天然鸡肉香精的制备与评价

根据Maillard反应原理 ,通过正交实验对天然鸡肉味香精的制备进行了研究 ,遵循以下反应条件可以得到较满意的结果 :m(氨基酸 )∶m(葡萄糖 ) =4∶1 ,m(甘氨酸 )∶m(丙氨酸 ) =1∶2 ,热反应温度 1 30℃ ,热反应时间 40min ,含水量w(H2 O) =40 % ,鸡肉蛋白使用Flavorzyme酶水解。并且对评价方法作了简单介绍。     

Antioxidants from a heated histidine-glucose model system. Investigation of the copper(II) binding ability

The metal binding ability of Maillard reaction products (MRP) was investigated by spectrophotometric monitoring for complex/chelate formation. In addition, the antioxidant activity of MRP, in the presence of Cu(II), was evaluated on a lipid model system consisting of sunflower seed oil/water (1∶2). Results from the Rancimat test indicated a significant decrease in pro-oxidant ability of Cu(II) in the presence of MRP in contrast to histidine alone, whether heated or not. Results from the diphenylpicrylhydrazyl method showed that, in contrast to histidine (heated or not), the antiradical ability of MRP is reduced in the presence of Cu(II), but depends on the reaction time between MRP and Cu(II).     

Die antioxidative Wirkung von Produkten der Maillard-Reaktion in Modellsystemen und gerösteten Haselnüssen

The Antioxidative Effect of Maillard Reaction Products in Model Systems and Roasted Hazelnuts Solutions of glucose and various amino acids were heated in phosphate buffer pH 7.0. Browning and reducing power of these Maillard reaction solutions showed correlation and increase in the ordeaicid -neutral — basic amino acids. Upon addition to emulsions of methyl imoleate (ML) in water the antioxidative effect increased in the order basic — acid — neutral amino acids. The respective amino acids alone had no effect, various Amadori compounds (fructose-alanine. -arginine and -histidine) a prooxidative effect. Extracts from roasted, defatted hazelnuts also showed correlation between browning and reducing power. Water extracts possessed higher browning and reducing power than the corresponding methanol extracts; the antioxidative effect of both extracts in ML emulsions however was comparable and increased with the roasting time as well as with the amount of extract added. The extracts were separated by gel permeation chromatography on Sephadex G-15 into three main fractions. An antioxidative effect was mainly found in the fraction of low molecular colourless Maillard reaction products.     

葡萄糖与松香胺美拉德反应产物抗氧化性能研究

通过葡萄糖与松香胺的美拉德反应可制备具有抗氧化活性的产物。研究了不同反应条件对美拉德反应产物MRPs的抗氧化性能的影响,并与常用食品抗氧化剂特丁基对苯二酚(TBHQ)进行了对比。研究表明:抗氧化能力最佳的条件是反应时间为4.5 h、温度为65℃、pH值8和葡萄糖与松香胺的物质的量之比为1:1;该条件下的产物MRPs与TBHQ的抗氧化能力接近,有望作为一种新的天然抗氧化剂。     

Purification and characterization of antioxidative peptides from protein hydrolysate of lecithin-free egg yolk

The protein extracted from lecithin-free egg yolk, normally discarded by lecithin processing plants, was hydrolyzed with the aid of Alcalase, a commercial enzyme. The hydrolysate was separated through a series of ultrafiltration membranes with molecular weight cutoffs of 10, 5, and 1 kDa; and three types of permeates including 10 K (permeate from 10 kDa), 5 K (permeate from 5 kDa), and 1 K (permeate from 1 kDa) were obtained. The antioxidative efficacy of hydrolysates so obtained was investigated and compared with α-tocopherol. Furthermore, two different peptides showing strong antioxidative activity were isolated from the hydrolysates by using consecutive chromatographic methods including ion exchange chromatography on a SP-Sephadex C-25 column, gel filtration on a Sephadex G-25 column, and high-performance liquid chromatography on an octadecylsilane column. The purity of the peptides was identified using capillary electrophoresis. The isolated peptides were composed of 10 and 15 amino acid residues, and both contained a leucine residue at their N-terminal positions.     

