A method of retarding lipid digestion of a chocolate protein bar

Abstract

This invention provides a method for delaying lipid digestion in chocolate protein bars. The method involves thermally inducing the granulation of a whey protein dispersion at pH 5.0–6.0 to prepare porous particles with a porosity >76%. Subsequently, vegetable oil is directly loaded onto these particles to construct an oleogel with an oil-holding capacity >99%, which replaces the MLCT oil in the protein bars. Results show that this oleogel imparts better elastic recovery to the protein bars (nearly doubling the resilience). The three-dimensional network of protein particles significantly hinders the physical encapsulation of lipids, reducing the bioavailability fraction of free fatty acids from 61.26% to 40.06% at 240 min, thus effectively delaying lipid digestion. This invention provides excellent oral sensory properties and sustained energy release characteristics while reducing saturated fat.

Description

Technical Field

[0001] This invention relates to the field of food processing and functional food technology, specifically to a method for delaying lipid digestion in chocolate protein bars. Background Technology

[0002] Chocolate protein bars are a type of functional food characterized by their high protein content. Their convenience and nutritional fortification make them popular among athletes and fitness enthusiasts, as well as consumers focused on weight management. To maintain the textural properties of the protein bars and ensure processing performance, existing products commonly add medium- and long-chain fatty acid oils (MLCTs) as a fat component. However, MLCTs can contain over 90% saturated fatty acids, resulting in excessively high saturated fatty acid intake from protein bar products. Long-term consumption of these products is closely associated with an increased risk of cardiovascular disease.

[0003] Furthermore, the lipid digestion behavior of chocolate protein bars is also noteworthy. Lipid components present in the protein bar itself, in the form of liquid oils or traditional solid fats, undergo rapid hydrolysis in the gastrointestinal tract, resulting in a large postprandial lipid response. This is detrimental to the stable regulation of lipid metabolism, especially for consumers who need to control their energy intake and blood lipid levels over the long term. Therefore, how to reduce the saturated fatty acid content in protein bars while regulating their lipid digestion rate has become one of the urgent technical problems to be solved in this field.

[0004] To address the aforementioned issues, the main solutions currently available are as follows: First, improving the fatty acid composition of protein bars by directly adjusting the oil composition. For example, partially replacing MLCT with vegetable oils high in unsaturated fatty acids to reduce the overall saturated fatty acid level of the product. However, this approach faces the following problems: liquid vegetable oils are highly fluid at room temperature, making it difficult to provide the necessary textural support in the protein bar system, easily leading to oil seepage, softening, and other quality deterioration phenomena, affecting the product's processing adaptability and consumer acceptance. Second, structurally modifying liquid oils by adding exogenous structural agents to achieve physical properties similar to solid fats, thereby balancing fatty acid composition optimization and textural maintenance. Among these, oleogel technology is a rapidly developing strategy for constructing structured oils in recent years. Oleogels are semi-solid materials that immobilize liquid vegetable oils within a three-dimensional network of gelling agents, endowing liquid oils with rheological properties similar to solid fats. Based on this, oleogels using proteins as gelling agents have attracted widespread attention due to their combination of structural functions and nutritional properties. Existing research has reported a variety of strategies for preparing protein oleogels, mainly including emulsion template method and direct method. Protein oleogels prepared by the above methods have achieved partial or complete replacement of traditional fats in systems such as spreads, dairy products and baked goods.

[0005] However, the aforementioned oleogel technology still has the following shortcomings when applied to chocolate protein bar systems. First, the lipids in the protein bar are not present in a continuous lipid phase, but rather as a dispersed phase filling a dense protein-carbohydrate solid matrix. Their rheological behavior, oil-holding capacity, and impact on the structural integrity of the protein matrix are fundamentally different from those of lipids in a continuous lipid phase. Existing oleogel technologies are mostly applied to continuous lipid phase environments, and their optimized parameters are difficult to directly apply to protein bars, a system where the solid phase is continuous. Second, current research on oleogel alternatives focuses on reducing saturated fat content and improving textural properties, without addressing the regulation of lipid digestion behavior or incorporating changes in lipid hydrolysis kinetics after substitution into evaluation indicators and optimization goals. Third, existing studies, when optimizing protein oleogel preparation parameters, all use the textural simulation effect of the target system as the evaluation standard, lacking a parameter screening strategy guided by digestive behavior regulation. Therefore, while the resulting oleogel improves fatty acid composition, it is difficult to achieve active regulation of lipid digestion rates.

