Effect of gamma irradiation on physicochemical,structural and rheological properties of plant exudate gums

This study was undertaken to determine the effect of gamma irradiation on physicochemical characteristics of acacia, apricot and karaya gum. The moisture and carbohydrate content varied significantly (p ≤ 0.05) from 8.83–11.12 and 77.98–83.08 g/100 g, respectively, in native gums. Protein, fat and ash content also varied significantly among the gums (1.63–2.25, 0.09–1.10 and 3.67–5.72 g/100 g, respectively). Functional properties like water absorption, emulsifying, swelling and solubility index increased with the increase in irradiation dose (0–5 kGy). Viscosity of the aqueous gum dispersions measured using RVA decreased with irradiation under natural and acidic environments. Absorbance of the functional groups like –OH, –COOH, uronic acid and pyranose units increased upon irradiation in acacia and karaya gum as confirmed by FT-IR analysis. Irradiation had a pronounced effect on the rheology of acacia and apricot gums reducing their viscosity. In case of karaya gum, there was a transaction of gel-like solid behaviour to viscous liquid behaviour upon irradiation.     

果胶在低糖条件下凝胶的初探

以低甲氧基果胶为例,研究了在低糖条件下,果胶浓度、钙试剂种类及使用量、溶液pH、溶液温度及加热时间不同对果胶凝胶的影响。通过单因子实验、正交实验、感官评定等方法得出最佳凝胶组合,目的在于开发低糖食品。     

马铃薯果胶流变特性的研究

以马铃薯果胶(potato pectin extracted by chelating agent,PPCH)为研究对象,研究果胶溶液质量分数、剪切速率、温度、pH、金属离子等因素对马铃薯果胶流变学特性的影响.研究表明,PPCH溶液的黏度随溶液质量分数上升而增加.随着剪切速率的增大,PPCH溶液黏度下降,剪切变稀现象随...     

柚皮果胶理化性质的研究

以柚皮干粉为原料提取果胶,采用正交实验优化柚皮果胶提取工艺,并对其理化性质进行检测。研究表明在提取温度100℃,pH2.0,时间60min,料液比1∶50(g/mL)的条件下柚皮果胶的得率最高,为27.06%,纯度达84.3%,酯化度为73.75%,所得果胶为淡黄色。常温下pH为4.86,属于酸性高酯果胶。柚皮果胶的溶解度随温度升高而增大、随着pH增大,溶解度有下降的趋势;柚皮果胶的热稳定性优于商品果胶,但随着时间增加迅速降低,15min后趋于稳定;柚皮果胶粘度与果胶浓度和蔗糖浓度的正相关,随pH的增大和温度的升高而下降;柚皮果胶理化性质与商品柑橘果胶相似,柚皮果胶的粘度和乳化性能优于商品柑橘果胶。实验结果表明柚皮果胶是一种优质的果胶。      

柿果胶提取工艺优化及理化性质研究

为了开发柿深加工产品,以脱涩柿果为原料,利用Box-Behnken方法设计,通过响应面分析法对柿果胶的酸提醇沉法提取工艺进行优化,并研究提取的柿果胶的理化性质。结果表明,柿果胶最佳提取条件为0.1 mmol/L HCl提取液pH4.00,液料比为23:1 (g/g),提取时间107 min,提取温度92 ℃,在此条件下柿果胶得率为7.31%。对上述条件下柿果胶的理化性质研究发现,柿果胶的亮度为L^* 30.74,彩度为C^* 13.04,色度角为h° 44.07,酯化度为98.88%;高效液相测其分子量为405.3 kDa,且单糖组成是岩藻糖、阿拉伯糖、半乳糖、葡萄糖、木糖、果糖和半乳糖醛酸。可为柿果胶的提取和应用提供重要的理论基础和技术支持。     

甘薯果胶物化特性的研究

以购买的柑橘果胶和苹果果胶作为对照,分别比较了甘薯果胶与这两种果胶颜色、溶解度、黏度、乳化特性等物化特性的差异,并分析了甘薯果胶的糖构成成分。结果表明:甘薯果胶的溶解度、黏度略低于柑橘果胶,高于苹果果胶,并且具有较好的乳化稳定性。同时,甘薯果胶中半乳糖醛酸和葡萄糖的含量较高。     

Improvement of rheological and physicochemical properties of longan honey by non‐thermal magnetic technique

A non‐thermal technology using magnetic field (MF) can improve flowability of honey while maintaining its physicochemical quality. Effects of MF treatment on rheological and physicochemical properties of longan honey exposed to MF for 2 h at 15 °C and 28 °C were investigated and compared with those of non‐MF samples. Increasing MF strength at 28 °C caused a reduction in firmness (P ≤ 0.05), but not in consistency, index of viscosity and cohesiveness. The effects at 15 °C were greater. Newtonian behaviour was observed for all samples. Shear stress and viscosity were significantly reduced with increasing MF strength at 15 °C (P ≤ 0.05), but less at 28 °C. pH was also decreased. Total soluble solids content was increased at both temperatures (P ≤ 0.05). Colour index was not significantly affected by MF, whereas optical density was slightly increased at high MF strengths (P > 0.05). L* values for the MF treated samples were increased (P ≤ 0.05), giving lighter and more pleasant colour to the honey. MF treatment improved overall qualities of honey.     