Optimization of antioxidant hydrolysate production from flying squid muscle protein using response surface methodology

The squid muscle protein, extracted from by-products of flying squid (Ommastrephes bartrami) was hydrolyzed by five proteases (pepsin, trypsin, papain, alcalase and flavourzyme). DPPH radical scavenging power was used to evaluate antioxidative activity of hydrolysates. The hydrolysate obtained by papain exhibited the most excellent potential of antioxidative activity. Furthermore, response surface methodology (RSM) was employed to optimize hydrolysis conditions, including enzyme to substrate (E/S) ratio, reaction temperature, and hydrolysis time. The optimum conditions obtained were as follows: E/S ratio of 1.74%, temperature of 51 °C and time of 46 min, under which, DPPH radical scavenging activity of 74.25% was obtained. Moreover, it was found that the optimum hydrolysate of 8 mg/mL displayed relatively stronger inhibitory effect on lipid peroxidation compared with α-Tocopherol of 0.1 mg/mL.     

Roasting-Related Changes in Oxidative Stability and Antioxidant Capacity of Apricot Kernel Oil

Apricot kernels were roasted for various lengths of time (0–30 min) at 180 °C and changes in the oxidative stability, antioxidant capacity, color, as well as the level of tocopherols and fatty acids of the apricot kernel oil (AKO) were monitored. While the level of tocopherols decreased, the oxidative stability and antioxidant capacity of AKO increased with roasting, probably due to the formation of antioxidative Maillard reaction products (MRPs) during the roasting. Medium roasted samples (15–20 min) were found to be more resistant to oxidative deterioration. The oil from the 30-min roasted sample was more susceptible to oxidation compared to the oil from the 20-min roasted sample in most of the stability tests. Relatively shorter roasting periods (5–10 min) also led to a decrease in oxidative stability in comparison to the unroasted sample. Brownish color and antiradical activity increased with roasting and the highest values were measured in the 30 min roasted sample.     

Enzymatic modification of sesame seed protein,sourced from waste resource for nutraceutical application

The functional characteristics which include protein solubility at different pH, emulsifying and foaming properties, degree of hydrolysis, molecular weight distribution, antioxidant and ACE inhibitory activity of sesame protein hydrolysates prepared with pepsin, papain and alcalase enzymes were evaluated. The rate of degree of hydrolysis was found to reach maximum (25–30%) within the first time fragment i.e 10 min but 80% of hydrolysis was obtained in 120 min with alcalase. SDS-PAGE of hydrolysates with papain, pepsin and alcalase evinced bands of low molecular weight protein of 14.3 kDa and even lower for alcalase treatment of 120 min. Hydrolysates so formed were of improved functional properties as evident from emulsifying and foaming property. Hydrolysis with different proteases enhanced the protein solubility significantly at pH 7.0. Antioxidative assay revealed radical scavenging activity of the hydrolysates with papain hydrolysates showing maximum antioxidative efficacy. The ultra-filtered peptide fractions which showed comparable ACE inhibitory activity were sequenced by MALDI-TOF and matched to that of previously identified ACE inhibitory peptides. The results corroborate the ACE inhibitory effect of the peptides. Hence, these highly bioactive protein hydrolysates produced from waste sesame meals can be successfully employed in various functional food formulations.     

Antioxidative action of Maillard reaction volatiles: Influence of Maillard solution browning level

Maillard reaction volatile compounds were prepared by heating a glucose-glycine solution. The antioxidant effect of the volatiles was tested in soybean oil (SBO) thermoxidation. Volatile compounds were transferred from the heated Maillard solution to the oil with a gas-tight syringe after removing the same volume of oil headspace (air). Standard accelerated oxidation was performed by heating the SBO at 90°C. Antioxidant activity was evaluated through peroxide value and headspace gas chromatographic analysis of oil volatile compounds. Furthermore, some indices, such as protection factor and oxidation kinetic rate, were used to measure the antioxidant effect. Maillard volatile effectiveness was related to browning level of glucose-glycine solution. The maximum antioxidant effect was obtained with volatiles from 12–18 hr of heating the glucose-glycine solution. This result is related to the quantity of Maillard volatiles transferred into the oil atmosphere and to the reduction power of the browned Maillard solution. Research fellow of Consejo Nacional de Investigaciones Cientificas y Tecnicas de la Republica Argentina.     

Kinetic studies of hemicellulose hydrolysis of corn stover at atmospheric pressure

The object of this work was to study the xylose production by hydrolysis of corn stover with diluted sulfuric acid at 100 °C. Several concentrations of H₂SO₄ (2%, 4% and 6% w/w) and reaction time (0–300 min) were evaluated. Kinetic parameters of mathematical models for predicting the concentrations of xylose, glucose and furfural in the hydrolysates were found. Optimal conditions for hydrolysis were 5.5% H₂SO₄ at 100 °C for 60 min; under these conditions, 86.7% of xylose yield and 2.82 g/g selectivity were attained, leading to liquors containing up to 18.73 g/l xylose, 6.64 g/l glucose and 0.63 g/l furfural. The models could be successfully used to predict the concentrations of xylose, glucose and furfural within 0–300 min under experimental acid concentrations. Furthermore, the hydrolysis process of corn stover using dilute acid could be conceived as the first stage of an integrated strategy for corn stover utilization.     

