Interfacial and emulsifying properties of sucrose ester in coconut milk emulsions in comparison with Tween

In this study, sucrose esters were presented as a promising alternative to petrochemically synthesized Tweens for application in coconut milk emulsions. The interfacial and emulsifier properties of sucrose ester (SE), mainly sucrose monostearate, had been investigated in comparison with Tween 60 (TW), an ethoxylate surfactant. The interfacial tension measurement showed that SE had a slightly better ability to lower the interfacial tension at coconut oil–water interface. These surfactants (0.25 wt%) were applied in coconut milk emulsions with 5 wt% fat content. The effects of changes in pH, salt concentration, and temperature on emulsion stability were analyzed from visual appearance, optical micrograph, droplet charges, particle size distributions, and creaming index. Oil droplets in both SE and TW coconut milk emulsions extensively flocculated at pH 4, or around the pI of the coconut proteins. Salt addition induced flocculation in both emulsions. The pH and salt dependence indicated polyelectrolyte nature of proteins, suggesting that the proteins on the surface of oil droplets were not completely displaced by either added nonionic SE or TW. TW coconut milk emulsions appeared to be thermally unstable with some coalesced oil drops after heating and some oil layers separated on top after freeze thawing. The change in temperature had much lesser influence on stability of SE coconut milk emulsions and, especially, it was found that SE emulsions were remarkably stable after the freeze thawing.     

椰子乳饮料的研制

以全脂乳粉、椰浆为原料,探讨了椰子乳饮料的制备工艺条件。通过正交试验研究了椰子乳饮料产品配方及乳化稳定剂的复配方案。结果表明:椰子乳饮料最适配料为全脂乳粉5.0%、椰浆2.0%、白砂糖5.0%、椰子香精0.1%;椰子乳饮料最佳稳定剂为酪朊酸钠0.1%、结冷胶0.03%、蔗糖脂肪酸酯0.02%、单,双甘油脂肪酸酯0.08%。     

Effect of pH and Ionic Strength on the Physicochemical Properties of Coconut Milk Emulsions

ABSTRACT:  Coconut milk (16% to 17% fat, 1.8% to 2% protein) was extracted from coconut ( Cocos nucifera L.) endosperm and diluted in buffer to produce natural oil-in-water emulsions (10 wt% oil). The effect of pH (3 to 7) and NaCl (0 to 200 mM) on the properties and stability, namely, mean particle size, ζ-potential, viscosity, microstructure, and creaming stability, of the natural coconut milk emulsions was investigated. At pH values close to the isoelectric point (IEP) of the coconut proteins (pH 3.5 to 4) and in the absence of NaCl, coconut milk flocculated, but did not coalesce. Flocculation corresponded to low surface charges and was accompanied by an increase in emulsion viscosity. Adding up to 200 mM NaCl to those flocculated emulsions did not change the apparent degree of flocculation. Coconut milk emulsion at pH 6 was negatively charged and not flocculated. Upon addition of salt, the ζ-potential decreased from –16 to –6 mV (at 200 mM NaCl) but this was not sufficient to induce flocculation in coconut milk emulsions. At low pH (< IEP), the positively charged droplets of coconut milk emulsions only flocculated when the NaCl concentration exceeded 50 mM, as the ζ-potential approached zero.     

Influence of sugar surfactant structure on the encapsulation of oil droplets in an amorphous sugar matrix during freeze-drying

The encapsulation of O/W emulsion droplets in a freeze-dried amorphous sugar matrix was investigated, focusing on the impact of the molecular structure of the emulsifying surfactant. O/W emulsions, containing various surfactants, were freeze-dried in the presence of a sugar. Thirty types of surfactants, including eighteen different sugar surfactants and ten types of commercially available sugar ester mixtures, were used. Linoleic acid methyl ester and trehalose were used as the oil phase and sugar. The amounts of oil droplets encapsulated in freeze-dried amorphous sugar matrix were analyzed by Fourier transform Infrared spectroscopy. Sugar surfactants were generally superior to the other classes of surfactants for oil droplet encapsulation during freeze-drying, and there was the optimum alkyl chain length of the sugar surfactant. Sugar esters generally exhibited greater oil encapsulation than sugar ethers. Larger sugar head group appeared to result in better encapsulation in the case of sugar esters, but the opposite tendency was found for sugar ethers. A limited combination of sugar surfactants (15% sucrose mono- and 85% di-stearate) resulted in the maximum oil droplet encapsulation efficiency although these surfactants are individually quite poor in the encapsulation and other tested combinations did not improve the encapsulation efficiency relative to their individual effectiveness.     

