不同分子质量大豆蛋白和鸡肉酶解物的美拉德反应产物风味特征分析

为了研究不同分子质量的肽在美拉德反应后的风味特征,以大豆蛋白和鸡肉为原料酶解得到蛋白酶解物。对酶解物超滤分离得到小于1000Da、1000~5000Da和大于5000Da的不同分子质量肽组分,并对大豆蛋白和鸡肉酶解物完全酸水解得到复合氨基酸。在得到的肽段和氨基酸中添加一定量的木糖,构建美拉德反应模型。对美拉德反应产物感官特性进行评价,再采用气相色谱-质谱联用、高效液相色谱对挥发性和不挥发性化合物进行分析。结果表明:在2种不同蛋白来源的酶解物的美拉德反应产物中,共鉴定出挥发性化合物69种,其中吡嗪和呋喃硫醇等肉香味化合物的含量最高。统计分析表明:不同分子质量的肽和游离氨基酸的挥发性化合物存在明显差异。小于1000Da的肽在美拉德反应过程促进了吡嗪类化合物的生成,其中包括了吡嗪、5-甲基-2-乙基吡嗪、2,5-二甲基-3-乙基吡嗪、三甲基吡嗪、2-乙酰基吡咯等挥发性化合物。与肽相比,游离氨基酸有利于含硫化合物如呋喃硫醇类和噻吩类物质的生成。有29种挥发性化合物的相对气味活性值大于1。偏最小二乘回归研究了气味化合物与感官评价之间的相关性,发现小于1000Da的肽与基本的肉味和浓厚味密切相关,而大于5000Da的肽与苦味和焦煳味密切相关。在美拉德反应后,分子质量大于5000Da的肽数量显著减少；分子质量1000~5000Da的肽降解可以补充消耗的游离氨基酸；分子质量小于1000Da的肽容易发生交联和聚合现象而含量增加,其产物对风味的影响明显增强,能更好地体现基本的肉味、鲜味和浓厚味。希望研究可以为利用蛋白质酶解物生产美拉德反应产物的应用提供理论支撑和指导。     

Temperature effect on the non-volatile compounds of Maillard reaction products derived from xylose–soybean peptide system: Further insights into thermal degradation and cross-linking

Solutions of soybean peptide with or without xylose were heated over a range of temperatures (80–130 °C) for 2 h to investigate the characteristics of Maillard reaction and the effect of temperature on amino acids and peptides. It was found that both peptide degradation and peptide cross-linking occurred in the Maillard reaction. The critical temperature for peptide degradation was 100 °C, and above it, peptides degraded quickly in thermal degradation system. However, in Maillard reaction system, peptides cross-linked rapidly when the temperature reached 110 °C. Bitter amino acids and peptides below 1000 Da decreased 18.44% and 28.49%, respectively, after Maillard reaction at 120 °C. On the other hand, peptides between 1000 and 5000 Da were increased significantly, nearly doubled compared to its initial hydrolysates after Maillard reaction at 120 °C. Moreover, the increase of macromolecule products was also accompanied with severe browning and pH decrement.     

Taste properties of Maillard-reaction products prepared from 1000 to 5000 Da peptide

This study investigated the flavour-enhancing properties of the Maillard reaction products from 1000 to 5000 Da peptides. Protein hydrolyzates obtained from enzymatic hydrolysis of soybean protein were fractionated with UF membranes to obtain the 1000–5000 Da fraction. Xylose was added to this fraction and allowed to react for 3.5 h at 95 °C. This reaction mixture was fractionated with 1000 and 5000 Da cut off membranes to obtain the 1000–5000 Da fraction (the “Maillard peptide”). To evaluate the flavour characteristics of the Maillard peptide, an additional test on a umami solution was carried out. It was found that the Maillard peptide produced an enhanced effect on flavour, including umami, continuity and mouthfulness in the umami solution and in consommé soup.     

