001b). This could be explained as follows: (1) the gelatinization temperature of potato starch (56-66° C.) is known to be lower than that of corn starch (62-72° C.); the relatively low gelatinization temperature means that potato starch exhibits high melting viscosity and early melt during extrusion (Della Valle et al. 1995; Sigh et al, 2002); (2) potato starch has more phosphate cross-linkages in the amylopectin also attribute to the relatively high initial viscosity (Eerlingen et al., 1997) and low expansion during extrusion.
Density: The density of the lentil extrudate without apple fiber addition was significantly (P<0.05) smaller than the lentil extrudates with apple fiber. Among the lentil extrudates with apple fiber and starch addition, the one with high amylose corn starch (Hylon V) had the lowest density followed by the one with modified potato starch (PB800). The highest density was observed for lentil extrudates with PP40, PC10 and lentil extrudate without starch addition (
Hardness and strength: As shown in
Hydration properties of extrudates:
Properties of starch and lentil flours: Table 5 shows the RVA and the hydration properties for the lentil extrudates formulated with corn and potato starches and the control extruded lentil flour. As indicated in Table 2, the extruded lentil flours formulated with PP40 (pregelatinized potato starch) and PC10 (native potato starch) exhibited significantly (P<0.05) the highest values of peak viscosity, holding strength, breakdown and final viscosity and setback than those formulated with others starch sources and the control. Additionally, extruded lentil flours formulated with Hylon V (high amylose corn starch) exhibited significantly (P<0.05) the lowest values of the RVA parameters of the studied starches.
Table 5, also shows that the different starch sources had great influence on the WAI and WSI of the lentil based extrudates. The highest value of WAI was observed for the extruded lentil flours formulated with PP40 starch and the lowest for the lentil flours. With respect to WSI, the highest (P<0.05) value was observed for the extruded lentil flour. The extruded lentil flours formulated with the various starches were not significantly different (P<0.05) among themselves.
The correlation between the RVA and hydration properties with other physical parameters of lentil extrudates studied is shown in Table 6. Among the RVA parameters, setback had a significant negative correlation with expansion and a positive correlation with density of the extrudates. The correlation between the stated physical properties of the extrudates among all other samples varied randomly and was lower than the one previously observed for setback.
Based on the result of the physicochemical evaluation of the extrudates described above, we determined the effect of different extruder screw speeds on the physicochemical properties of the lentil extrudate with Hylon V starch and apple fiber.
Screw speed and physicochemical properties of extrudates: The effects of screw speed on the physicochemical properties of the lentil extrudate with hylon V starch and apple fiber are shown in
Expansion Index: As shown in
Density:
The Hardness and strength:
WSI and WAI: As observed with the expansion parameter (
Lentil beans (Lens esculenta), garbanzo beans (Cicer arientinum L.), whole yellow dry peas, and split-decorticated yellow dry peas (Pisum sativum) with moisture content of 9.2, 8.6, 9.6, and 10.1% (wb), respectively, were individually mixed to uniform lots and ground to flour using a Pin Mill model 160Z (Alpine, Co. Augsburg, Germany). Sodium bicarbonate (Sigma Chemical Co. St. Louis, Mo.) and starch Hylon V (National Starch & Chemical, Bridgewater, N.J.) were added to flours at 0.4% and 20% (w/w), respectively (Table 7). The flours with added ingredients were mixed for 10 min using a large Hobart mixer Model V-1401 (The Hobart Mfg. Co., Troy, Ohio) before extrusion processing. Totally 2,000 lbs of legume seeds and 350 lbs of starch were used in this comprehensive extrusion experiment.
1Leavening agent (LA): sodium bicarbonate.
2Starch (St): Hylon V, a high amylase corn starch.
3Split pea: Split and decorticated dry pea.