Morphology,profile and role of chelate-soluble pectin on tomato properties during ripening

To illustrate the role of chelate-soluble pectin (CSP) on fruit properties, neutral sugar composition and morphology of CSP from two tomato cultivars (‘Dongsheng’ and ‘Geruisi’) at two ripening stages (turning and light-red) were investigated by high-performance liquid chromatography (HPLC) and atomic force microscopy (AFM), respectively. Physicochemical properties and firmness of the tomatoes were determined as well. The percentage of wide CSP chains was reduced and the large CSP polymers were found degraded more with lower firmness during ripening. The proportion of galacturonic acid (GalUA) and rhamnose (Rham) increased during tomato ripening in both cultivars. The proportion of xylose (Xyl) and arabinose (Ara) increased in ‘Dongsheng’ tomatoes while decreased in ‘Geruisi’. The results indicate that the morphology and neutral sugar composition of CSP were closely related with firmness of tomatoes.     

Ultrasonic processing influences rheological and optical properties of high-methoxyl pectin dispersions

The effect of high-intensity ultrasound on the rheological and optical properties of high-methoxyl pectin dispersions was studied. Pectin solutions (1.15 wt% pectin, 41.4 wt% sucrose) were treated with high-intensity ultrasound at intensity levels ranging from 0 to 40 W cm⁻² for various times (0–60 min). Samples were adjusted to pH 1.5 to initiate gelation and their dynamic rheological properties (G′, G″) were recorded as a function of time using a rotational rheometer. Ultrasonically pretreated pectin dispersions formed weaker gels with increasing sonication power and time. After 4 h, log G′ of the pectin dispersion that was pretreated at the highest intensity level (40 W cm⁻² and 30 min) was approximately five times lower than log G′ of the untreated dispersion. The change in phase angle [arctan (G′/G″)] with time indicated that the rate of gelation decreased as ultrasonic intensity and application time increased. The turbidity of ultrasonically pretreated pectin dispersions decreased by 50% yielding more transparent gels. Results were attributed to an overall reduction in the average molecular weight of pectin due to cavitational effects. A power law model was fitted to the flow curves of ultrasonically pretreated pectin dispersions to determine both flow behavior index n and consistency coefficient K. With increased sonication power and application time, n increased from 0.6 to 0.97 indicating that the flow behavior changed from viscoelastic to Newtonian.     

脱皮处理对藜麦粉物化特性及结构的影响

为探究脱皮工艺对藜麦粉物化特性及结构的影响,采用差示扫描量热仪、扫描电镜和傅里叶红外光谱等对比脱皮处理前后和传统制粉工艺对藜麦粉的理化性质的变化;结果表明:脱皮处理工艺可以保留藜麦粉中的营养成分,降低其非营养成分含量;藜麦粉热糊稳定性升高;藜麦颗粒脱皮处理后保持完整的粒形;无新特征峰出现;说明脱皮处理对于改善藜麦粉的加工特性效果明显,为藜麦的营养成分、物化特性及结构提供参考。     

甜菜果胶理化性质及加工适用性质研究

本文对甜菜果胶（SBP）的各项理化性质进行了研究,并与商品柑橘果胶（CP）进行对比。研究了果胶中半乳糖醛酸、总糖、蛋白质含量,酯化度,乙酰度等基本理化性质。然后通过傅里叶红外光谱扫描、果胶分子量等指标,研究了甜菜果胶分子结构的基本特性。通过乳液粒径,乳化活性,ζ-电位和显微观察的手段,对其乳化性质进行评价。最后从流体力学性质出发,考察了果胶浓度和温度对其表观黏度的影响。发现甜菜果胶中蛋白质和阿魏酸含量较高,分子量和表观黏度较柑橘果胶更小。且甜菜果胶的乳化性质优于牛血清白蛋白和阿拉伯胶。通过该研究明确了甜菜果胶的加工适应性,同时为进一步研究甜菜果胶的乳化及凝胶特性提供了理论依据。      

海藻酸钠-高甲氧基果胶复合体系凝胶特性的研究--蔗糖、Ca2+、葡萄糖酸-δ-内酯对复合体系凝胶特性的影响

研究了蔗糖、Ca2+、葡萄糖酸-d-内酯对海藻酸钠—高甲氧基果胶复合体系凝胶特性的影响。结果表明:蔗糖、Ca2+对该体系的凝胶特性影响很大,适量蔗糖的添加不仅可增加体系的凝胶强度和持水性,还可增加凝胶的融点;Ca2+的添加可使体系的凝胶类型从热可逆变成热不可逆,且对体系凝胶强度的影响与其对海藻酸钠的影响类似;在海藻酸钠、高甲氧基果胶单独不能形成凝胶的条件下,葡萄糖酸-d-内酯的添加可诱导两种胶的混合物形成凝胶,且该复合物的凝胶强度与葡萄糖酸-d-内酯的浓度、胶体总浓度有关。     