[0006] In summary, regarding the high saturated fatty acid content and rapid lipid digestion issues caused by MLCT in chocolate protein bars, current technologies lack a fat substitution solution that can simultaneously reduce saturated fatty acid content and regulate lipid digestion behavior. Developing a fat substitution technology suitable for protein bar systems that can actively regulate the lipid hydrolysis rate while maintaining product texture has become a pressing technical problem to be solved in this field. Summary of the Invention

[0007] To address the aforementioned technical problems, the purpose of this invention is to provide a method for delaying lipid digestion in chocolate protein bars. This method involves preparing whey protein particle oil gel under specific process conditions to replace medium- and long-chain fatty acid edible oils in the preparation of chocolate protein bars. This achieves the goal of reducing saturated fat content, improving the texture of chocolate protein bars, and significantly delaying lipid digestion.

[0008] To achieve the above objectives, the present invention first provides a method for delaying lipid digestion in chocolate protein bars. The method involves replacing the medium- and long-chain fatty acid edible oils in the protein bar body with whey protein particle oil gel and preparing chocolate protein bars. The whey protein particle oil gel contains whey protein particles and vegetable oil, and does not contain an aqueous phase. The whey protein particles are obtained by heating a whey protein dispersion in a water bath at a pH of 5.0 to 6.0, followed by ice bath cooling, homogenization, centrifugation, washing, and freeze-drying.

[0009] In one embodiment of the present invention, the proportion of medium- and long-chain fatty acid edible oil replaced by whey protein particle oleogel is 80-100%, preferably 100%.

[0010] In one embodiment of the present invention, the vegetable oil is sunflower seed oil, and the oil content in the oil gel is 30-60%, preferably 60%.

[0011] In one embodiment of the present invention, the whey protein dispersion has a mass fraction of 4-20%, preferably 15-20%, and the water bath heating temperature is 85-90°C, with a heating time of 15-20 min.

[0012] In one embodiment of the present invention, the homogenization is performed by mixing whey protein gel formed after cooling in an ice bath with water and then performing high-speed shearing. The mass ratio of whey protein gel to water is 1:2 to 2:1, the recommended high-speed shearing speed is 10,000 to 18,000 rpm, and the shearing time is 2 to 5 minutes.

[0013] In one embodiment of the present invention, centrifugation is performed at 4000g for 20 min, and freeze drying is performed by dispersing the precipitate in water to form a dispersion with a concentration of 5%~10% (w / w), followed by freeze drying at a freezing temperature of -40~-80℃ and a vacuum degree of <20 Pa for 48 h.

[0014] In one embodiment of the present invention, the whey protein particle oleogel is prepared by adding vegetable oil dropwise to whey protein particles and then stirring thoroughly.

[0015] The present invention also provides the use of the above-mentioned whey protein particle oil gel in improving the lipid digestibility of chocolate protein bars, the use including replacing the medium and long chain fatty acid edible oils in chocolate protein bars with the above-mentioned whey protein particle oil gel.

[0016] The present invention also provides a low-fat digestibility chocolate protein bar, the chocolate protein bar comprising a protein bar body and a chocolate sauce coated on the surface of the protein bar body, wherein, by mass percentage, the components of the protein bar body include 15% to 30% whey protein particle oil gel, 10% to 25% whey protein powder, 25% to 40% glucose syrup, 10% to 20% oat bran, and 5% to 15% maltodextrin.

[0017] The present invention also provides a method for preparing the above-mentioned low-lipid digestibility chocolate protein bar, comprising the following steps: thoroughly mixing whey protein powder, oat bran, maltodextrin and whey protein granule oleogel, then adding glucose syrup and continuously stirring at 60 °C until uniform, pouring into a mold and curing at 4 °C for 1 h, baking at 160 °C for 20 min, removing and cooling to obtain the protein bar body, and coating the surface of the protein bar body with chocolate sauce to obtain the chocolate protein bar.