A twin-screw extruder (Continua 37, Werner and Pfleiderer Corp., Ramsey, N.J.) system was used to process the legume flours. The extruder had eight barrel sections, each with a length of 160 mm. The screw diameter was 37 mm and the total configured screw length was 1,321 mm, which gave an overall L/D ratio of 35.7. Each barrel section was heated by separate hot oil recirculating systems (Model MK4X06-TI, Mokon Div., Protective Closures Co., Inc., Buffalo, N.Y.). The heating profile used in this study was: no heat, 60, 80 100, 100, 120, 140, and 160° C. corresponding to barrel sections 1 to 8, respectively. Screws were driven by an 11.2 kW variable speed DC drive (Model DC300, General Electric Co., Erie, Pa.) operated at 500 rpm. The entire system was controlled by a programmable controller (Series One Plus, General Electric Co., Charlottesville, Va.). Flour was metered into the feed port by a twin-screw, lost-in-weight gravimetric feeder (Model LWFD5-20. K-Tron Corp., Pitman, N.J.) at a rate of 25 kg h−1 (wwb), and water was supplied to the extruder using a variable piston pump (Model P5-120, Bran and Luebbe, Wheeling, Ill.) to give a final moisture content of 15% (wwb) to the feed solids. Legume flours were extruded trough a die containing two circular openings 3.5 mm in diameter. A computer collected extruder parameters' data at a 1 s intervals for a total of 5 min, using LabView data acquisition system version 5.0 (National Instruments, Austin, Tex.). Data were collected approximately 5 min after the operation conditions of torque and pressure were at steady state.
Cross sectional diameter was measured with a digital caliper in mm at two random places on the extruded material, without cutting, in the form of rods coming out of the extruder die. A total of 20 measurements were made per each extrusion run and the expansion ratio of the legume extrudate (rods) was calculated by dividing the cross sectional area of the extrudates by the cross sectional area of the 3.5 mm die orifices. After measurements, the extruded material was collected in large plastic bags placed in 20 gal plastic cans, cooled down to room temperature, and weighed before stored at refrigeration temperature for subsequent sample preparation and analyses.
Diameter and expansion of extrudates: The average data of diameter and expansion ration of the extrudates is presented in Table 8. The average diameter data was directly proportional to the average expansion ratio data. This was because the calculation of expansion ratio depended on the radio of the diameter of the extrudate. In general the expansion ratio was highest for split pea and lowest for garbanzo extrudates. In increasing order of magnitude, the expansion ratio of the legume extrudates was as followed: split pea>whole pea>lentil>garbanzo.
1Mean and standard deviation of 20 measurements
2Leavening agent (LA): sodium bicarbonate added at 0.4% (w/w).
3Starch (St): Hylon V added at 20% (w/w).
4Split pea: Split and decorticated dry pea.
The addition of high amylose corn starch to the legume flours increased the expansion ratio in 2.75, 1.63, 1.32, and 1.17 times for garbanzo beans, lentils, whole peas, and split pea extrudates, respectively. Conversely, the addition of sodium bicarbonate slightly reduced the expansion ratio of the extruded products.
Table 9 represent the effect of the legume extrudates on the extrusion processing parameters of die temperature, die pressure and torque. In general it was observed that the different legumes and legume formulated with leavening agent and/or high amylose corn starch had a highly uniform effect on the studied extrusion processing parameters. Also, it was observed that the torque, generated at consequence of the process, was directly related to the die pressure. The extrusion temperature profile was set to have 160° C. on the last barrel section. However, with the exception of garbanzo extrudates, the values of die temperature for the legume extrudates were above 160° C., regardless of the type of seed or ingredient in the formulation. This indicates that there was additional heat generated during the process, in the form of mechanical heat, as a consequence of shearing and pressure. The die temperature for the different garbanzo extrudates was below 160° C., which indicated that first, there was not additional heat generated during the process of these extudates; and second, that the feed material promoted a small cooling effect on the process. Garbanzo bean contain about 5 percent fat, which was more that double the amount of fat present in the other studied legumes. Therefore, the melting of the fat during processing may have act as a lubricant on the screws promoting less shearing effect. Additionally, the lowest values of torque and die pressure observed for these extrudates further indicate that the lubrication action of the melted fat flowed easier and expanded less that all the other studied legumes.
1Leavening agent (LA): sodium bicarbonate added at 0.4% (w/w).
2Starch (St): Hylon V added at 20% (w/w).
3Split pea: Split and decorticated dry pea.
Decorticated Red Chief lentils (Lens culinaris L.) were obtained from Moscow Idaho Seed Co., Moscow, Id., were homogenized and ground to a fine flour in a Pin Mill. The lentil flour was then formulated according to Table 10.
1A.P.
2W.B.
3PB800
4AP40
5Thermolec
6Yelkin
7Dimo
8Pano
1A.P.: Apple fiber.
2W.B.: Wheat bran.
3PB800: PenBind 800 modified potato starch
4AP40: PenPlus 40 pregelatinized potato starch
5Thermolec: Thermolec lecithin.
6Yelkin: Yelkin TS lecithin.
