Beta-carotene: Digestion, Microencapsulation, and In Vitro Bioavailability

Beta-carotene is an important nutrient for human health, but its low absorption from natural sources has led to the development of microencapsulation methods to improve stability and bioavailability. To properly design a gastrointestinal delivery system for beta-carotene, the processes occurring during digestion from mastication to absorption must first be understood. This review provides an overview of beta-carotene digestion and microencapsulation methods, with an emphasis placed on spray-drying and gelation. Given the lack of a standardized in vitro model to study the bioavailability of beta-carotene, important parameters that have been shown to affect bioavailability of beta-carotene (i.e., pH, enzyme concentration, type of model) are discussed to ensure measurements are made using physiologically relevant conditions. Current quantitative methods to measure beta-carotene after digestion are evaluated to ensure accuracy and precision of measurements. This study contributes to the knowledge concerning beta-carotene digestion, release, and absorption and provides guidelines for developing microencapsulation methods and in vitro digestion protocols to accurately measure in vitro bioavailability.     

Purine Content of Raw and Roasted Chicken Broiler Meat

Adenine, guanine and hypoxanthine were determined in raw and roasted broiler parts. The levels of adenine and guanine increased slightly when the meat was cooked. These increases were attributed to moisture and fat losses by the tissues during roasting. The level of hypoxanthine remained constant or decreased in the tissues because some of the purine was removed with the cooking juices. The cooking juices were found to contain high levels of hypoxanthine and only trace amounts of adenine and guanine.     

Processed Protein Foods Characterized by In Vitro Digestion Rates

In vitro tryptic digestion assays and determination of relative digestion rates of food proteins described previously were used to evaluate changes in the rate of digestion following processing technologies. If pH drop measurements are used, a simple mode for the determination of relative digestion rates is suggested based on the comparison with a single reference of the same protein source. The effect of processing technologies could be tested in vitro. Significant increase in the velocity of digestion was found on microwave treatment of lentil and raw soy bean as well as on acid treatment of commercial defatted soy meals. Increase in the in vitro digestion rates was reflected in decreased feed consumption per weight gain in pig feeding experiments.     

Effect of Myoinositol Phosphate Esters on In Vitro and In Vivo Digestion of Protein

Effects of phytate and its hydrolysis products (myo-inositol phophate esters) on protein digestion were investigated by in vitro and in vivo procedures. Tri-, tetra-, penta-, and hexa-phosphate ester fractions, isolated from phytate hydrolysates, inhibited pepsin digestion of casein and bovine serum albumin in vitro. The inhibition ranged from 0% for the mono- and diphosphate esters to 9–14% with the hexa-phosphate ester (phytate). The phosphate ester fractions did not significantly affect trypsin digestion of the proteins. In the in vivo study, rats were fed phytate and hydrolysates thereof (mixtures of the esters above) at levels of 1–3.5% of the diet. Under the conditions of this study, neither phytate nor its hydrolysates significantly affected protein utilization or weight gain in rats.     

Enzymatic Conditions of an In Vitro Method to Study Protein Digestion

An in vitro digestion method was proposed for studying protein digestion. Protein (casein) was submitted to peptic proteolysis in a closed system followed by hydrolysis with pancreatic enzymes in a “digestion cell” with continuous elimination of digested products by dialysis. The peptic digestion was performed with a pepsin source of high specific activity (3152 units/mg protein) with an enzyme:substrate (E:S) ratio of 1: 250. The second-step of proteolysis was carried out with pancreatin for 6 hr at an E:S ratio of 1:25. A 10 mM sodium phosphate buffer, pH 7.5, was used as the circulating dialysis buffer.     

Oxidative Stability in Raw and Roasted Pecans: Chemical, Physical and Sensory Measurements

To develop predictive relationships for sensory responses of crunchiness and rancid aroma and flavor, raw and roasted pecans were stored under two different relative humidities (55 and 65%) up to 8 mo. In response to relative humidity, rancid scores did not differ with either raw or roasted pecans. Rancid scores in raw and roasted pecans during storage most closely paralleled peroxide value and thiobarbituric acid reactive substances, respectively. Multiple regression models employing two or three oxidative and chemical measurements led to better prediction of sensory scores. In general, primary oxidative products of triacylglycerols factored into the models for raw pecans while secondary oxidative products of total lipids factored into the models for roasted pecans.     