[0018] Beneficial effects: 1. This invention uses whey protein particles and sunflower seed oil oleogloss as fat substitutes to replace medium- and long-chain fatty acid edible oils in the preparation of protein bars. The prepared protein bars contain a higher content of unsaturated fatty acids, reducing the saturated fatty acid content of the protein bar itself by about 80%, which is more in line with the recommendations of healthy dietary guidelines. At the same time, the prepared protein bars not only have better textural properties, namely lower hardness, chewiness, and high resilience, but also are easier to form into boluses and are more suitable for swallowing, significantly improving the oral processing characteristics of the product; more importantly, the protein bars prepared by the method of this invention can significantly delay lipid digestion.

[0019] 2. The present invention further adjusts the whey protein concentration to 15-20%, which can prepare an oleogel based on whey protein hydrogel particles. The oleogel has a denser network structure, which can achieve better encapsulation of lipids and significantly delay lipid digestion. The lipid digestion delay of the prepared protein bar is as high as 34.6%.

[0020] 3. The method of this invention is clean and simple, suitable for industrial production. The drying template method only requires two raw materials: food-grade whey protein and sunflower seed oil. It does not require organic solvents or high-energy-consuming special equipment. The preparation process is simple and facilitates standardized and large-scale production. Attached Figure Description

[0021] Figure 1 Confocal laser scanning microscopy (CLSM) images of the oleogels of Examples 1-3 and Comparative Example 1; Figure 2 Strain scan (A) and frequency scan (B) rheological properties of whey protein particle oleogels in Examples 1-3 and Comparative Example 1; Figure 3 This is a confocal micrograph of the chyme during the in vitro gastrointestinal digestion of the protein bar in Example 1. Detailed Implementation

[0022] The following examples are used to illustrate the present invention, but are not intended to limit the scope of protection of the present invention. Those skilled in the art can make appropriate adjustments to the source of raw materials, proportions, and process parameters without departing from the spirit and essence of the present invention.

[0023] This invention uses whey protein isolate (WPI, purchased from Aria Foods, Denmark) as the raw protein. Commercial food-grade raw materials include sunflower seed oil, cocoa butter (Laibang Company, Jinjiang, China), skim milk powder (Yili Group, Hohhot, China), cocoa powder (Gaolegao Foods Company, Tianjin, China), sucrose, lecithin, glucose syrup, oat bran, maltodextrin, and medium- and long-chain fatty acid edible oil (MLCT). All analytical-grade chemical reagents were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China).

[0024] Test method: Bulk density: After weighing whey protein particles or WPI, transfer them to a graduated cylinder. Bulk density (ρ) b The calculation is based on mass (m) and bulk volume (V). b The ratio of ).

[0025] Porosity: Calculate porosity (%) using the following formula.

[0026] Where ρ b ρ is the bulk density (g / cm³). t The true density of whey protein is 1.35 g / cm³.

[0027] Surface hydrophobicity: Determined using the 8-aniline-1-naphthalenesulfonic acid (ANS) fluorescent probe method. 0.5 mg / mL protein sample was mixed with 20 µL of 8.0 mmol / L ANS solution, vortexed, and incubated in the dark for 15 min. Fluorescence intensity was measured at room temperature using a Hitachi F-4700 fluorescence spectrophotometer with excitation wavelength of 390 nm, emission wavelength of 470 nm, and a slit width of 5 nm. Surface hydrophobicity (% mg) -1 The initial slope is represented by the graph of fluorescence intensity versus protein concentration.

[0028] Particle size determination: Protein particles and WPI were hydrated in distilled water of their respective pH values ​​at 1 mg / mL for 2 h (with continuous stirring). The particle size distribution was determined using a Mastersizer 3000 laser particle size analyzer (Malvern, UK) at 25°C with a refractive index of 1.46 and a Hydro EV wet dispersion unit.

[0029] Oil holding capacity: Take 1.0 g of oleogel sample and place it into a pre-weighed microcentrifuge tube. Centrifuge at 10000 g for 15 min (25°C). Gently pour out the separated oil and weigh again. The oil holding capacity is expressed as the percentage of oil retained in the sample by mass.