Effect of Reaction Conditions on the Volatile Pyrazines Components of Defatted Flaxseed Meal in the Maillard Reaction System

Defatted flaxseed meal, as a high-protein by-product can be used as a good raw material for the Maillard reaction (MR). A MR model system was established using glucose, fructose, and glucose/fructose (1:1) to produce volatile compounds typically obtained from defatted flaxseed meal protein hydrolysate; these compounds were analyzed using head-space solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC–MS). From the 12 MR model reaction groups, the production of pyrazines was between 12.76% and 26.56%. In the 1G group (the group prepared using DH₁ = 7.87% with a glucose concentration of 10%), the amount of pyrazines generated reached 26.56%, and this was higher than that of the other 11 model reaction groups. The effect of reaction temperature (100–150 °C), reaction time (10–60 min), and sugar concentration (5–30%) on pyrazine content was determined using the 1G group. The results of this study indicated that the effect of temperature on pyrazine production was higher than that exerted by reaction time and glucose addition. The pyrazine content reached the maximum at a reaction temperature of 140 °C. The degree of reaction and pH value were also determined; the results demonstrated that accumulation of pyrazines was suboptimal when the pH of the system was dramatically decreased. For the overall reaction, the pyrazine content remained similar to that of the final products; however, the pyrazine content exhibited little correlation with the intermediate products in the MR.     

Antioxidative and Functional Properties of Pumpkin Oil Cake Globulin Hydrolysates

Cucurbitin extracted from pumpkin (Cucurbita pepo) oil cake was enzymatically hydrolysed with three different enzymes viz. alcalase, flavourzyme and pepsin. Antioxidative and functional properties of cucurbitin hydrolysates with different degrees of hydrolysis (DH) were investigated. The antioxidant activity of the hydrolysates was strongly dependent on the enzyme used. The hydrolysates obtained by alcalase and pepsin showed antioxidative potential whereas flavourzyme hydrolysates did not demonstrate these activities. Reducing power and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) scavenging activity of cucurbitin hydrolysate were positively related to DH. The highest antioxidant activity was found in the hydrolysate obtained by alcalase at DH 25.6 % [reducing power of 0.25 ± 0.01 A700 nm and ABTS scavenging activity of 3.34 ± 0.02 mmol/L Trolox equivalent antioxidant coefficients (TEAC)]. Hydrolysis by all enzymes increased the protein solubility within the studied pH range. The best emulsion activity and stability index (EAI = 143.28 ± 3.05 m²/g and ESI = 87.5 ± 1.96 min) have hydrolysates produced by flavourzyme (DH 9.2 %) whereas alcalase produced hydrolysates with the best foaming capacity (FC = 242 ± 3.21). The results demonstrate that hydrolysates produced in the present study have good functional properties as well as antioxidant activity indicating their possible use in different food systems.     

Enzymatic synthesis of acetylated glucose fatty acid esters in organic solvent

Two immobilized lipases fromCandida antarctica (SP 382) andC. cylindraceae, nowrugosa (2001), catalyzed the synthesis of novel acetylated glucose fatty acid esters with glucose pentaacetate (GP) and Trisun 80 (80% oleic) vegetable oil or methyl oleate as substrates in organic solvents. The relative yield was between 6.4–52%, and the incorporation of oleic acid onto the glucose was between 31–100%. In addition, these enzymes were able to catalyze the synthesis of glucose fatty acid esters with free glucose as the sugar substrate. The highest oleic acid incorporation (100%) was obtained in benzene with SP 382 lipase and Trisun 80 as the acyl donor. With methyl oleate as the acyl donor, greater incorporation was obtained in benzene (90.5%) compared to 75% in isooctane. The 2001 lipase was better in benzene/pyridine (2∶1 vol/vol) 74%) and chloroform (61%) compared to benzene and isooctane. However, with free glucose and Trisun 80 as substrates, both enzymes gave acceptable levels of oleic acid incorporation (82–100%) in benzene, benzene/pyridine and pyridine. The best conditions for the ester interchange reaction reported are: lipase (10% by weight of substrate); incubation time 48 h; molar ratio of Trisun/GP 1∶2; 3 mL solvent and 3% added water. These glucose esters have potential applications as emulsifiers in food, cosmetics and pharmaceutical formulations.     

