WATER AND LIPID ABSORPTION PROPERTIES OF LIGNIN-REDUCED SOY HULLS1,2

Given the nutritional benefits of incorporating lignin-reduced soy hulls into human foods such as restructured pork products, their moisture and lipid absorptive properties were investigated. The effects of three particle sizes, heat, and level of media (water, pork lipid, and water/pork lipid emulsion) were investigated. As particle size increased, water and emulsion absorption generally increased. The fine particle size absorbed less lipids than either of the two larger sizes. An increase in temperature generally increased water absorption, had little effect on emulsion absorption, and no effect on lipid absorption. Water was preferentially absorbed over lipids. Differences in composition enabled lignin-reduced soy hulls to absorb up to 53% more water than unprocessed soy hulls. These results can be used to predict the functional properties of soy hulls when exposed to different media during product formulation.     

PARTICLE SIZE EFFECT ON SOY PROTEIN ISOLATE EXTRACTION

This study was undertaken to determine if the yield and purity of soy protein isolates could be improved by changing the particle size of the starting raw material. Soy protein isolates were extracted from hexane defatted soy flour ground to three different average particle sizes (89.5 ± 1.1, 184.2 ± 1.6 and 223.4 ± 6.4 µm). By decreasing the average particle diameter of the starting raw material (soy flour) from 223.4 to 89.5 µm the total solids recovery increased from 23 to 32% (P = 0.00008), while the protein recovery increased from 40 to 52% (P = 0.00004). Final protein content (i.e., purity) of the soy protein isolates was not significantly impacted by average particle size. The results clearly demonstrated that protein recovery can be increased by >30% by decreasing the average particle size of the starting raw material (i.e., defatted soy flour), without having any detrimental impact on the purity of the final soy protein isolate.     

EFFECTS OF SOY PARTICLE SIZE AND COLOR ON THE SENSORY PROPERTIES OF GROUND BEEF PATTIES

A study was conducted to assess the effect of both size and color of textured soy protein particles on the visual and textural properties of extended (20% replacement) ground beef patties. A trained texture profile panel judged the hardness, cohesiveness, chewiness, moistness, and oiliness of nine different samples. In addition, judgments of the visual attributes of darkness, size of particles, and density of particles were made. Significant effects of soy ingredient were found for all judged attributes. It was concluded that soy ingredients having particle sizes smaller than the diameter of the openings of the grind plate used to process the meat/soy mixture produced the greatest change in the texture of the ground beef patties, because these particles passed through the grind plate unscathed, producing an easily discernable matrix of large meat particles and small soy particles. It was also concluded that carmel-colored soy ingredients produced less lightening of the cooked samples than uncolored soy ingredients.     

THE EFFECT OF HEAT AND SHEAR ON THE VISCOELASTIC PROPERTIES OF SOY FLOUR DOUGH

This paper is concerned with the effect of heat and shear on the rheological properties of defatted soy dispersions and doughs of 30 to 60% flour by weight. Capillary and rotary rheometers (Rheometrics Mechanical Spectrometer) were used to heat doughs up to 75° C and shear them simultaneously. In one series of experiments using a modified Instron capillary rheometer the doughs were heated to several different temperatures and then sheared. The linear viscoelastic properties of the dough which were determined by means of a plate-plate rheometer were then compared to the fresh dough and those of a heated but nonsheared dough. In another experiment a cone-and-plate rheometer was used to heat and shear the dough. The linear viscoelastic response of the dough was used to monitor any changes as it was heated and sheared. It was observed that only in the higher moisture dispersions (i.e., moisture contents greater than 50%) were there any signs of an increase in rheological properties which might be associated with “cooking”. It was concluded that cooking of soy flour doughs most likely does not involve the formation of a permanent network formed by covalent chemical bonds. Hence, in extrusion cooking processes involving soy flour doughs, it may not be necessary to treat the rheological properties of the dough as a thermosetting system.     

EFFECT OF UNIMODAL PARTICLE SIZE AND PULP CONTENT ON RHEOLOGICAL PROPERTIES OF TOMATO PUREE

The vane method in controlled shear stress mode was used to determine the yield stress and the shear rate—shear stress data of tomato purees containing 10–35% pulp of two different average particle sizes: 0.34 and 0.71 mm. Consistency index and apparent viscosity increased significantly with pulp content and decreased with average particle size. The effect of pulp weight fraction (P) on relative viscosity (η_r) could be described by the single parameter equation: η_r= [1 – (P/A)]⁻², while the effect of particle diameter on η_r could be described using Peclet number. Magnitudes of yield stress determined directly by the vane method were higher than those obtained by using the Casson model, and were proportional to the square of pulp content. Reduced Casson yield stress—P data on purees of both particle sizes followd a single curve. Effects of pulp content and particle size on vane yield stress and apparent viscosity were evident from the correlation forms with high values of R².     