Antioxidant Properties and Rutin Content of High Pressure-Treated Raw and Roasted Buckwheat Groats

The effect of high hydrostatic pressure treatment (200 MPa for 2, 4, and 9 min) on the total antioxidant capacity (TAC), reducing capacity (TRC), and rutin content of raw and roasted buckwheat groats was studied by an updated analytical strategy. TAC and TRC were calculated as the overall capacity of hydrophilic and lipophilic antioxidants. Antioxidant capacity was measured against the 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate) radical cation (ABTS^?+) and the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH^?), and by the photo-induced chemiluminescence assay against the superoxide anion radical (O ₂ ^?? ), whereas the reducing capacity was evaluated with the Folin-Ciocalteu reagent (FCR) and directly by the cyclic voltammetry method. Rutin content was determined by HPLC analysis. The TAC of pressure-treated raw and roasted groats was 16–20% and 12.5–17% lower in comparison with untreated groats, respectively. Hydrophilic antioxidants were the main contributor to the TAC of pressure-treated raw and roasted groats. High pressure treatment of raw groats lowered the FCR reducing capacity of hydrophilic antioxidants by an average of 12.6% and 12%, respectively. In contrast, the pressurization of roasted groats increased radical scavenging capacity by 18% on average due to the presence of hydrophilic compounds in roasted groats. The variations in the antioxidant properties of pressure-treated raw groats were accompanied by an average 47% drop in rutin content, whereas irregular changes were noted in HP-treated and roasted material.     

Raw Starch Digestion by Bacillus polymyxa beta-Amylase

Unlike plant ß-amylases, Bacillus polymyxa ß-amylase digests raw starch at a significant rate. The action of this bacterial ß-amylase on raw starch is stimulated greatly by the presence of the debranching enzyme pullulanase.     

Fiber Constituents and Fibrous Food Residue Effects on the In Vitro Enzymatic Digestion of Protein

In vitro digestibility of casein was significantly (P < 0.05) reduced as the fiber weight-to-protein weight ratio increased from 0.0:1.0 to 1.0:1.0 for isolated fiber constituents and fibrous food residues. For casein digestibility in the presence of fiber constituents, the reduction ranked in the following order: karaya gum > xylan > pectin > lignin > holocellulose. The order of reduction by fibrous food residues ranked as follows: kernel corn > blackeye pea > broccoli > brown rice > wheat bran. Gel filtration profiles of casein hydrolysates were generally not affected by the fiber constituents whereas significant alterations to greater molecular weight peptides occurred in the presence of food residues. The data supported the interaction of dietary fiber components by interference of the enzyme-substrate complex formation in proteolytic digestion.     

乳清蛋白的体外模拟消化过程及热处理的影响

探讨了乳清蛋白体外胃蛋白酶和胰蛋白酶的消化过程,以及热处理对该消化过程的影响。SDS-PAGE分析结果表明,胃蛋白酶和胰蛋白酶对乳清蛋白的体外消化作用的影响不明显。干热处理(75℃和100℃,1h)几乎不影响乳清蛋白的体外胰蛋白酶消化过程,而在同样条件下,湿热处理能显著提高胰蛋白酶对乳清蛋白的消化作用。乳清蛋白分别经75℃和100℃湿热处理30min后,再由胰蛋白酶消化8h,其氮释放率分别达到82.1%和91.3%,而未湿热处理的氮释放率仅为66.7%,表明不同热处理方式对乳清蛋白的体外消化过程产生不同的影响。湿热处理能有效地提高乳清蛋白的消化速率,且湿热处理温度越高,乳清蛋白的体外消化速率越快。     

A Method for the Rapid Analysis of Headspace Volatiles of Raw and Roasted Peanuts

A rapid headspace analysis method for evaluating the flavor quality of peanuts using gas chromatography has been developed and tested. Samples are ground, heated in glass vials for 30 min at 150°C, and the headspace injected using a gas tight syringe. After initial startup, one can screen samples for flavor defects at the rate of four per hour. Of the peaks produced from peanut headspace analysis, most have been identified by gas chromatography/mass spectrometry and eight have been related to specific flavor characteristics.     