Purification and identification of kokumi-enhancing peptides from chicken protein hydrolysate

The Maillard reaction products (MRPs) from chicken protein hydrolysate were demonstrated to have intense umami and kokumi-enhancing effects. To find the main flavour-enhancing compounds in the chicken protein hydrolysate, the fractions with different molecular weights were obtained by ultrafitration. The evaluation of taste characteristics revealed that the fractions with molecular weights ranging from 1000 to 5000 Da predominantly contributed to the umami and kokumi-enhancing effects. After further purification by using ultrafiltration, gel filtration chromatography, and ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) in combination with sensory evaluation, three peptides were identified, an octapeptide (WVNEEDHL), a nonapeptide (NSLEGEFKG) and a decapeptide (KDLFDPVIQD). Sensory evaluation results showed that all three peptides could significantly enhance the meat flavour, umami taste and thickness of the chicken powder solution. The results indicate that the peptides have potential application as effective chicken flavour-enhancing ingredients in the food industry.     

Effect of Maillard reaction products derived from the hydrolysate of mechanically deboned chicken residue on the antioxidant,textural and sensory properties of Cantonese sausages

Protein hydrolysates as precursors of Maillard reaction were obtained via enzymatic hydrolysis of mechanically deboned chicken residue (MDCR). The Maillard reaction products (MRPs) were prepared at 90 (M1), 100 (M2), 110 (M3) and 120 °C (M4), respectively. MRPs possessed a strong reducing power and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity. According to the evolution of total free fatty acids and peroxide value of Cantonese sausage with MRPs during storage, M1 and M3 had a potent antioxidant activity (P < 0.05) due to their antioxidant abilities and inhibitory action against lipolytic enzymes. Cantonese sausages treated with M1 and M2 showed good textural and sensory properties. However, M3 and M4 had a negative (P < 0.05) effect on the flavour and texture of Cantonese sausages compared to control. The results suggested that M1 was very potential to be used to improve their antioxidant, textural and sensory quality.     

Enzymatic hydrolysates from tuna backbone and the subsequent Maillard reaction with different ketohexoses

Enzymatic hydrolysates from tuna backbone were prepared, and the subsequent Maillard reaction with rare sugars (d ‐psicose, d ‐sorbose and d ‐tagatose) was investigated. The hydrolysates were found to contain a large number of short peptides under 1000 Da and were good sources of essential amino acids. In assays of free radical scavenging activity and reducing power, the Maillard reaction products from rare sugars, especially d ‐tagatose, performed better than that from d ‐fructose. After heating at 55 °C for 48 h, the scavenging capacity of the hydrolysates for 1,1‐diphenyl‐2‐picryl‐hydrazyl radicals improved by 8.9‐ and 16‐fold in the presence of d ‐fructose and d ‐tagatose. Hence, hydrolysates with high nutrient contents could be prepared from fish by‐products via proteolysis, and the Maillard reaction of rare sugars may greatly promote the antioxidant activity of the hydrolysates.     

Effect of angiotensin I converting enzyme inhibitory peptide purified from skate skin hydrolysate

Our objective was to evaluate the angiotensin I converting enzyme (ACE) inhibitory activity of skate skin protein hydrolysates and its corresponding fractions. The skate skin hydrolysates were obtained by enzymatic hydrolysis using alcalase, α-chymotrypsin, neutrase, pepsin, papain, and trypsin. Amongst the six hydrolysates, the α-chymotrypsin hydrolysate had the highest ACE inhibitory activity compared to other hydrolysates. The amino acid sequences of the purified peptides were identified to be Pro–Gly–Pro–Leu–Gly–Leu–Thr–Gly–Pro (975.38 Da), and Gln–Leu–Gly–Phe–Leu–Gly–Pro–Arg (874.45 Da). The purified peptides from skate skin had an IC₅₀ value of 95 μM and 148 μM, respectively, and the Lineweaver–Burk plots suggest that they act as a non-competitive inhibitor against ACE. Our study suggested that novel ACE inhibitory peptides derived from skate skin protein may be beneficial as anti-hypertension compounds in functional foods.     