Purification and crystallization of xylitol from fermentation broth of corncob hydrolysates

Xylitol, a five-carbon sugar alcohol, is a valuable sugar substitute, and widely used in the pharmaceutical, odontological and food industry due to its interesting properties. In the past decades, the xylitol industry has grown rapidly and more attention has been focused on xylitol purification, which possesses an important proportion of the whole industry. In our paper, the purification and crystallization of xylitol fermentation broth by biotechnology using corncob hydrolysates as substance were studied. An initial xylitol fermentation broth was decolored with activated carbon (1% M-1, 60°C, 165rpm), desalted with a combination of two ion-exchange resins (732 and D301), and residual sugars were separated with UBK-555(Ca²⁺). Then the solution was vacuum-concentrated up to supersaturation (750g/L xylitol). After adding 1% xylitol crystal seeds, the supersaturated solution was cooled to −20°C for 48h. The crystalline xylitol of a regular tetrahedral shape with purity 95% and crystallization yield 60.2% was obtained from the clarified xylitol fermentation broth. An intact, economical and environmental-friendly route of purification and crystallization of xylitol from fermentation of corncob hydrolysates was obtained, and its experimental procedure and data provided a sound basis for large-scale industrial production.     

Antioxidant activity of pea bean (Phaseolus vulgaris L.) extract

Antioxidative activity of pea bean (Phaseolus vulgaris L.) extract was evaluated by using a linoleic acid system, and the methanol extract exhibited strong antioxidative activity as measured by the thiocyanate method. The crude methanol extract was partitioned between then-butanol phase (BP) and the water phase (WP). Then, the antioxidative activity of the BP and the WP was determined by using a linoleic acid system. The WP showed strong antioxidative activity, while BP showed only weak activity as measured by the thiocyanate method. Next, the synergistic antioxidative action of WP with α-tocopherol was examined by using linoleic acid and liposome systems. The WP had a synergistic effect with α-tocopherol in both the food model and liposome systems. For purification and isolation of the antioxidative substances of the pea bean, preparative high-performance liquid chromatography was carried out with an octadecylsilyl column. Five fractions were collected, and antioxidative activity was determined in a linoleic acid system. Although fraction 1 had strong activity by the thiocyanate method, the purification of this active fraction was difficult; therefore, the partly characterized active fraction was investigated. The contents of total phenolics and sugars were 0.31±0.01 mg/g of fraction 1 and 406.1±0.1 mg/g, respectively. The ninhydrin chromogenic reaction was positive, and the ultraviolet absorption spectral λ max value in distilled water was 264.0 nm, indicating that the water-soluble antioxidative components from pea bean may be a new type of antioxidant. Isolation and identification are currently being investigated.     

Oxidation products of cyanidin 3-O-β-d-glucoside with a free radical initiator

Recently, we have reported that anthocyanins show strong antioxidative activity, but no attention has been paid to anthocyanins from the viewpoint of the reaction mechanism of alkylperoxyl radicals; therefore, we investigated the reaction products of antioxidative anthocyanins (cyanidin 3-O-β-d-glucoside). Cyanidin 3-O-β-d-glucoside was reacted with 2,2′-azobis(2,4-dimet hylvaleronitrile) to generate the alkylperoxyl radicals, and the reaction products were isolated by high-performance liquid chromatography. The products were identified as 4,6-dihydroxy-2-O-β-d-glucosyl-3-oxo-2,3-dihydrobenzofuran and protocatechuic acid. Based on reaction products, the antioxidative mechanism of cyanidin 3-O-β-d-glucoside may be different from that of α-tocopherol; cyanidin 3-O-β-d-glucoside would produce another radical scavenger, as it would break down the structure and scavenge the radicals.     

Optimization of the Aqueous Enzymatic Extraction of Rapeseed Oil and Protein Hydrolysates

