甜菜果胶乳化活性及稳定性

甜菜果胶是一种从甜菜粕中提取的酸性阴离子多糖,主链由鼠李糖和半乳糖醛酸组成,侧链数量丰富,主 要由鼠李糖、阿拉伯糖、半乳糖、果糖等一些中性糖组成。其中中性糖末端与蛋白质共价连接,赋予了甜菜果胶 良好的乳化性质。本研究主要探究了甜菜果胶的乳化特性并与柑橘果胶进行对比。考察了甜菜粕产地、果胶质量 浓度、pH值、温度、贮藏时间等对乳液特性（粒径分布、平均粒径、Zeta-电位和浊度变化）的影响。研究结果表 明,产地不同对甜菜果胶结构组成影响较大,以甜菜果胶制备的乳液粒径显著小于柑橘果胶乳液,且乳化活性更 高。当甜菜果胶质量浓度为10～25 mg/mL时,乳液在4 周的贮存期内保持良好的稳定性,而柑橘果胶乳液粒径显著 增加。pH 2～6的范围内,果胶粒径基本保持不变。25～85 ℃升温过程中,柑橘果胶乳液粒径大幅增加。说明甜菜 果胶具有良好的乳化活性和稳定性。本研究为甜菜果胶的实际应用提供了理论指导。     

Optimisation of production yield by ultrasound‐/microwave‐assisted acid method and functional property of pectin from sugar beet pulp

Response surface methodology was used to optimise pectin recovery from sugar beet pulp using ultrasound‐/microwave‐assisted acid method (UMAAM). The independent variables were microwave heating temperature, microwave heating time and solid‐to‐liquid ratio. From the results, the selected optimal conditions were 92 °C, 37 min, and solid‐to‐liquid ratio 1:30. Under these conditions, the yield and uronic acid content of the pectin (SBP1) was 26.16% and 75.38%, respectively. Compared with the sugar beet pectin (SBP2) extracted by traditional acid method, SBP1 showed a higher molecular weight, higher viscosity and emulsifying activity and stability. The possible reason was that the UMAAM could have had minimal change in the protein–polysaccharide complex structure of pectin, but significantly increased the length of polysaccharide chains compared with SBP2. These results suggested that UMAAM is an efficient method in extracting pectin and has the potential to be used in the sugar beet industry.     

The Emulsifying and Emulsion‐Stabilizing Properties of Pectin: A Review

Pectin, a plant cell wall polysaccharide, is a natural multifunctional ingredientwhich imparts textural and rheological properties to a wide range of food systems. Up to the last decade, most pectin blank applications stemmed from its gel‐forming ability. Nowadays, pectin is gradually gaining acceptance as an effective emulsifier in numerous food applications. Accordingly, the emulsifying and emulsion‐stabilizing properties of this hydrocolloid are increasingly being assessed. These pectin functionalities are controlled by both the properties of the carbohydrate moieties and of the often attached protein groups. Generally, the protein moiety, feruloyl, and acetyl groups, play a major role in pectin emulsifying activities, while the emulsion‐stabilizing properties of the polymer are controlled by the homogalacturonan (HG) domain and the neutral sugar side chains of the rhamnogalacturonan‐I (RGI) structural element. However, the neutral sugar side chains might obstruct the accessibility of pectin hydrophobic species to the oil/water interface, thereby hampering emulsification. In addition, the contribution of HG to emulsion stabilization might be dependent on the polymer HG:RGI ratio. Hence, the influence of pectin structural features on the polymer emulsifying potentials is yet to be fully unraveled, as identified in this review. Furthermore, the emulsifying and emulsion‐stabilizing properties of pectin are influenced by the composition of emulsions.     

Emulsification properties of sodium caseinate‐based conjugates with selected polysaccharides

Sodium caseinate (SC) was conjugated with polysaccharides, viz. maltodextrin (MD), pectin (P) and gum arabic (GA) at protein:polysaccharide weight ratio of 1:2, 1:1 and 2:1. The emulsifying properties and other relevant chemical properties of these conjugates were compared. The visible colour change, SDS‐PAGE analysis and available reducing groups confirmed greater conjugation in SC‐MD conjugate than the SC‐GA and SC‐P conjugates. SC‐P conjugate at the weight ratio of 1:2 exhibited the best emulsifying properties (emulsifying activity – 46.7%, emulsion stability – 7 days at 5 ± 1 °C storage) and had better solubility (33.5%) near the iso‐electric pH.     