Purification of antioxidative peptides prepared from enzymatic hydrolysates of tuna dark muscle by-product

To produce and identify bioactive peptides, two commercial enzymes, orientase (OR) and protease XXIII (PR) were used to hydrolyze tuna dark muscle by-product for up to 6 h, and the hydrolysates were evaluated for antioxidative properties. The results showed that, 60-min OR and 120-min PR hydrolysates possessed the highest antioxidative activity. Then, the protein hydrolysates were subjected to a Sephadex G-25 gel filtration chromatography, and the molecular weight of the peptide fractions which showed the highest antioxidative activity ranged from 390 to 1400 Da. The peptide fractions were further isolated using the two-step high-performance liquid chromatography (HPLC-1 and HPLC-2), and the amino acid sequences of the two antioxidative peptides from OR and PR hydrolysates were Leu–Pro–Thr–Ser–Glu–Ala–Ala–Lys–Tyr (978 Da) and Pro–Met–Asp–Tyr–Met–Val–Thr (756 Da), respectively. We thus conclude that antioxidative hydrolysates from tuna dark muscle by-product may be useful ingredients in food and nutraceutical applications.     

Antioxidant and biochemical properties of protein hydrolysates prepared from Silver carp (Hypophthalmichthys molitrix)

The antioxidant and biochemical properties of enzymatically hydrolyzed silver carp (Hypophthalmichthys molitrix) protein were studied. The molecular weight of the main peaks of the hydrolysates by both Alcalase and Flavourzyme was lower than 5000 Da. The hydrolysates treated by Alcalase for ?1.5 h (hydrolysis time) showed that the relative proportion of <1000 Da fraction was more than 60%. For the biochemical properties, hydrolysis by both enzymes increased protein solubility to above 75% over a wide pH range; and when the hydrolysis time was prolonged (>3 h), the colour of the hydrolysates turned yellowish. The protein hydrolysates exhibited significant hydroxyl radical-scavenging activity and inhibited linoleic acid peroxidation. For Alcalase treatment, the hydroxyl radical-scavenging activity and the inhibition of linoleic acid peroxidation of hydrolysates appeared to reach a maximum level for 1.5, 2.0 h of hydrolysis, respectively; and their antioxidant activity was close to that of α-tocopherol in a linoleic acid emulsion system, and carnosine in the 2-deoxyribose oxidation system. The hydrolysate with lower molecular weight distribution possessed stronger Fe²⁺ chelation ability at a sample concentration of 5.0 mg/mL. The results suggested that the antioxidant activity of silver carp protein hydrolysates were related to its degree of hydrolysis (DH), hydrolysis time and molecular weight.     

Taste enhancer from the long-term ripening of miso (soybean paste)

Long-term ripened miso has a characteristic mouthfulness and continuity of flavour, which is heightened from 11 months of ripening. Focussing on its main components, changes of protein and sugar were investigated from 10 days up to 20 months of ripening. Protein and sugar changes during ripening did not correlate with sensory evaluation results. From visual observation of miso colour and colorimetric analysis of the water-soluble fraction, it was apparent that the Maillard reaction was occurring during 5–11 months of ripening. By fractionation and evaluation of umami, mouthfulness and continuity, we were able to identify a water soluble fraction of 20 month ripened miso with a molecular weight of 1000–5000 which was coloured and appeared to be a peptide that has undergone the Maillard reaction. From these results, the Maillard-reacted peptide was considered to be a key substance which gives the characteristic flavour (mouthfulness and continuity) of long-ripened miso.     