EFFECT OF PARTICLE SIZE ON THE WATER SORPTION PROPERTIES OF CEREAL FIBERS1

Six particle size fractions were prepared by grinding and sieving stabilized hard red wheat bran, oat fiber, and corn bran. Water adsorption indices (WAI's) and effective diffusion coefficients (D_eff) were measured for all size fractions. WAI's of wheat bran decreased with particle size. WAI's of oat bran increased as particle size decreased and the WAI's of corn bran fractions did not vary as much as the other fibers. The D_eff's of wheat increased, of oat decreased, and of corn were about the same as the particle size decreased. The wheat D_eff was less than that of corn which was less than that of oats. Monolayer moisture content and bulk moisture content at high A_w were determined from moisture sorption isotherms measured on the smallest particles. There was no difference in the monolayer moistures but both corn and wheat brans adsorbed much more water at high A_w than did the oat bran. Effect of particle size on water sorption and, by inference, some types of functionality cannot be generalized and must be determined for each type of fiber.     

全脂大豆蛋白对面条品质影响的探讨

通过在面粉中添加不同比例的全脂大豆蛋白，探讨了其对蛋白质品质、面团流变学特性、面条色泽、断条率、咀嚼感、爽口感及面条蒸煮品质和感官品质的影响。结果表明，在面粉中加入8％的全脂大豆蛋白可显著提高面粉的蛋白含量和湿面筋含量，改善了面团的流变学特性及面条的韧性和口感，既增加了面条营养价值，又提高了面条的质量和加工性能。     

EFFECT OF THE AMOUNT AND PARTICLE SIZE OF WHEAT FIBER ON TEXTURAL AND RHEOLOGICAL PROPERTIES OF RAW,DRIED AND COOKED NOODLES

ABSTRACT

Textural and rheological properties of raw, dried and cooked noodles enriched with wheat fibers were simultaneously evaluated by a texture analyzer. Increasing wheat fiber level led to an increase in the cutting force of raw and cooked noodles and a decrease in the breaking force of dried noodle as well as extensibility of raw and cooked noodles. Generally, raw, dried and cooked fiber‐enriched noodles with small fiber size had higher breaking force and extensibility and lower cutting force than that with large fiber size. The textural properties of raw noodle are good indicators to predict the strength and elasticity of dried and cooked noodles. Both three‐term Maxwell and Peleg–Normand models were found to fit well to the stress relaxation data of cooked fiber‐enriched noodle. Significant correlations were found between empirical textural properties and fundamental mechanical stress relaxation parameters.

PRACTICAL APPLICATIONS

Texture is one of the important factors affecting the quality of noodles. The increased consumption of noodles enriched with wheat bran or purified wheat fiber is proposed for health reasons. The textural properties of fiber‐enriched noodles are affected by the type, amount and size of wheat fiber. The cutting force, tensile strength and extensibility of raw noodle are good indicators to predict the strength and elasticity of dried and cooked noodles. Results of this study suggest that raw, dried and cooked fiber‐enriched noodles with good quality can be prepared by adding 4–8% fine wheat bran or 4% fine purified wheat fiber.     

EFFECT OF PARTICLE SIZE ON VISCOAMYLOGRAPHIC BEHAVIOUR OF RICE FLOUR AND VERMICELLI QUALITY

The effect of particle size on the cooking behaviour of rice (Oryzae sativa, sub sp. Indica kato) flour was studied with the Brabender Viscoamylograph. Among the flours of different average particle sizes (307, 214, 165, 138, 114, 90 and 71 μ) studied, flours of 138 and 165 μ showed high breakdown ratios of 0.984 and 0.866 and set back ratios of 2.333 and 2.143, respectively. Comparatively, for vermicelli making, the flours of 138 and 165 μ yielded a product with better scores for textural profile, highlighting the importance of particle size of flours in the preparation of rice based vermicelli.     

EFFECT OF PARTICLE SIZE ON THE QUALITY OF PEANUT PASTES

A spread made from light colored, bland peanut paste flavored with cheese, meat, fruit or chocolate would enhance the probability of increased utilization of peanuts. The effect of particle size on quality of pastes prepared from whole peanut kernels subjected to water extraction (WE) and chopping was determined. Results indicated that the paste prepared from coarsely or moderately chopped peanuts was found to be light in color and have the lowest flavor intensity scores. Paste prepared from finely chopped peanuts had the darkest color among all treatments.     