Functional properties of 8S globulin fractions from 15 mung bean (Vigna radiata (L.) Wilczek) cultivars

The functional properties including solubility, water absorption capacity, oil absorption capacity, foaming properties and emulsifying properties of 8S globulin fractions from 15 mung bean cultivars were investigated in this study. In addition, the effects of pH on solubility, foaming properties and emulsifying properties were studied. The functional properties of the 8S globulin fractions varied significantly among the different mung bean varieties and exhibited better performance in solubility and emulsion stability compared with soya bean 7S protein. A negative correlation was found between water absorption capacity and oil absorption capacity. Remarkable differences in polypeptides constituents were observed in 8S globulin fractions, and the ratio of 11S/8S globulins has a positive effect on water absorption capacity while a negative effect on oil absorption capacity. As a function of pH, the emulsifying activity indexes of the 8S globulin fractions were found to be distinctly dependent on the solubility, while no significant correlation was found between the emulsifying stability and solubility, nor between the foaming properties and solubility. The foaming capacity showed a strong correlation with foam stability.     

Emulsifying and Foaming Properties of Different Protein Fractions Obtained from a Novel Lupin Variety AluProt‐CGNA® (Lupinus luteus)

The use of vegetable proteins as food ingredient is becoming increasingly important due to their high versatility and environmental acceptability. This work describes a chemical characterization and techno‐functional properties (emulsifying and foaming properties) of 3 protein fractions obtained from a protein‐rich novel lupin variety, AluProt‐CGNA^®. This nongenetically modified variety have a great protein content in dehulled seeds (60.6 g protein/100 g, dry matter), which is higher than soybean and other lupin varieties. A simple procedure was utilized to obtain 3 different fractions by using alkali solubilization and isoelectric precipitation. Fractions 1 and 3 were mainly composed of protein and polysaccharides (NNE), whereas fraction 2 was mainly composed by protein (97%, w/w). Fraction 3 presented interesting and potential foaming properties in comparison to the other fractions evaluated in the study. Besides, its solubility, foaming and emulsifying capacity were practically not affected by pH variations. The 3 fractions also presented good emulsion stability, reaching values above a 95%. SDS‐PAGE showed that fractions 1 and 2 contained mainly conglutin α, β, and δ, but in different ratios, whereas fraction 3 contained mainly conglutin γ and albumins. The results of this work will provide better understanding for the utilization of each protein fractions as potential ingredients in food industry.     

Foaming and emulsifying properties of pea albumin fractions and partial characterisation of surface‐active components

Whole albumin of pea seed (Palb) was extracted from pea flour (var Frilene) by solubilisation at pH 4.9 and dialysis against water. Palb was fractionated by differential solubilisation in 60% methanol, yielding a soluble (S60) and an insoluble (IS60) fraction. The composition of the fractions was determined by SDS‐PAGE and RP‐HPLC. Albumins exhibited a wide variability of surface hydrophobicity. Albumin PA2 was present as a major component in Palb and IS60. Low‐MW hydrophobic albumins were concentrated in S60. Foaming and emulsifying properties of the three extracts were determined in model conditions. Functionality of albumins was highest at acid pH, but the fractions differed in their properties. The presence of PA2 albumin resulted in the best foaming and emulsifying properties. This protein was shown to adsorb preferentially at air/water and oil/water interfaces, whereas low‐MW hydrophilic albumins did not. Low‐MW hydrophobic albumins were also adsorbed at interfaces, as shown by the behaviour of the S60 fraction, but they formed more fragile films than did PA2. This was related to the structure of the polypeptide chains. © 2000 Society of Chemical Industry     

Functional properties of protein hydrolysates from pea (Pisum sativum,L) seeds

The aim of this study was to investigate the effects of partial enzymatic hydrolysis on functional properties of two different pea protein isolates obtained from two pea genotypes, Maja and L1. Papain and commercial protease (Streptomyces griseus protease) were used for protein modification. Solubility, emulsifying and foaming properties were estimated at four different pH values (3.0, 5.0, 7.0 and 8.0). Papain increased solubility of L1 pea protein isolate at pH 3.0, 5.0 and 8.0, emulsifying properties and foaming capacity at all pH values. Otherwise, papain increased solubility of Maja pea protein isolate only at pH 8.0. This pea protein isolate modified with both enzymes formed emulsions with improved stability at lower pH (3.0, 5.0). The commercial protease‐prepared pea protein isolates showed generally low solubility and different emulsifying and foaming properties. Proper selection of enzyme, conditions of hydrolysis and genotypes could result in production of pea protein isolates with desirable functional properties.     