Characteristics and antioxidant activity of ultrafiltrated Maillard reaction products from a casein–glucose model system

Maillard reaction products (MRPs) were prepared from casein–glucose by refluxing for 130 min at 102 °C and initial pH 12.0 without pH control to investigate the characteristics of casein–glucose Maillard reaction and the antioxidant activity difference among different fractions of MRPs. Browning and intermediate products increased, however, the pH of the system decreased with increase in the heating time. Free amino group content decreased 78% during first 10 min and did not change nearly thereafter. Amino acid analysis indicated that lysine and arginine decreased significantly, and casein was partially hydrolysed to peptides or free amino acid. High molecular weight compounds were dominant in the MRPs, determined by high performance gel-filtration chromatography. After ultrafiltration, antioxidant activity of each MRPs fraction was investigated by DPPH radical-scavenging activity, reducing power, Fe²⁺ chelating activity and lecithin oxidation assay. MRPs of different molecular weight exhibited distinctly different antioxidant activities.     

Influence of technological processes on phenolic compounds,organic acids,furanic derivatives,and antioxidant activity of whole-lemon powder

The healthy properties of citrus fruits have been attributed to ascorbic acid and phenolic compounds, mainly to flavonoids. Flavonoids are important phytonutrients because they have a wide range of biological effects that provide health-related properties. In this context, this study seeks to characterise the phenolic compounds in lemon and their stability in different drying processes (freeze-drying and vacuum-drying) and storage conditions (−18 and 50 °C for 1 and 3 months). A powerful high-performance liquid chromatography coupled to DAD and electrospray-ionization time-of-flight mass spectrometry (HPLC–ESI-TOF-MS) method has been applied for the separation, identification, and quantification of 19 phenolic compounds and 4 organic acids. To our knowledge, two hydroxycinnamic acids have been identified for the first time in lemon. Folin–Ciocalteu was applied to determine total phenolic compounds and TEAC, FRAP, and ORAC were applied to determine the antioxidant capacity of lemon. Total phenolic content significantly differed in the samples analysed, vacuum-dried lemon showing the highest phenolic content, followed by freeze-dried lemon and, finally, vacuum-dried lemon stored at 50 °C for 1 and 3 months. The content in furanic compounds was determined to evaluate the heat damage in lemon and it was showed an increase with the thermal treatment because of the triggering of Maillard reaction. As exception of ORAC, antioxidant-capacity assays were not correlated to phenolic content by HPLC due to the formation of antioxidant compounds during Maillard reaction.     

Preparation and characterisation of isoflavone aglycone‐rich calcium‐binding soy protein hydrolysates

Isoflavone aglycone‐rich calcium‐binding soy protein hydrolysates were prepared by subcritical water treatment and subsequent protease hydrolysis. Contaminated β‐glucosidase in the Protease M preparation could effectively convert glycosides into aglycones. Compared with Alcalase hydrolysates, Protease M hydrolysates exhibited higher molecular weight (>5000 Da) and more hydrophobic characteristics because of its weaker proteolytic activity. The antioxidant activity of Protease M hydrolysates was obviously improved. Initial increased DPPH and ABTS radical scavenging rate of Protease M hydrolysates may be ascribed to the conversion of isoflavones (<30 min) and a gradual release of antioxidant peptides. In the later hydrolysis, a gradual exposure of isoflavones involved in the interior of heat‐induced protein aggregates was mainly responsible for further improved antioxidant activities. Higher calcium‐binding capacity (up to 7.86%) with lower yield of peptide–calcium complex was observed for Protease M hydrolysates. These results could help researchers to develop a feasible protocol for producing nutrient‐enhanced soy protein hydrolysates.     

Influence of salt and pH on the solubility and structural characteristics of transglutaminase-treated wheat gluten hydrolysate

Hydrolyzed wheat gluten (GH, 77–85% protein) was prepared by limited chymotrypsin digestion at 37 °C for 4 h (degree of hydrolysis = 6.4%) and 15 h (degree of hydrolysis = 10.3%). Microbial transglutaminase (MTGase) treatment (55 °C for 1 h, or 5 °C for 18 h) effect on the solubility and structural characteristics of GH was examined under selected food processing conditions (pH 4.0–7.0, 0–0.6 M NaCl). The MTGase treatment increased solubility of GH by 3–29-fold (P < 0.05) within pH 4.0–7.0. Addition of 0.6 M NaCl or changing the conditions of MTGase incubation did not significantly alter solubility characteristics of GH. The MTGase treatment decreased surface hydrophobicity, and increased carboxyl groups in GH, suggesting cross-linking and deamidation. Fluorescence and UV spectra attributed the improved GH solubility to MTGase-induced polar environment, and partial masking of some nonpolar aromatic amino acids possibly due to high-molecular-weight polypeptides formed.     