[0030] Microstructure observation (CLSM): Microstructure characterization was performed using a Nikon Eclipse Ti2 inverted laser confocal microscope (CLSM). The protein phase was fluorescently labeled with Nile Blue (1 mg / mL ethanol solution), and the excitation source was a 633 nm He-Ne laser.

[0031] Small Amplitude Oscillation Shear (SAOS): An MCR 302e rheometer (Anton Paar, Austria) with 25 mm parallel plate clamps at 1.0 mm spacing was used. Equilibrium was maintained for at least 120 s under a normal force of 0.2 N and at 25°C. First, a strain scan (0.01%–1000%, 1.0 Hz) was performed to determine the linear viscoelastic region (LVE); subsequently, a frequency scan (0.01–10 Hz) was performed within the LVE range (with a fixed strain of 0.1%). Viscoelasticity was characterized by continuous monitoring of the storage modulus (G′) and loss modulus (G″).

[0032] Large Amplitude Oscillation Shear (LAOS): Strain scanning (0.01%–1000%) was performed on the samples at 25°C and 1.0 Hz. The variations of G′ and G″ with strain amplitude were recorded, and the relationship between shear stress, strain, and strain rate was analyzed. The nonlinear response was characterized using Lissajous-Bowditch (LB) plots.

[0033] Texture analysis: The texture analyzer was used to perform full texture analysis. After chewing for 24 seconds (30 times in total) at a fixed frequency (1.25 times / s), the food bolus was collected and the TPA test was performed (compressed to 65% deformation in two cycles).

[0034] In vitro simulated gastrointestinal digestion was performed according to the modified INFOKES protocol. To ensure consistent fat content across samples, 24 g of control protein bars and 36 g of oleogel-based protein bars were ground in a food processor for 30 seconds to ensure uniform particle size before being used in the digestion experiment. 50 g of simulated saliva (SSF, pH 7.0, containing 2000 U / ml α-amylase) was added to the ground samples, and the mixture was gently stirred and digested at 37 °C for 5 min to simulate oral chewing and initial starch hydrolysis. After oral digestion, 75 g of simulated gastric juice (SGF, pH 2.0, containing 2000 U / ml pepsin and 60 U / ml gastric lipase) was added to adjust the pH to 2.0, and the mixture was gently stirred and digested in a 37 °C water bath for 2 h. At each gastric digestion stage (0, 30, 60, and 90 min), 1.5 mL samples were taken and immediately placed on ice to terminate the reaction. An equal volume of fresh SGF was added after each sampling to maintain a constant digestion volume. After gastric digestion, 150 g of simulated intestinal fluid (SIF, pH 7.0, containing 100 U / ml pancreatic enzyme activity, 10 mM bile salts, and 0.6 mM CaCl2) was added to adjust the pH to 7.0. The system was then incubated in a 37 ℃ water bath with gentle stirring for 2 h. At each of the intestinal digestion stages (0, 30, 60, 90, and 120 min, corresponding to total digestion times of 120, 150, 180, 210, and 240 min), 1.5 ml samples were taken and processed in the same manner. All samples were... Store at 40℃ for later use.

[0035] At each time point, the digested samples were centrifuged at 10000 × g for 10 min at 4 ℃, and the supernatant was used for determination. A commercial non-esterified free fatty acid (NEFA) assay kit was used, following the manufacturer's instructions: 0.2 ml of supernatant was taken, and 0.5 ml of buffer, 1.0 ml of copper reagent, and 4.0 ml of chloroform were added sequentially. The mixture was vortexed for 2 min to extract thoroughly, and centrifuged at 3500 rpm for 10 min. 2.0 ml of the lower organic phase was carefully aspirated, and 0.25 ml of chromogenic reagent was added. After incubation at room temperature for 2 min, the absorbance was measured at 440 nm (with chloroform as a blank control). A standard curve was plotted using palmitic acid (PALM) standard (1000 μmol / L), and the concentration of free fatty acids in each sample was calculated.

[0036]

[0037] Where, m NEFA释放 The total mass (g) of free fatty acids measured in the digestion solution at each time point is given. The total lipids in sample m are the total lipids (g) contained in the protein bar sample participating in the digestion experiment, which were determined in advance by Soxhlet extraction.