An aqueous enzymatic extraction method was developed to obtain free oil and protein hydrolysates from dehulled rapeseeds. The rapeseed slurry was treated by the chosen combination of pectinase, cellulase, and β-glucanase (4:1:1, v/v/v) at concentration of 2.5% (v/w) for 4 h. This was followed by sequential treatments consisting of alkaline extraction and an alkaline protease (Alcalase 2.4L) hydrolysis to both produce a protein hydrolysate product and demulsify the oil. Response surface methodology (RSM) was used to study and optimize the effects of the pH of the alkaline extraction (9.0, 10.0 and 11.0), the concentration of the Alcalase 2.4L (0.5, 1.0 and 1.5%, v/w), and the duration of the hydrolysis (60, 120, and 180 min). Increasing the concentration of Alcalase 2.4L and the duration of the hydrolysis time significantly increased the yields of free oil and protein hydrolysates and the degree of protein hydrolysis (DH), while the alkaline extraction pH had a significant effect only on the yield of the protein hydrolysates. Following an alkaline extraction at pH 10 for 30 min, we defined a practical optimum protocol consisting of a concentration of 1.25–1.5% Alcalase 2.4L and a hydrolysis time between 150 and 180 min. Under these conditions, the yields of free oil and protein hydrolysates were 73–76% and 80–83%, respectively. The hydrolysates consisted of approximately 96% of peptides with a MW less than 1500, of which about 81% had a MW less than 600 Da.     

Downstream Processes for Aqueous Enzymatic Extraction of Rapeseed Oil and Protein Hydrolysates

Downstream processes following aqueous enzymatic extraction (AEE) of rapeseed oil and protein hydrolysates were developed to enhance the oil and protein yields as well as to purify the protein hydrolysates. The wet precipitate (meal residue) from the AEE was washed with twofold water at 60 °C, pH 11 for 1 h. Emulsions from the AEE and the washing step were pooled and submitted to a stepwise demulsification procedure consisting of storage-centrifugation and freezing–thawing followed by centrifugation. Aqueous phases were pooled and adsorbed onto macroporous adsorption resins (MAR) to remove salts and sugars. Following extensive rinsing with deionized water (pH 4), desorption was achieved by washing with 85% ethanol (v/v) to obtain crude rapeseed peptides (CRPs). In a separate experiment, stepwise desorption was carried out with 25, 55, and 85% ethanol to separate the bitter peptides from the other peptides. Using a combination of the AEE process, washing and demulsification steps, the yields of the total free oil and protein hydrolysates were 88–90% and 94–97%, respectively. The protein recovery was 66.7% and the protein content was enriched from 47.04 to 73.51% in the CRPs. No glucosinolates and phytic acid were detected in the CRPs. From the stepwise desorption, a non-bitter fraction RP25 (containing 64–66% of total desorbed protein) had a bland color and significantly higher protein content (81.04%) and hence was the more desirable product.     

Effect of Long-Term Dietary Arginyl-Fructose (AF) on Hyperglycemia and HbA1c in Diabetic db/db Mice

We have previously reported that Amadori compounds exert anti-diabetic effects by lowering sucrose-induced hyperglycemia in normal Sprague-Dawley rats. In the present study we extended our recent findings to evaluate whether α-glucosidase inhibitor arginyl-fructose (AF) lowers blood glucose level in diabetic db/db mice, a genetic model for type 2 diabetes. The db/db mice were randomly assigned to high-carbohydrate diets (66.1% corn starch) with and without AF (4% in the diet) for 6 weeks. Changes in body weight, blood glucose level, and food intake were measured daily for 42 days. Dietary supplementation of AF resulted in a significant decrease of blood glucose level (p < 0.001) and body weight (p < 0.001). The level of HbA1c, a better indicator of plasma glucose concentration over prolonged periods of time, was also significantly decreased for 6-week period (p < 0.001). Dietary treatment of acarbose^® (0.04% in diet), a positive control, also significantly alleviated the level of blood glucose, HbA1c, and body weight. These results indicate that AF Maillard reaction product improves postprandial hyperglycemia by suppressing glucose absorption as well as decreasing HbA1c level.     

Effect of Drying Methods on Odorous Compounds and Antioxidative Activity of Gelatin Hydrolysate Produced by Protease from B. amyloliquefaciens H11

Gelatin hydrolysates with antioxidative activity produced by protease from Bacillus amyloliquefaciens H11 with different hydrolysis times were prepared. Alpha-amino group content and antioxidative activities increased with increasing hydrolysis time (p < 0.05). When gelatin hydrolysate prepared with hydrolysis time of 3 h (GH-3H) was subjected to freeze drying and spray drying, the powder obtained from spray drying showed a decrease in antioxidant activity as measured by DPPH and ABTS radical scavenging activities, ferric-reducing antioxidant power, and metal chelating activity. Spray-dried gelatin hydrolysate (GH-3H-SD) showed higher whiteness with lower fishy odor and off-odor associated with fermentation. This was concomitant with the decreases in several odorous compounds in the sample, except for nonanal, which was higher in comparison with the powder obtained by freeze drying. Thus, spray drying could be an effective drying method to improve color and reduce undesirable odor of gelatin hydrolysate.