豆腐柴叶果胶的提取与理化性质分析

为探究10月份豆腐柴叶果胶含量与品质,优化果胶提取工艺,提升豆腐柴开发利用效率。首先利用单因素实验比较酸提取法和超声波辅助提取法对果胶提取率的影响,再根据Box-Behnken实验设计原理,对酸法提取果胶工艺进行响应面优化,最后对两种提取工艺得到的果胶进行分离和理化性质比较。结果表明,酸提取法较好,最佳工艺条件为:料液比1∶30,提取温度88℃,提取时间2.2 h,溶液p H1.6,该条件下果胶提取率为10.57%。紫外光谱和红外光谱发现豆腐柴果胶结构与橘皮果胶结构一致。酸法果胶总半乳糖醛酸含量高于超声波辅助提取法,p H、酯化度与橘皮果胶相似,灰分、钙含量高于橘皮果胶,所有指标均达到了行业标准。      

Physicochemical properties and partial structural features of haw pectin

Haw pectin obtained by cold-water extraction displayed higher viscosity than that of commercially available lemon pectin. After hydrolysis using purified polygalacturonase, haw and lemon pectins yielded polygalacturonase-resistant fractions (CP1-1 and LP1-1, respectively) in the high-molecular-weight region. Anion-exchange chromatography of the resistant fractions yielded additional three fractions (Hf1, Hf2, Hf3) for CP1-1 and 2 fractions (Lf1, Lf3) for LP1-1. The acidic fractions Hf3 and Lf3 were similar in structure; however, the sugar content of the neutral fractions Hf1 and Lf1 differed. The structural differences in the fractions Hf1 and Lf1, and the presence or absence of the acidic fraction Hf2 in the pectin molecule might be associated with the difference in viscosity between haw and lemon pectins. Structural analysis revealed that fraction Hf2 was a polysaccharide in which approximately one-third of the main chain was composed of α-1,4-linked GalA, and no α-1,4-linked GalA was present in the remaining two-thirds pectolyase-resistant region. Furthermore, the constituent sugars Gal and Man existed quantitatively in the pectolyase sensitive region of Hf2.     

Chemical,sensory and rheological properties of some commercial German and Egyptian tomato ketchups

The rheological behaviour of eight tomato ketchups measured in the shear rate range from 0.1 to 100 1/s and with oscillatory tests was studied over a wide range of temperatures (0–50 °C) using a Physica UDS 200 rheometer. The results indicated that these tomato ketchups behave as non-Newtonian fluids semi-solid and have a definite yield stress. The relationship between _eff and temperature of all the tomato ketchup brands under investigation was examined. Significantly higher correlation was found between _eff and temperature. The _eff values decrease with an increase in temperature. Oscillatory test data revealed weak gel-like (dispersion structure) behaviour of the ketchup: the magnitudes of G were higher than those of G, and both increased with oscillatory frequency. The effect of temperature on the viscosity can be described by means of an Arrhenius-type equation. The flow activation energy for viscous flow depends on the chemical composition; the flow activation energy increases with the total solids contents. Chemical, physical and sensory tests for tomato ketchups were made.     

Cold,gel-like soy protein emulsions by microfluidization: Emulsion characteristics,rheological and microstructural properties,and gelling mechanism

In this paper we reported the rheological and microstructural properties of a kind of novel cold, gel-like soy protein isolate (SPI) emulsions obtained by means of microfluidization. These gel-like emulsions were formed from untreated and preheated (95 °C, 15 min) SPI at a protein concentration of 6% (w/v), and various oil volume fractions (Φ; 0.2–0.6) and NaCl concentrations (0–500 mM). The rheological properties and microstructure were characterized using steady viscosity and dynamic oscillatory measurements, as well as confocal laser scanning microscopy (CLSM). The characteristics (e.g. droplet size distribution and creaming stability) of the emulsions, formed at lower protein concentrations (e.g. 0.5–4.0%), were also characterized, aiming to reveal the mechanism of the gel-like network formation. The dynamic oscillatory data indicated that both untreated and preheated SPI emulsions exhibited gel-like rheological properties, but the specific apparent viscosity (η) and storage modulus (G′) of the latter ones were much higher at a comparable Φ. Both η and G′ progressively increased upon Φ increasing, indicating enhanced inter-droplet interactions. At a given Φ value (0.3), increasing NaCl concentration progressively increased η and G′ of the preheated SPI emulsions, indicating the importance of electrostatic screening for the gel-like network formation. The CLSM analyses confirmed formation of the gel-like network, mainly composed of aggregated oil droplets, which was closely dependent on the Φ and NaCl concentration. The gel-like network was formed by bridging flocculation of oil droplets, mainly through inter-droplet hydrophobic interactions between the proteins adsorbed at the interface. These results suggested that soy proteins exhibit excellent potential to produce cold, gel-like emulsions, especially through a heat pretreatment followed by microfluidization, which might be of vital importance for the development of soy protein-based formulations, especially as carriers for heat-labile ingredients with health effects.