[0038] Example 1 Preparation of whey protein particles: WPI powder was dissolved in deionized water at a concentration of 20% (w / w) and stirred continuously at room temperature for 24 h to ensure complete hydration. The pH of the WPI solution was adjusted to 5.0 with 6 M HCl, and the solution was heated in a 90℃ water bath for 20 min to induce gelation, promoting protein denaturation and the formation of a network structure. The resulting gel was immediately cooled in an ice-water bath, and twice the volume of deionized water was added. The mixture was homogenized using a high-speed shear mixer (IKA T25, 14000 rpm, 3 min) to obtain a fine particle suspension. The suspension was centrifuged at 4000 × g for 20 min, the supernatant was discarded, and the mixture was washed three times with deionized water to remove soluble protein. The precipitate was redispersed in water and freeze-dried for 48 h to obtain whey protein particles (WPHP 5.0) powder.

[0039] Preparation of whey protein particle oleogel: Sunflower seed oil was gradually added dropwise to the above whey protein particle WPHP 5.0 powder. After each addition, the mixture was stirred thoroughly by hand. The next round of addition was only continued after the previous oil was completely adsorbed, so as to prepare an oleogel with an oil content of 60%.

[0040] Chocolate protein bars with low fat digestibility Chocolate protein bars consist of the protein bar itself and a chocolate sauce coating the surface of the protein bar. The protein bar formula is as follows: 21 g whey protein granules oil gel, 16.6 g WPI powder, 30 g glucose syrup, 16 g oat bran, and 8 g maltodextrin.

[0041] Preparation of protein bar body: First, mix the dry ingredients with the oil gel thoroughly, then add glucose syrup and stir continuously at 60 ℃ until uniform. Pour into a mold and solidify at 4 ℃ for 1 h. Bake at 160 ℃ for 20 min. After cooling, the protein bar body is obtained.

[0042] Control group protein bars: The protein bar formula is as follows: 21 g of medium- and long-chain fatty acid edible oil, 25 g of WPI powder, 30 g of glucose syrup, 16 g of oat bran, and 8 g of maltodextrin.

[0043] Example 2 The difference between Example 2 and Example 1 is that the pH during the preparation of whey protein particles is 5.7, and whey protein particles WPHP 5.7 powder is obtained.

[0044] Example 3 The difference between Example 3 and Example 1 lies in the preparation method of the whey protein particles. The specific preparation method is as follows: WPI powder was dissolved in deionized water at a concentration of 4% (w / w), stirred at room temperature for 2 h, and then stored at 4 °C overnight to ensure complete hydration. The pH was adjusted to 5.0 with 6 M HCl, and the mixture was heated in an 85 °C water bath for 15 min to promote the formation of densely packed globular protein aggregates. The sample was immediately cooled in an ice bath and then homogenized with additional water (2:1, v / v) using a high-speed shear mixer (14000 rpm, 3 min). The centrifugation and washing procedure was the same as in Example 1, and the final product was freeze-dried for 48 h to obtain WPMP 5.0 powder.

[0045] Example 4 The difference between Example 4 and Example 1 is that the oil content in the oleogel is 30%.

[0046] Example 5 The difference between Example 5 and Example 1 is that when preparing the protein bar body, whey protein particle oleogel is used to replace 80% of the medium- and long-chain fatty acid edible oil. That is, the formula of the protein bar body is: 16.8g whey protein particle oleogel, 18.3g WPI powder, 30g glucose syrup, 16g oat bran, 8g maltodextrin, and 4.2g medium- and long-chain fatty acid edible oil (MLCT oil).

[0047] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that whey protein particles were not prepared; instead, whey protein powder was directly mixed with sunflower seed oil to prepare an oil gel, and the corresponding protein bars were prepared.

[0048] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the concentration of WPI powder in deionized water was changed to 10%.

[0049] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the type of oil was changed, with palm oil replacing sunflower seed oil.

[0050] Comparative Example 4 The difference between Comparative Example 4 and Example 3 lies in the preparation method of the oleogel. Specifically, WPI powder was dissolved in deionized water at a concentration of 4% (w / w), the pH was adjusted to 5.0, and the mixture was heated at 85 °C for 15 min and then cooled in an ice bath to obtain an aqueous heat-induced protein gel. Subsequently, an equal amount of sunflower seed oil was added directly to this aqueous gel, and emulsification was performed using a high-speed shear mixer (14000 rpm, 3 min) to prepare an aqueous protein-oil system (approximately 50% water content), which was used to replace the MLCT oil in the protein bars in an equal amount.