酶法及美拉德反应改进鸡肉蛋白功能性质的研究

利用不同单酶酶解鸡胸肉,制得的酶解液和木糖进行美拉德反应,考察不同酶解方式制得的底物对美拉德反应产物的各检测指标(肽、氨基酸、糖等反应底物含量和美拉德产物含量及其抗氧化性能力)影响,并分析各检测指标间的相关性。实验表明:酶解程度对美拉德反应产物特性有显着性影响,酶解作用所得的肽具有更强的美拉德反应活性,酶解程度越大的酶解液,消耗糖量越多,生成的MRPs越多,其MRPs抗氧化活性越强,同一反应起始浓度,8 h与2 h酶解液的MRPs抗氧化能力相比,FRAP还原能力与DPPH·清除能力增强倍数高达2倍和7倍;美拉德反应能明显改善了酶解液的性质,可溶解性肽的含量最高增加了2倍,可溶性氨基酸最高增加了1倍,抗氧化能力最高增强了40倍;从检测指标的相关性可知,糖的消耗量变化一定程度上能反应美拉德反应的程度,美拉德反应能促进肽的分解生成氨基酸。     

Characterization of antioxidant activity and volatile compounds of Maillard reaction products derived from different peptide fractions of peanut hydrolysate

Five peptide fractions isolated from peanut hydrolysate were purified by ultrafiltration and gel filtration chromatography. Their reaction degrees with glucose or lecithin in Maillard reaction were compared. Glucose consumption, oxygen radical absorbance capacity (ORAC) values and volatile compounds composition of peanut hydrolysate (PH) and its peptide fractions after thermal treatment and Maillard reaction were evaluated. Results revealed that the peptide fraction of 1-3 kDa showed the highest antioxidant activity. The peptides with smaller molecular weight showed a higher reaction degree to increase antioxidant activity and to produce more volatile compounds through Maillard reaction. Analysis of molecular weight distribution showed that peptide degradation and cross-linking simultaneously occurred during the Maillard reaction. In addition, lecithin addition to peptide-glucose system caused a significant increase of antioxidant activity possibly due to more nitrogen-containing compounds formed.     

草鱼抗氧化肽的美拉德反应特性研究

本研究通过单独加热草鱼肽和添加木糖加热反应制备热降解产物（TDPs）和美拉德反应产物（MRPs),运用DPPH?抑制率、肽分子量分析及氨基酸分析等方法评价不同反应时间草鱼肽热降解产物及美拉德反应产物的抗氧化性能、分子量分布以及氨基酸组成的变化规律,深入探讨了反应时间对草鱼肽的美拉德反应产物特性的影响。研究发现,单独加热草鱼肽对各时间段热降解产物的总氨基酸含量无显著影响,游离氨基酸含量显著增加,而3000 Da以下肽段含量增多。美拉德反应体系样品随着反应时间的增加,产物中总氨基酸及游离氨基酸含量下降,其中精氨酸及赖氨酸减少尤其显著,分子量大于3000 Da的肽段明显增多,3000 Da以下的肽段含量降低,此外,美拉德反应产物中抗氧化活性显著增强。     

Characteristic and antioxidant activity of retorted gelatin hydrolysates from cobia (Rachycentron canadum) skin