复配乳化稳定剂对可可奶的影响

主要研究复配乳化稳定剂对可可奶稳定性的影响,通过正交试验获得复配乳化稳定剂最佳配比为0.01%卡拉胶、0.015%海藻酸钠、0.15%微晶纤维素和0.015%蔗糖酯。     

Immobilization of recombinant thermostable β-galactosidase from Bacillus stearothermophilus for lactose hydrolysis in milk

A recombinant thermostable β-galactosidase from Bacillus stearothermophilus was immobilized onto chitosan using Tris(hydroxymethyl)phosphine (THP) and glutaraldehyde, and a packed bed reactor was utilized to hydrolyze lactose in milk. The thermostability and enzyme activity of THP-immobilized β-galactosidase during storage was superior to that of free and glutaraldehyde-immobilized enzymes. The THP-immobilized β-galactosidase showed greater relative activity in the presence of Ca²⁺ than the free enzyme and was stable during the storage at 4°C for 6 wk, whereas the free enzyme lost 31% of the initial activity under the same storage conditions. More than 80% of lactose hydrolysis in milk was achieved after 2 h of operation in the reactor. Therefore, THP-immobilized recombinant thermostable β-galactosidase from Bacillus stearothermophilus has the potential for application in the production of lactose-hydrolyzed milk.     

糖碳源和氨基酸氮源对苍白杆菌属发酵产生物表面活性剂的影响

该实验为优化苍白杆菌（Ochrobactrum sp.）产生物表面活性剂的发酵条件,比较了不同糖碳源（蔗糖、乳糖、甘油、木糖、果糖）、氨基酸氮源（谷氨酸、天冬氨酸、赖氨酸、精氨酸和缬氨酸）、碳氮比（C/N）（1、10、20、30、40）对生物表面活性剂发酵的影响。结果表明,最优碳源为蔗糖,发酵5 d达最大乳化活性56.30%;最优氮源为天冬氨酸,发酵4 d达最大乳化活性54.00%;最优C/N为10,发酵4 d达最大乳化活性55.75%。     

Effect of emulsifier type on sensory properties of oil-in-water emulsions

This work investigates the fundamental properties of emulsifiers that may contribute to the fat-associated sensory attributes of emulsions. Model oil-in-water emulsions were prepared with 0, 12, 24, 36 and 48% oil and emulsified with seven different emulsifiers; two proteins; sodium caseinate and whey protein, and five different sucrose esters. Emulsions were rated for perceived ‘fat content’, ‘creaminess’ and ‘thickness’ on nine-point category scales. Instrumental measurements of particle size, viscosity, thin film drainage, surface dilational modulus and interfacial tension were made. The sensory results indicate significant main and interactive effects of fat level and emulsifier type. At higher fat levels, emulsions prepared with sodium caseinate and whey protein emulsifiers had higher viscosities and higher sensory scores than those prepared with the sucrose esters. Results indicate that emulsifier type has a significant effect on the sensory properties of oil-in-water emulsions, and relationships between instrumental and sensory measures suggest that this may be due to the interfacial properties of emulsifiers at the oil–water interface. © 1998 SCI.     

Invited review: spray-dried dairy and dairy-like emulsions--compositional considerations

Milk constituents [caseins, whey proteins (WP), lactose, and anhydrous milk fat] are used widely in the manufacture of dehydrated dairy and dairy-like emulsions. When sodium caseinate- (NaCas) and WP-stabilized emulsions with an oil-to-protein ratio ranging from 0.25 to 5 are dehydrated, NaCas is a more effective encapsulant than WP because of its superior emulsifying properties and resistance to heat denaturation. Denaturation degree of WP during drying has been associated with increased powder surface fat and larger droplet size after reconstitution. Encapsulation of NaCas-stabilized emulsions improves in the presence of lactose; powder surface fat was reduced from 30 to <5% when lactose was added at a 1:1 ratio to NaCas in an emulsion containing 30% (wt/wt) oil. This has been related to the ability of lactose to form solid-like (or glassy) capsules during sudden dehydration. Encapsulation of WP-stabilized emulsions is not improved by addition of lactose, although there are conflicting reports in the literature. Storage stability of dehydrated dairy-like emulsions is strongly linked to lactose crystallization as release of encapsulated material occurs during storage at high relative humidities (e.g., 75%). The use of alternative carbohydrates as “matrix-forming” materials (such as maltodextrins or gum arabic) improves storage stability but compromises the emulsion droplet size after reconstitution. The composition of the powder surface has been recognized as a key parameter in dehydrated emulsion quality. It is the chemical composition of the powder surface that dictates the behavior of the bulk in terms of wettability, flowability, and stability. Analyses, using electron spectroscopy for chemical analysis of the surface of industrial milk powders and dehydrated emulsions that mimicked the composition of milk, showed that powder surface is covered mainly by fat, even when the fat content is very low (18 and 99% surface fat coverage for skim milk and whole milk powders, respectively). The functional properties of milk constituents during emulsion dehydration are far from being thoroughly understood; future research needs include a) the encapsulation properties of pure micellar casein; b) a deeper understanding of colloidal phenomena (such as changes in the oil-water and air-oil interfaces) that occur before, during, and after dehydration, which ultimately define emulsion stability after drying; and c) reconciliation of the current different views on powder surface composition.     