[0051] Comparative Example 5 The difference between Comparative Example 5 and Example 3 is that the oil gel was replaced with an emulsion gel. The emulsion gel preparation included the following steps: WPI powder was dissolved in deionized water at a concentration of 4% (w / w), the pH was adjusted to 5.0, sunflower seed oil was added (oil-to-water ratio 1:1, v / v), a primary emulsion was prepared using a high-speed shear mixer (14000 rpm, 3 min), and then heated at 85 °C for 15 min to induce emulsion gelation. After cooling in an ice bath, a WPI emulsion gel (containing approximately 50% water and approximately 50% oil) was obtained. MLCT oil (21 g) with a fat content similar to that in the protein bars (approximately 42 g) was used to replace MLCT oil, and the remaining ingredients were adjusted to maintain the balance of water and protein in the total formulation.

[0052] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that the oil content in the oleogel is 70%.

[0053] The physicochemical properties of the whey protein particle samples in each example and comparative example were characterized, and the results of some examples and comparative examples are shown in Table 2. The experimental results show that the whey protein particles prepared in Example 1 have a relatively dense network structure, specifically exhibiting high packing density and low porosity, while also possessing good surface hydrophobicity. This is mainly because the whey protein particles in Example 1 were prepared at pH 5.0 (close to the isoelectric point pI 5.1 of β-lactoglobulin), resulting in more compact aggregation due to reduced electrostatic repulsion, higher surface hydrophobicity, and larger particle size. Examples 2 and 3, compared to Example 1, changed the pH and the concentration of WPI powder in deionized water during whey protein particle preparation, respectively. The results show that the whey protein particles prepared at a higher pH have a looser network structure and the worst surface hydrophobicity. Furthermore, Example 3 easily yielded whey protein microgels at a lower protein concentration, exhibiting the loosest network structure.

[0054] The experiment also investigated the effect of different WPI concentrations on the whey protein network structure. The experiment found that when the whey protein concentration was 15-20%, whey protein easily formed hydrogels under low pH and heat conditions, resulting in a denser network of whey protein particles. At lower WPI concentrations, whey protein easily formed microgels, which had a looser network structure, exhibiting greater porosity and lower packing density.

[0055] Both excessively high and low protein concentrations can affect the formation of the whey protein network structure. When the whey protein concentration is too high, such as reaching 30%, the solution rapidly forms a heterogeneous, rigid gel mass during heating, which cannot be effectively dispersed into a particulate suspension through subsequent centrifugation and washing, resulting in severe powder agglomeration after freeze-drying. When the whey protein concentration is too low, such as as low as 1%, the protein cannot form an effective network structure after heat treatment, resulting in very little precipitation after centrifugation and a freeze-drying yield of less than 5%, making it impossible to prepare effective particulate oleogels and unsuitable for protein bar production.

[0056] Table 1 Comparison of Physicochemical Properties of Whey Protein Particles

[0057] Table 2 and Figure 1 The oil-holding capacity and confocal laser scanning microscopy (CLSM) images of the oleogels of Examples 1-3 and Comparative Example 1 are presented respectively. As can be seen from Table 2, Examples 1-3 have considerable oil-holding capacity, which is significantly higher than that of the WPI-based oleogel (Comparative Example 1, 90.78%). The confocal laser scanning microscopy images confirm that the particulate oleogels of Examples 1-3 form an interconnected, dense three-dimensional network, while the WPI-based oleogel exhibits a discontinuous, isolated aggregate structure, consistent with its lower oil-holding capacity.

[0058] Table 2 Oil-holding capacity of whey protein particle oleogels

[0059] Rheological characterization results as follows Figure 2 The results show that the oleogels of Examples 1 and 3 exhibit significantly higher storage modulus G′ than loss modulus G′′ in the low strain region (γ<0.1%), displaying a gel network characteristic dominated by elasticity. Furthermore, the modulus is largely independent of frequency, indicating the formation of a strong and stable self-supporting network. In contrast, the WPI-based oleogels have significantly lower modulus, exhibit obvious frequency dependence, and a weaker network. Lissajous analysis of large amplitude oscillatory shear (LAOS) further confirms that the oleogels of Examples 1 and 3 transition from elastic to near-plastic behavior under high strain, demonstrating stronger resistance to large deformations.