Improved emulsion stabilizing properties of whey protein isolate by conjugation with pectins

Functional properties of glyco-protein conjugates of the anionic polysaccharide pectin with whey protein isolate, obtained by dry heat treatment at 60 °C for 14 days, have been investigated in O/W emulsions containing 20% (w/w) soybean oil and 0.4% (w/w) protein both at pH 4.0 and 5.5. Emulsion stabilizing properties of mixtures and conjugates were compared at five protein to pectin weight ratios by determining changes in droplet size distribution and extent of serum separation with time. The results indicated that the dry heat-induced covalent binding of low methoxyl pectin to whey protein, as shown by SDS-PAGE, led to a substantial improvement in the emulsifying behaviour at pH 5.5, which is near the isoelectric pH of the main protein β-lactoglobulin. At pH 4.0, however, a deterioration of the emulsifying properties of whey protein was observed using either mixtures of protein and pectin or conjugates.The observed effects could be explained by protein solubility and electrophoretic mobility measurements. The protein solubility at pH 5.5 was hardly changed using mixtures of protein and low methoxyl pectin or conjugates, whereas at pH 4.0 it was decreased considerably. Electrophoretic mobility measurements at pH 5.5 revealed a much more pronounced negative charge on the emulsion droplets in the case of protein–pectin conjugates, which clearly indicated that conjugated pectin did adsorb at the interface even at pH conditions above the protein's iso-electric point. Hence, the improved emulsifying properties of whey protein isolate at pH 5.5 upon conjugation with low methoxyl pectin may be explained by enhanced electrosteric stabilization.Comparing two different commercial pectin samples, it was clearly shown that the dextrose content during dry heat treatment of protein–pectin mixtures should be as low as possible since protein–sugar conjugates not only resulted in increased brown colour development, but also gave raise to a largely decreased protein solubility which very badly affected the emulsifying properties.     

Effect of medium molecular weight xanthan gum in rheology and stability of oil‐in‐water emulsion stabilized with legume proteins

Xanthan gum is a water‐soluble extracellular polysaccharide that has gained widespread commercial use because of its strong pseudoplasticity and tolerance to high ionic strength, which bring unique rheological properties to solutions. This study compares and evaluates the emulsifying properties of oil‐in‐water (30:70 v/v) emulsions stabilized with lupin and soya protein isolates and medium molecular weight xanthan gum. The protein was obtained by an isoelectric precipitation method and the polysaccharide was produced by Xanthomonas campestris ATCC 1395 in batch culture in a laboratory fermenter (LBG medium) without pH control. The addition of xanthan gum in the emulsion formulation enhances emulsion stability through the phenomenon of thermodynamic incompatibility with the legume protein, resulting in an increase of the adsorbed protein at the interface. The emulsion stability is also enhanced by a network structure built by the polysaccharide in the bulk phase. Copyright © 2005 Society of Chemical Industry     

Improved extraction of disulphide‐rich bioactive proteins from soya hulls: characterisation of a novel aspartic proteinase

Soya hull, an underutilised coproduct of soya processing, was investigated as a source of disulphide‐rich bioactive proteins. A Viscozyme L‐assisted extraction method was developed to improve the yield of extracted proteins. The extracted proteins were identified by MALDI TOF–TOF MS, and the most abundant disulphide‐rich protein among identified proteins was purified and the enzymatic properties were evaluated. The results indicated that the Viscozyme L‐assisted extraction method extracted significantly (P < 0.05) more proteins (39.01%) than did the aqueous method (4.52%). The yield of the purified aspartic proteinase nepenthesin‐1‐like [Glycine max] (GmAPN1K) (the most abundant disulphide‐rich protein) is 570 mg Kg^?1. The specific activity of GmAPN1K was 62.1 U mg^?1 at pH 3.0 and 37 °C. The enzyme was optimally active at pH 3.0 and 55 °C. It was stable within pH range 3.0–10.0 and up to 55 °C, respectively, and was specifically inhibited by pepstatin A.     