7Dimo: Dimodan PH 100 K-A
8Pano: Panodan FDP K
A Clextral Evolum HT 32H twin-screw extrusion system (Clextral-Bivis, Firminy Cedex, France) was used in this study. The heating profiles for the six barrel sections of the extruder were 15, 80, 100, 120, 140, and 160° C., respectively. Flours were fed into the extruder feed port at a rate of 25 kg/h and the extruder was run at two screw speeds of 500 and 700 rpm. Water was added into the extruder through a variable piston pump (Model P5-120, Bran and Luebbe, Wheeling, Ill.) to bring the moisture contend of the feed under extrusion to 17% (wwb). When the processing conditions of torque and temperature were at steady state the extrudates, coming out of 2 circular dies 3 mm in diameter, were collected for 5 min.
Result of previous sensory evaluation of legume extrudates indicated that the legume based snacks and breakfast cereal type products have a sticky mouth feeling. This was mainly attributed to their higher protein content.
Therefore texture modifiers (emulsifiers) were used to minimize the unpleasant “sticky” sensory effect in the extrudate and improve their texture and acceptability. The texture modifiers used in the study were Dimodan PH 100 K-A and Panodan FDP K (Danisco Co., Richmond, Ill.) in powder form; Yelkin TS Lecithin and Thermolec Lecithin (ADM Co., Decatur, Ill.) in liquid form. Each of the emulsifiers was used at the following concentrations: 0.25. 0.50, 0.75 and 1.00%.
Preliminary sensory evaluation: Expansion ratio is a leading parameter to consider in the fabrication of expanded snacks of breakfast cereal type products. Therefore, to facilitate the sensory evaluation of the samples, the 32 generated samples were pre-sorted based on their maximum expansion ratio. Sixteen samples were selected, among the 32 generated samples. The expansion ratio of the selected 16 samples varied from 7.99 to 13.60. The first stage of the sensory evaluation consisted in evaluating the pre-sorted 16 samples for expansion, texture, flavor and overall acceptability of the extrudates. The goal of the first evaluation stage was to determine the 4 most acceptable extrudates among the tested emulsifiers. Lentil extrudates, in the form of rods, were cut into 1.25″ length, placed in a pre-coded tray and then evaluated by 19 untrained judges using a score from 1=worst to 5=best.
Table 11 shows the 4 selected lentil based extrudates selected from the first sensory evaluation stage. Results demonstrated that the most acceptable extrudate was that containing Dimodan PH 100 K-A at a concentration of 0.75% and run at 500 rpm. The second and third most acceptable extrudates were those containing Yelkin TS Lecithin at a concentration of 0.75% and run at 500 rpm and Dimodan PH 100 K-A at a concentration of 0.25% and run at 500 rpm, respectively. The least acceptable extrudate of this group was that containing Yelkin TS Lecithin at a concentration of 0.25% and run at 700 rpm. The range of expansion ratio of the selected samples range from 8.75 to 10.24. It was important to notice that when the expansion ratio was in this range, the selection of the best extrudate was mainly due to the type and concentration of the tested emulsifiers.
Based on the result of the first sensory evaluation stage, the 4 selected best samples were further evaluated for a second sensory evaluation stage to select the most acceptable extrudate's containing emulsifier. The sensory evaluation protocol was the same used in the first sensory evaluation stage.
Results of the second sensory evaluation stage demonstrated that the most acceptable extrudate was that containing Dimodan PH 100 K-A at a concentration of 0.75% and run at 500 rpm. The second and third most acceptable extrudates were those containing Dimodan PH 100 K-A at a concentration of 0.25% and run at 500 rpm and Yelkin TS Lecithin at a concentration of 0.25% and run at 700 rpm, respectively. The least acceptable extrudate of this group was that containing Yelkin TS Lecithin at a concentration of 0.75% and run at 500 rpm (
The most acceptable lentil based extrudate from the second sensory evaluation stage containing Dimodan PH 100 K-A at a concentration of 0.25% and run at 500 rpm, was produced in large quantities to be evaluated by large number of potential commercial consumers at a national food festival.
Toasting of extrudates: Toasting operation removes additional moisture from the extrudate, which promote a more crunchy texture to the product. Also, it facilitates the absorption of oil and flavors by the extrudate during the coating process.
In previous studies, we determined that the coating is done more effectively if the extrudate is toasted at 200 to 250° F. In this study, the toasting of lentil based extrudates was conducted in the rotary drum of a coating machine at 200° F. for 5 minutes. It was found that the extrudate lost about 2 percent moisture during the toasting operation (