[0060] Table 3 Comparison of oil-holding capacity and properties of oleogels with different oil contents

[0061] Table 3 presents the relevant properties of oleogels with different oil contents. As can be seen from Table 3, with increasing oil content, the oleogel network structure undergoes a continuous transformation from solid granular (30%) to semi-solid creamy (60%) and then to a fluid liquid (70%). Regarding oil holding capacity, both the 30% and 60% content granular oleogels maintain high oil holding capacity (>96.89%), while the 70% content group shows a decrease in oil holding capacity to 93.67%, with significant oil leakage. In terms of application effects, replacing MLCT with 60% content oleogels resulted in the lowest protein bar bolus hardness (51.73 g) and the best lipid digestion delay effect (FFA accessible fraction 40.06%, delay 34.6%). The 30% content group, due to its harder oleogels, exhibited poor mixing uniformity during protein bar preparation; the 70% content group, due to its excessive fluidity, made protein bar solidification and molding difficult. Therefore, samples with 60% oil content were selected for subsequent research. At this concentration, the oleogel exhibits a key semi-solid creamy texture, combining optimal oil retention capacity with lipid digestion regulation.

[0062] Table 4. Texture parameters of the food bolus after chewing (TPA)

[0063] Table 4 presents the textural properties of the control group protein bars and the protein bars of Examples 1, 3, and Comparative Example 1. The results show that the textural characteristics of all samples changed significantly after oral processing compared with their initial state. The control group had the highest bolus hardness (64.92 g) and chewiness, and the highest elasticity (0.608) and cohesion (0.546). The bolus hardness of Example 1 and Comparative Example 1 was the lowest (51.73 g and 50.93 g), and the highest resilience (0.081 and 0.072), indicating that the oleogel protein particle network endowed the bolus with better elastic recovery ability.

[0064] The results are shown in Table 5. During the gastric digestion stage (0-120 min), the release of free fatty acids increased in all samples; after entering the intestinal digestion stage (120-240 min), the differences between samples gradually became significant. At the end of 240 min of digestion, the control group (medium- and long-chain fatty acid edible oil (MLCT) protein bars) had the highest bioavailability fraction of free fatty acids (61.26%); the WPHP-based protein bars (40.06%) had the lowest, with a delay of approximately 34.6% compared to the control; the WPMP-based protein bars (45.68%) were second, and the WPI-based protein bars (53.14%) were in the middle. Confocal microscopy images ( Figure 3 This study confirmed that the WPHP-based protein bars had the highest amount of undigested lipids remaining at the end of digestion, corresponding to their lowest bioaccessible fraction, indicating that the dense three-dimensional network of protein particles effectively hindered the contact between lipases and lipid substrates.

[0065] Table 5. Bioaccessible fraction of free fatty acids from in vitro gastrointestinal digestion (240 min)

[0066] The experiment also investigated the effects of different oil types on the properties of oleogels. For example, in Comparative Example 3, palm oil was used instead of sunflower oil. The experiment found that palm oil is semi-solid at room temperature, making dispersion difficult during dropwise addition, and the resulting oleogel had a significantly lower oil-holding capacity than the sunflower oil-based oleogel. The protein bars prepared with palm oil showed a significantly higher saturated fatty acid content, essentially losing their lipid digestion-retarding effect. Furthermore, the advantage of reduced saturated fatty acid content in the product could not be achieved.

[0067] The results show that using sunflower seed oil as the liquid unsaturated fat phase is a necessary condition for achieving the dual objectives of reducing saturated fat and delaying digestion in this invention.

[0068] In addition, the experiment explored the properties of oleogels or fat substitutes prepared by different methods. The experiment found that Comparative Example 4, if not adequately hydrated during thermally induced gel formation, would form an aqueous oleogel system. This aqueous oleogel macroscopically exhibited a fluid emulsion-like state, failing to form a self-supporting network structure, with a G′ / G″ ratio <1 (primarily due to loss modulus), and lacking gel elasticity characteristics. The protein bars prepared with this oleogel showed significant oil seepage and stratification during the 4 ℃ curing stage, and the lipid digestion delay effect completely disappeared.