Relationship between physicochemical and functional properties of amaranth (Amaranthus hypochondriacus) protein isolates

Protein isolates from six amaranth lines/cultivars (APIs) were evaluated to study their physicochemical (hunter colour, protein content and zeta potential), structural (thermal and conformational) and functional (emulsification, foaming, water and fat absorption) properties. APIs had protein content, whiteness index and gel temperature in range of 79.4–85.4%, 41.17–54.26 and 87.8–91.8 °C, respectively. The Fourier‐transform infrared spectra of APIs revealed α‐helix, β‐sheets and random coil conformations in the secondary structure. APIs with higher relative proportion of β‐sheets had higher Differential Scanning Calorimeter denaturation temperature and gel temperature. Minimum protein solubility (PS) was observed at pH 5.0, indicating isoelectric point (pI) of amaranth proteins. The PS, emulsifying activity index (EAI), emulsifying stability index (ESI), foaming capacity (FC) and foam stability (FS) of APIs at neutral pH were related to their zeta potential (ζ). The emulsifying and foaming properties were also determined at different pHs (between 2.0 and 9.0). The EAI‐pH profile of APIs confirmed close relationship between the emulsifying ability and PS.     

In vitro β‐Carotene Bioaccessibility and Lipid Digestion in Emulsions: Influence of Pectin Type and Degree of Methyl‐Esterification

Citrus pectin (CP) and sugar beet pectin (SBP) were demethoxylated and fully characterized in terms of pectin properties in order to investigate the influence of the pectin degree of methyl‐esterification (DM) and the pectin type on the in vitro β‐carotene bioaccessibility and lipid digestion in emulsions. For the CP based emulsions containing β‐carotene enriched oil, water and pectin, the β‐carotene bioaccessibility, and lipid digestion were higher in the emulsions with pectin with a higher DM (57%; “CP57 emulsion”) compared to the emulsions with pectin with a lower DM (30%; “CP30 emulsion”) showing that the DM plays an important role. In contrast, in SBP‐based emulsions, nor β‐carotene bioaccessibility nor lipid digestion were dependent on pectin DM. Probably here, other pectin properties are more important factors. It was observed that β‐carotene bioaccessibility and lipid digestion were lower in the CP30 emulsion in comparison with the CP57, SBP32, and SBP58 emulsions. However, the β‐carotene bioaccessibility of CP57 emulsion was similar to that of the SBP emulsions, whereas the lipid digestion was not. It seems that pectin type and pectin DM (in case of CP) are determining which components can be incorporated into micelles. Because carotenoids and lipids have different structures and polarities, their incorporation may be different. This knowledge can be used to engineer targeted (digestive) functionalities in food products. If both high β‐carotene bioaccessibility and high lipid digestion are targeted, SBP emulsions are the best options. The CP57 emulsion can be chosen if high β‐carotene bioaccessibility but lower lipid digestion is desired.     

全蛋液pH值对其功能性质的影响

对全蛋液pH值对其蛋白溶解度、起泡性、乳化性、凝胶强度等功能性质的影响进行了研究。结果表明:在pH 6.5～9.0内,随着全蛋液样品pH值升高,全蛋液的蛋白溶解度、乳化稳定性和凝胶强度逐渐提高,而全蛋液乳化活力逐渐下降;在pH 7.0～7.5内,全蛋液具有较好的起泡力和泡沫稳定性,pH值过高或过低时全蛋液起泡性都会下降;在实际应用中可以根据对全蛋液各种功能性质的不同要求选择适当pH值的全蛋液。     

Thermal denaturation and functional properties of egg proteins in the presence of hydrocolloid gums

The aim of this study was to investigate the thermal stability, foaming and emulsifying properties of egg white and egg yolk constituents (egg yolk plasma and egg yolk granule) in the presence of hydrocolloid gums. Differential scanning calorimetry was used to examine the thermal stability of proteins. Heat denaturation of proteins were not influenced from the presence of anionic pectin and i-carrageenan and neutral guar gum. The residual denaturation enthalpy was observed to decrease as a result of protein aggregation. Thermal treatment have been observed to be detrimental to foaming capacity of egg white, while foam stability was improved. The foam stability was enhanced in the presence of pectin which may provide a strong viscoelastic film together with protein. Emulsifying activity and stability and of egg yolk granule and plasma were reduced after heat treatment. The presence of guar gum improved the emulsifying properties, while both pectin and guar gum reduced the rate and extend of creaming of egg yolk protein – stabilized proteins after heat treatment.     