Microencapsulating Properties of Trehalose and of its Blends with Sucrose and Lactose

A low melting fraction of milk fat (LMF), with a dropping point (MDP) of 16.7 °C, was encapsulated by freeze‐drying emulsions formulated with trehalose or its blends with 30 wt% lactose or sucrose as hydrophilic phase, and with a mixed of 50 wt% of the palmitic sucrose esters (SE) β‐170 and β‐1670 as emulsifiers. Trehalose or trehalose/sucrose matrices were very efficient to encapsulate LMF (retention values were 82.8%± 3.2% and 90.5%± 3.7%, dry basis, respectively), whereas trehalose/lactose showed a significant decline in initial retention (42.5%± 2.5%, dry basis). The role of emulsion stability, water content, physical state of the matrix, and particle size distribution on LMF loss was investigated by following retention of LMF with time for the powders stored at water activities (a_w) of 0.11, 0.33, 0.44, 0.54, and 0.76. Trehalose emulsion was the most stable. However, encapsulation efficiency was higher for the trehalose/sucrose blend. Despite the high initial degree of crystallization, retention with time for the trehalose matrix was very high at all a_w. The trehalose/lactose blend had a low efficiency to encapsulate LMF, especially at a_w of 0.54 and 0.76. Retention was determined by the counteracting effects of all these factors and was more closely related to structural changes of the encapsulating matrix than to the physical state (amorphous or crystalline) of it.     

蔗糖脂肪酸酯在乳饮料的应用

<正> 蔗糖酯是以从天然的砂糖及植物油脂中提取的脂肪酸作为原料,是具有高安全性的食用乳化剂。三菱化学食品有限公司开发的RYOTO蔗糖酯的纯度,达到95%以上。基本上,蔗糖分子有8个羟基,故能结合到的脂肪酸数目为1～8个。同一个脂肪酸结合的蔗糖单酯,具有高度的亲水性,而在抑菌力、乳化力、分散力、可溶化力、渗透性和面粉制品的改良等各方面,均能发挥优良的效果。至于与多个脂肪酸结合的蔗糖酯,其亲油性高,在乳化力和改善油脂方面效果甚佳。     

国内市售婴幼儿配方乳粉中葡萄糖、果糖、乳糖 及蔗糖含量的检测与分析

目的分析目前市场上售卖的主要品牌婴幼儿配方乳粉中葡萄糖、果糖、乳糖及蔗糖含量,掌握婴幼儿配方乳粉中葡萄糖、果糖、乳糖及蔗糖的质量状况,调查研究乳基婴儿配方食品是否违规添加果糖情况,指导消费者理性消费。方法本文对婴幼儿配方乳粉进行市场随机采样,建立离子色谱-脉冲安培法测定婴幼儿配方乳粉中葡萄糖、果糖、乳糖及蔗糖方法。经处理后的四种物质以高效阴离子交换柱为分析柱,氢氧化钠为淋洗液,梯度洗脱,脉冲安培检测器(PAD)检测,以保留时间定性,外标法定量。对检测数据进行分析。结果目前国内市场销售23品牌中69批次婴幼儿配方乳粉产品质量总体情况良好。结论婴儿配方乳粉中未发现违规添加果糖。     

RYOTO蔗糖酯在油脂产品中的应用

<正> RYOTO蔗糖酯是由蔗糖和天然植物脂肪酸通过酯化合成的具有安全性的非离子表面活性剂。RYOTO蔗糖酯是在蔗糖的羟基上由脂肪酸进行酯化结合的产品:1个蔗糖的分子,总共有8个羟基。理论上,其结合范围可以从1个蔗糖分子与1个脂肪酸结合的单酯产品到1个蔗糖分     

Effect of thermal treatments on the properties of coconut milk emulsions prepared with surface-active stabilizers