In Vitro Inoculum Enriched with Particle-Associated Microorganisms for Determining Rates of Fiber Digestion and Protein Degradation

In trial 1, rates of neutral detergent fiber digestion were measured on alfalfa hay with conventional inoculum prepared with strained ruminal fluid or inoculum also enriched with particle-associated microorganisms. Microorganisms from particles were obtained by washing the particle residue four times with nutrient-buffer. During the first 24 h, rates of neutral detergent fiber digestion from the enriched inoculum were approximately doubled. However, by 48 h differences in extent of neutral detergent fiber digestion were small. With the enriched inoculum but not the conventional inoculum, there was a linear increase of rate of neutral detergent fiber digestion with graded application of a mixture containing potassium carbonate, which enhanced field drying of hay. In trial 2, two additional inocula were prepared from whole contents of rumen that were either blended or had been chilled at 4°C. Digestion of neutral detergent fiber was not increased by chilling, and blending tended to lower digestion. In trial 3, seven inocula were evaluated in a protein degradation study. Three inocula enriched with particle-associated organisms yielded degradation rates of casein that were more than twice those with the conventional inoculum (.17/h versus .39/h). Inocula prepared from blended whole contents of rumen (with or without chilling) or from addition of Tween 80 before chilling did not increase rates of protein degradation. Inoculum enriched with particle-associated organisms can be used routinely to obtain improved estimates of in vitro rates of fiber digestion and protein degradation.     

Effect of Maturation on Composition and In Vitro Dry Matter Digestibility of Corn Plant Parts

Corn (Zea mays L.) plants from four plots were harvested at 2-wk intervals from September 9, 1975, to December 9, 1975; separated into grain, cob, husk, leaf, and stalk; and analyzed for dry matter, crude protein, cell wall, and in vitro digestibility of dry matter. Green weight yields of all plant parts except grain decreased with advancing maturity during sampling. Percentage of dry matter increased for all parts while total dry matter per hectare increased until plant dry matter reached 35% and then decreased. Grain as a percentage of the total dry matter of plant increased to 50, then remained relatively constant. Cob, husk, leaf, and stalk made up smaller percentages of the plant dry matter as it matured. Crude protein content of leaves declined but remained fairly constant in other plant parts through this sampling period. The percentage of cell wall increased and in vitro digestibility of dry matter decreased in all plant parts except grain which remained fairly constant with maturation.Increases in grain content offset decreases in digestibilities of other plant parts until the grain was physiologically mature; then total plant digestibility decreased. Livestock producers who plan to feed stover should harvest the stover simultaneously or as soon after grain harvest as practical.     

Single-Screw Extrusion of Defatted Soy Flour, Corn Starch and Raw Beef Blends

Effects of feed moisture, fat and corn starch levels and process temperature on physical properties of extrudates of defatted soy flour-amylose corn starch-raw beef blends were investigated using response surface methodology. Contour plots showed a convex curve of expansion ratio (ER) with moisture, concave curves of bulk density (BD) and shear-force (SF) with moisture, and concave cmves of SF with each of the four extrusion variables. Fat decreased ER and increased BD, whereas corn starch increased ER. Products with high ER and low BD and SF tended to have prominent air cells, continuous protein matrices, and smooth cell wall surfaces in scanning electron micrographs. The optimum extrusion conditions for minimal SF values, with 20% non-dehydrated beef muscle and varied amounts of defatted soy flour, were: 29.1% feed moisture; 2.96% feed fat; 22% feed corn starch; and 162°C process temperature.     