苦杏仁蛋白的功能特性

采用稀盐溶液浸提及等电点盐析相结合的方法提取制备苦杏仁蛋白,研究pH值、NaCl浓度、蛋白质量浓度和温度等因素对苦杏仁蛋白功能特性(溶解性、持水性、吸油性、乳化性及乳化稳定性、起泡性及起泡稳定性)的影响。结果表明：在等电点pI附近时,苦杏仁蛋白的溶解性、持水性、乳化性及乳化稳定性、起泡性最差;在较低NaCl浓度范围内(0～0.8mol/L)提高NaCl浓度可促进蛋白溶解性、乳化性及乳化稳定性、起泡性及起泡稳定性的提高,而较高的NaCl浓度对蛋白功能特性提高具有抑制作用;当蛋白质量浓度达到一定水平时(3～4g/100mL),蛋白功能特性(乳化性及乳化稳定性、起泡性及起泡稳定性)提高趋于平缓;在适宜的温度范围内,提高温度可有效提高苦杏仁蛋白各项功能特性,但当温度继续上升,各项功能特性持续降低。     

Preparation of environment‐friendly pectin from sugar beet pulp and assessment of its emulsifying capacity

This study was designed to prepare environment‐friendly pectin from sugar beet pulp (SBP) using subcritical water combined with ultrasonic treatment. Plackett–Burman design based on nineteen different parameters was applied to study the influence of various factors on the characteristics of sugar beet pulp pectin (SBPP). About 29.1% pectin, 62% degree of methylation (DM) and 36% acetylation (DA), and 42.5‐kDa average molecular weight (AMW) were obtained from SBP when using distilled water with solid/liquid ratio of 1:81 for extraction at 110 °C. The yield of SBPP and galacturonic acid (GalA) was mainly affected by solid/liquid (S/L) ratio, water purity and extraction temperature. The ultrasonic temperature, ultrasonic power and extraction temperature were the main factors effecting on neutral sugar content, DM, DA and AMW. Compared with gum arabic (GA), the highest yield SBPP fraction had better emulsifying activity, but poorer emulsion‐stabilizing ability.     

大豆分离蛋白起泡性和乳化性影响因素的研究

大豆分离蛋白的乳化性和起泡性与蛋白质、NaCl、卡拉胶、蔗糖和山梨酸钾含量、pH值、加热温度等密切相关。蛋白质质量浓度分别为2.0g/100mL和2.5g/100mL时,大豆分离蛋白乳化性和起泡性分别达到最大值;远离pH4.5,大豆分离蛋白起泡性和乳化性增加;加热温度45℃时起泡性最好,而乳化性最差;氯化钠、卡拉胶、山梨酸钾添加量分别为1.00g/100mL、0.20g/100mL、0.08g/100mL时,起泡性和乳化性好;添加蔗糖会使蛋白质的起泡性下降,而蔗糖添加量6.0g/100mL时乳化性好。     

Structural modifications of sugar beet pectin and the relationship of structure to functionality

The emulsifying properties of sugar beet pectin (SBP) were investigated in relation to its molecular structure. SBP has been subjected to an enhancement process, and this material was here compared with conventional non-enhanced SBP. The oil-in-water emulsification properties of both were compared at 1.5% concentration at pH 3.25, using 15% middle-chain triglyceride as the oil phase. Their emulsification behavior after various enzyme treatments decreased in the order: protease > arabinanase/galactanase mixture > polygalacturonase. The enzyme treatment also decreased the molecular weight of SBP. Protease degraded the high molecular weight carbohydrate–protein complex. Arabinanase/galactanase mixture was more effective in decreasing the emulsification performance than polygalacturonase. The results confirm the key role of protein as the anchor for the oil droplets and identify also the contribution of the neutral lateral chains in stabilizing emulsions by forming a hydrated layer. Protein also aggregates, which functions as a linker for the association of the carbohydrate chains consequent to the enhancement process.     

金华火腿副产品蛋白酶解物的功能特性与抗氧化活性研究

目的:研究以金华火腿副产品为原料制备的蛋白酶解物的功能特性与抗氧化活性.方法:分析金华火腿副产品蛋白酶解物在不同pH值条件下的乳化活性、乳化稳定性、起泡力以及泡沫稳定性;通过体外试验考察不同浓度的酶解物的自由基清除能力、还原力以及抑制脂质过氧化能力.结果:在体系pH9.0时,金华火腿副产品蛋白酶解物显示出较好的乳化与起泡性能.酶解物的抗氧化活性与其浓度有一定的相关性,当酶解物质量浓度为7.5 mg/mL时,超氧阴离子的清除效果最理想;当酶解物质量浓度为10 mg/mL时,DPPH自由基清除率为32%,还原力为0.79.与空白对照组相比,不同浓度的蛋白酶解物均能够抑制亚油酸的自氧化,且随着浓度的增加,抑制效果明显.结论:在碱性条件下,金华火腿副产品蛋白酶解物具有较好的功能特性.金华火腿副产品蛋白酶解物具有一定的体外抗氧化活性.