[0069] Similarly, in Comparative Example 5, the MLCT edible oil in the protein bar was replaced with an emulsion gel. Because the emulsion gel-based protein bar introduced a large amount of additional moisture, it was difficult to solidify and mold. After baking, the product showed significant shrinkage and cracking, resulting in a significant decline in sensory quality. The bolus hardness was 68.92±9.21 g, higher than the control group, while the resilience was 0.033±0.006, close to the MLCT control group. The textural improvement effect was completely lost, and the lipid digestion delay effect was also unattainable.

[0070] The results showed that the introduction of an additional aqueous phase disrupted the solid-phase continuity of the protein bar system, making it impossible to achieve texture optimization and lipid digestion regulation in the protein bar matrix.

[0071] The above results indicate that the low-fat, high-protein chocolate protein bar based on whey protein particle oleogel described in this invention can significantly reduce saturated fat content and delay lipid digestion while meeting the product's structural function and sensory quality requirements. This provides a scientific basis and feasible technical path for the industrial development of low-saturated fat functional foods.

[0072] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for delaying lipid digestion in chocolate protein bars, characterized in that, The method involves replacing the medium- and long-chain fatty acid edible oils in the protein bar body with whey protein particle oil gel to prepare chocolate protein bars. The whey protein particle oil gel contains whey protein particles and vegetable oil, and does not contain an aqueous phase. The whey protein particles are obtained by heating a whey protein dispersion in a water bath at a pH of 5.0 to 6.0, followed by ice bath cooling, homogenization, centrifugation, washing, and freeze-drying.

2. The method according to claim 1, characterized in that, The proportion of medium- and long-chain fatty acid edible oil replaced by whey protein particle oleogel is 80-100%.

3. The method according to claim 1, characterized in that, The vegetable oil is sunflower seed oil, and the oil content in the oleogel is 30-60% by mass.

4. The method according to claim 1, characterized in that, The whey protein dispersion has a mass fraction of 4-20%, and the water bath heating temperature is 85-90℃ for 15-20 minutes.

5. The method according to claim 1, characterized in that, The homogenization process involves mixing whey protein gel formed after cooling in an ice bath with water and then performing high-speed shearing. The mass ratio of the whey protein gel to water is 1:2 to 2:1, the high-speed shearing speed is 10,000 to 18,000 rpm, and the shearing time is 2 to 5 minutes.

6. The method according to claim 1, characterized in that, Centrifugation was performed at 4000g for 20 minutes. Freeze-drying involved dispersing the precipitate in water to form a dispersion with a concentration of 5%~10% (w / w), followed by freeze-drying at a freezing temperature of -40~-80℃ and a vacuum degree of <20Pa for 48 hours.

7. The method according to claim 1, characterized in that, The whey protein particle oleogel is prepared by adding vegetable oil dropwise to whey protein particles and then stirring thoroughly.

8. Use of whey protein particle oil gel in improving the lipid digestibility of chocolate protein bars, said use including replacing medium- and long-chain fatty acid edible oils in chocolate protein bars with the whey protein particle oil gel of claim 1.

9. A chocolate protein bar with a low lipid digestibility rate, characterized in that, The chocolate protein bar comprises a protein bar body and a chocolate sauce coated on the surface of the protein bar body. By weight percentage, the components of the protein bar body include 15% to 30% whey protein particle oil gel as described in claim 1, 10% to 25% whey protein powder, 25% to 40% glucose syrup, 10% to 20% oat bran, and 5% to 15% maltodextrin.

10. A method for preparing a low-lipid digestibility chocolate protein bar according to claim 9, comprising the following steps: The whey protein powder, oat bran, maltodextrin and whey protein granule oil gel are thoroughly mixed, and then glucose syrup is added and stirred continuously at 60 ℃ until uniform. The mixture is poured into a mold and cured at 4 ℃ for 1 h, then baked at 160 ℃ for 20 min. After cooling, the protein bar body is obtained. Chocolate sauce is then coated on the surface of the protein bar body to obtain chocolate protein bars.

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