Effects of Meat and Selected Food Components on the Valence of Nonheme Iron during In Vitro Digestion

Our objective was to determine whether meat and other dietary factors have the capacity to reduce nonheme ferric iron to the ferrous form during digestion. Beef, selected organic acids, selected purified proteins, red blood cells, whole blood, or blood plasma was mixed with FeCl₃ and subjected to simulated gastrointestinal digestion. Ferrozine was used to monitor the formation of dialyzable Fe(II). Ascorbic acid, glutathione and cysteine produced large increases in Fe(II) while meat (raw and cooked), hemoglobin and red blood cells yielded smaller increases. Casein, plasma, bovine serum albumin and egg albumin did not affect Fe(II) formation. Our Results suggest dietary factors which enhance iron absorption in vivo promote Fe(III) reduction in the intestinal lumen.     

Effect of Shredding Alfalfa Stems on Fiber Digestion Determined by In Vitro Procedures and Scanning Electron Microscopy

Alfalfa stems were shredded using a rotary macerator, were ammoniated, or were left untreated (control). Shredding increased extent of NDF digestion over ammoniation and control at all times from 12 to 72 h of in vitro incubation. Shredding also increased rate of disappearance of potentially digestible NDF (.032 h⁻¹ for control, .045 h⁻¹ for ammoniated, and .089 h⁻¹ for shredded). Ammoniation increased extent of NDF digestion after 36 h. Computed time required for 95% digestion of potentially digestible NDF was 94 h for control, 66 h for ammoniated and 34 h for shredded stems. Scanning electron microscopy revealed that the most prominent effect of shredding was separation of lignified and unlignified cells. Shredding split stems into a number of fragments and damaged the external cuticular waxy layer and structural integrity. Ammoniation caused cracks in lignified vascular tissue. During in vitro incubations, shredded and ammoniated cell walls were heavily colonized by bacteria by 6 h. After 24 and 48 h, large masses of bacteria were still attached to the surface of pith and lignified vascular cell walls of shredded and ammoniated stems but not control stems. Lignified vascular tissue of control stems was not degraded and structural integrity was maintained.     

模拟消化过程中酪蛋白磷酸肽持钙能力的研究

本文研究了在模拟消化过程中酪蛋白磷酸肽(Caseinophosphopeptides,CPP)抑制磷酸钙沉淀产生(即持钙能力)的作用,并在相同处理条件下对含CPP钙片A与不含CPP钙片B的持钙能力进行比较.结果表明,在弱碱性溶液中含CPP的钙片A能有效地延缓磷酸钙沉淀的产生.而不含CPP的钙片B则无此作用,但当钙片B被加入一定量的CPP后,同样能缓磷酸钙沉淀的产生.     

In Vitro Angiotensin I-Converting Enzyme Inhibition of Casein Hydrolysate Responsible for Plastein Reaction in Ethanol-Water Medium,Solvent Fractionation,and Protease Digestion

A casein hydrolysate generated by Alcalase had in vitro ACE-inhibitory activity of 44.4%, and was treated by Alcalase-catalyzed plastein reaction in ethanol-water medium. Alcalase addition, ethanol, substrate concentration, and reaction temperature optimized from experimental design were 8.36 kU/g peptides, 56.8 (v/v), 56.8% (w/v), and 37.5°C, respectively, when reaction time was fixed at 6 h. Two treated casein hydrolysates, namely TCH4 and TCH8, were obtained with reaction time of 4 and 8 h, and exhibited the highest ACE-inhibitory activity of 62.5% or the greatest reaction extent but an activity of 35.6%, respectively. Fractionation of TCH4 and TCH8 by applying ethanol-water of 7:3 (v/v) conferred the obtained supernatant (precipitate) fractionates higher (lower) activity than the parent substrate, while applying ethanol-water of 3:7 (v/v) or water led to an opposite result in activity for the fractionates. In vitro digestion of TCH4, TCH8, and their fractionates revealed that they had resistance in activity towards the investigated four proteases, as the resulted 47 out of 48 digests had higher activities than casein hydrolysate. TCH8 exhibited better protease resistance than TCH4. It is concluded that the applied plastein reaction can enhance ACE inhibition and protease resistance of casein hydrolysate.