Alkali-pretreated cobia (Rachycentron canadum) skin was extracted in a retort (121 °C) for 30 min to obtain a retorted skin gelatin hydrolysate (RSGH). The molecular mass distributions and antioxidant activities of cobia RSGH and enzyme-treated RSGHs (ET-RSGHs) derived from bromelain, papain, pancreatin, and trypsin digestion were then characterized. The molecular mass distribution of the RSGH ranged mainly between 20,000 and 700 Da and those of ET-RSGHs ranged between 6500 and 700 Da. The DPPH (α,α-diphenyl-β-picrylhydrazyl) radical scavenging effects (%) of 10 mg/ml of RSGH and 10 mg/ml of the four ET-RSGHs were 55% and 51–61%, respectively. The lipid peroxidation inhibition (%) of RSGH and ET-RSGHs (10 mg/ml) were 58% and 60–71% on the fifth day in a linoleic acid model system, respectively. The 3Kd-ET-RSGHs, obtained by using a series of centrifugal ultrafiltration filters (molecular weight cut-offs of 10, 5, and 3 kDa done sequentially with decreasing pore size), exhibited dramatically improved antioxidant activity, with most of the molecular mass ranging below 700 Da. Compared to 10 mg/ml of the RSGH, 10 mg/ml of 3Kd-ET-RSGHs exhibited 45–65% more scavenging of DPPH radical and 24–38% more inhibition of lipid peroxidation. The peptides with molecular masses below 700 Da in the ET-RSGHs or 3Kd-ET-RSGHs significantly affect the antioxidant properties. These peptides are composed of a small number of amino acids or free amino acids and have the potential to be added as antioxidants in foods.     

Comparative study of antioxidant and flavour characteristics of Maillard reaction products from five types of protein hydrolysates

Antioxidant, structural, and flavour characteristics of Maillard reaction products (MRPs) prepared from different hydrolysates of sweet potato protein (SPPH), potato protein (PPH), soy protein isolate (SPIH), egg white protein (EWPH), and whey protein isolate (WPIH) were compared. WPIH-MRPs exhibited the highest Maillard reaction (MR) progress followed by SPPH-MRPs as indicated by the lowest pH (4.95 and 5.10, respectively) and the highest fluorescence intensity (P < 0.05). The results of Fourier transform infrared (FTIR) explained the significant changes in functional groups of peptides after MR, especially in WPIH-MRPs and SPPH-MRPs. The highest oxygen radical absorbance capacity (ORAC) of 125.24 µg TE (Trolox equivalents)/mL was observed for WPIH-MRPs, followed by SPPH-MRPs with an ORAC value of 104.07 µg TE/mL (P < 0.05). MR conferred an increase of sweetness, sourness, and umami attributes and reduction of bitterness for all MRPs, and WPIH-MRPs presented the highest umami taste score of 7.4, followed by SPPH-MRPs with a taste score of 7.1. Stronger umami taste was correlated with MW 200–500 and <200 Da peptides. No acrylamide was detected in SPPH-MRPs, which also presented less 5-hydroxymethyl furfural (HMF) and Nε-(1-Carboxymethyl)-L-lysine (CML) compared to WPIH-MRPs. Thus, MRPs derived from SPPH could be an alternative way for natural flavours’ production with improved antioxidant activity and less harmful compounds.     

Antioxidant activity of hydrolysates obtained from scallop (Patinopecten yessoensis) and abalone (Haliotis discus hannai Ino) muscle

Scallop (Patinopecten yessoensis) and abalone (Haliotis discus hannai Ino) muscle were hydrolysed with commercially available food-grade proteases. The resulting hydrolysates showed DPPH and hydroxyl radicals scavenging abilities, reducing power, and ferrous ion chelating capacity. The antioxidant activities of hydrolysate of abalone foot muscle (HAFM) increased with increasing incubation time during the whole hydrolysis process in 180 min. Whereas, the antioxidant activities of hydrolysate of scallop adductor muscle (HSAM) increased at initial stage and peaked after 25-30 min of hydrolysis, and then gradually decreased thereafter. Compared with HAFM, HSAM with comparable hydrolysis time contained more free amino acids (FAA) and small-sized peptides (below 500 Da), which may account for the differences in antioxidant activities versus hydrolysis time curves of the two hydrolysates. The above results indicate that limited hydrolysis of proteins can increase their antioxidant activity, whereas extensive hydrolysis can decrease it.