RHEOLOGICAL PROPERTIES OF NONCOHESIVE APPLE DISPERSION WITH HELICAL AND VANE IMPELLERS: EFFECT OF CONCENTRATION AND PARTICLE SIZE

The proportionality constant, k_s, between shear rate, γ, and agitation velocity, N, for a helical ribbon‐screw (HRS) agitator was 17.8. Using the HRS agitator, values of consistency index K and the flow behavior index n of 14 apple pulp suspensions at seven different solids concentrations and two average particle diameters 0.71 mm and 1.21 mm were determined; in addition, values of the Casson viscosity η_c and yield stress σ_OC were also calculated. The magnitudes of K increased and of n decreased with increase in pulp concentration. Experimental values of the vane yield stress, σ_Oν, measured with a six‐blade vane increased with increase in pulp content. The values of σ_OC obtained using the Casson model were close to the experimental values σ_Oν. The effect of particle size on the relative viscosity, η_r, was correlated with Peclet number.     

EFFECT OF PARTICLE SIZE AND SAMPLE SIZE ON LIPID STABILITY OF MILLED FLAXSEED (Linum usitatissimum L.)

Experiments were conducted to determine the effect of sample size and particle size on lipid oxidation of milled flaxseed. An initial experiment showed that most of the lipid oxidation detected in milled flaxseed samples occurred on the surface that was exposed to the air during storage. In a subsequent experiment, milled flaxseed at 100, 200 and 300 g were stored in the dark in rectangular pans for 8, 24 and 48 days at 50C. Lipid oxidation, as determined by surface lipid content, peroxide value and α-linolenic acid content, was lower in the 300 g samples than in the 100 g samples of milled flaxseed. Large versus small samples had less apparent lipid oxidation because of their inherently lower surface to volume ratio. In a third experiment, oxidation was lower in lipid extracted from coarse ( > 600 µm) than fine particles ( < 600 µm), after 48 days of storage.

PRACTICAL APPLICATIONS

This research has practical applications to the flaxseed milling and food industries. These results show that assessment of lipid oxidation in milled flaxseed needs to consider sample size (collection). Milled flaxseed oxidized predominantly at the sample surface where a polymerized layer of flaxseed particles formed over time. Relatively little oxidation occurred in the interior of the sample. Thus, sampling from the surface or interior of a milled flaxseed sample will end in different results and conclusions. Similarly, results will vary with surface : interior ratio of milled flaxseed. Food manufacturers may want to discard the top layer of milled flaxseed that has been exposed to air. Lipid oxidation was less with coarse than fine particles. Thus it would be prudent not to use milled flaxseed with a finer particle size than is necessary for acceptable end-use quality.     

RATIONALE FOR PARTICLE SIZE EFFECT ON RATES OF ENZYMATIC SACCHARIFICATION OF MICROCRYSTALLINE CELLULOSE

Commercially available microcrystalline cellulose (MCC) preparations are widely used as substrates for the characterization of cellulolytic enzymes. The intent of this paper is to demonstrate the importance of considering particle size when using these substrates and to provide a rationale for particle-size related phenomena. Rates of saccharification of MCC substrates having average particle sizes of 20, 50 and 100 μm were compared under typical Trichoderma reesei cellulase-based saccharification conditions. The results demonstrate that MCC substrates of different particle size are not equivalent with respect to their kinetics of enzymatic saccharification. The three MCC substrates were shown to be essentially equivalent with respect to physical and chemical parameters commonly correlated with rates of saccharification. Hence, the influence of particle size on rates of MCC saccharification is likely due to the relative importance of mass transfer limitations within the agglomerate particles that make up these substrates.     

EXTRUDED CORN MEAL AND WHEY PROTEIN CONCENTRATE: EFFECT OF PARTICLE SIZE

Blends of whey protein concentrate (WPC) and corn meal, which were separated into four particle fractions (residual on a #30 screen, #40 screen, #60 screen and through a #60 screen), were extruded at two moisture conditions (23 and 28%) to determine the effects of particle size on the extrudate properties. Smaller particle size fractions exhibited increased solubility and significantly higher viscosity both with and without added protein. When WPC was added to the corn meal, a large reduction in paste viscosity was observed regardless of the particle size. The blend with similar particle size distributions of corn meal and WPC had a significantly higher viscosity than the other blends. The expansion ratio, porosity and breaking strength of this blend, when extruded at the lower moisture content, were improved to the extent that they behaved similarly to extrudate made from corn meal alone.