Previously we have demonstrated improved stability of coconut milk emulsions homogenized with various surface-active stabilizers, i.e., 1 wt% sodium caseinate, whey protein isolate (WPI), sodium dodecyl sulfate (SDS), or polyoxyethylene sorbitan monolaurate (Tween 20) [Tangsuphoom, N., & Coupland, J. N. (2008). Effect of surface-active stabilizers on the microstructure and stability of coconut milk emulsions. Food Hydrocolloids, 22(7), 1233–1242]. This study examines the changes in bulk and microstructural properties of those emulsions following thermal treatments normally used to preserve coconut milk products (i.e., −20 °C, −10 °C, 5 °C, 70 °C, 90 °C, and 120 °C). Calorimetric methods were used to determine the destabilization of emulsions and the denaturation of coconut and surface-active proteins. Homogenized coconut milk prepared without additives was destabilized by freeze–thaw, (−20 °C and −10 °C) but not by chilling (5 °C). Samples homogenized with proteins were not affected by low temperature treatments while those prepared with surfactants were stable to chilling but partially or fully coalesced following freeze–thaw. Homogenized coconut milk prepared without additives coalesced and flocculated after being heated at 90 °C or 120 °C for 1 h in due to the denaturation and subsequent aggregation of coconut proteins. Samples emulsified with caseinate were not affected by heat treatments while those prepared with WPI showed extensive coalescence and phase separation after being treated at 90 °C or 120 °C. Samples prepared with SDS were stable to heating but those prepared with Tween 20 completely destabilized by heating at 120 °C.     

Biosurfactant-producing bacterium, Pseudomonas aeruginosa MA01 isolated from spoiled apples: physicochemical and structural characteristics of isolated biosurfactant

An extensive investigation was conducted to isolate indigenous bacterial strains with outstanding performance for biosurfactant production from different types of spoiled fruits, food-related products and food processing industries. An isolate was selected from 800 by the highest biosurfactant yield in soybean oil medium and it was identified by 16S rRNA and the two most relevant hypervariable regions of this gene; V3 and V6 as Pseudomonas aeruginosa MA01. The isolate was able to produce 12 g/l of a glycolipid-type biosurfactant and generally less efficient to emulsify vegetable oils compared to hydrocarbons and could emulsify corn and coconut oils more than 50%. However, emulsification index (E(24)) of different hydrocarbons including hexane, toluene, xylene, brake oil, kerosene and hexadecane was between 55.8% and 100%. The surface tension of pure water decreased gradually with increasing biosurfactant concentration to 32.5 mNm(-1) with critical micelle concentration (CMC) value of 10.1mg/l. Among all carbon substrates examined, vegetable oils were the most effective on biosurfactant production. Two glycolipid fractions were purified from the biosurfactant crude extracts, and FTIR and ES-MS were used to determine the structure of these compounds. The analysis indicated the presence of three major monorhamnolipid species: R(1)C(10)C(10), R(1)C(10)C(12:1), and R(1)C(10)C(12); as well as another three major dirhamnolipid species: R(2)C(10)C(10), R(2)C(10)C(12:1), and R(2)C(10)C(12). The strain sweep experiment for measuring the linear viscoelastic of biosurfactant showed that typical behavior characteristics of a weak viscoelastic gel, with storage modulus greater than loss modulus at all frequencies examined, both showing some frequency dependence.     

SPME-GC-MS结合组学技术分析发酵椰奶特征风味与风味物质相关性

为了分析发酵椰奶特征风味与风味物质相关性,利用固相微萃取—气相色谱—质谱联用技术(Solid-Phase Micro Extraction-Gas Chromatography-Mass Spectrometry,SPME-GC-MS)分别对发酵椰奶、原味椰奶和酸牛奶中的风味成分进行测定,同时进行感官评价;并且结合组学技术从感官和风味物质方面分析了发酵椰奶的特征风味。研究结果表明,发酵椰奶感官风味特征在甜味、酸味、椰子味、奶香味、乳脂味以及醇香味感官评分较高,对发酵椰奶的喜好感主要受甜味、酸味、椰子味以及香草味的影响;而相比原味椰奶甜味过高,且伴随有较浓蒸煮味。从发酵椰奶中共检测出23种风味成分,比原味椰奶和酸牛奶分别多5种和2种;相比原味椰奶,发酵椰奶中酸类和酯类物质相对含量分别减少了11.005%和11.670%,而醇类、酮类和醛类物质相对含量分别增加了6.015%,10.295%,1.975%;酸牛奶中酸类物质是其主要风味成分,比发酵椰奶相对含量高31.79%。发酵椰奶中2,3-戊二酮、3-羟基-2-丁酮等风味成分主要贡献了果香味、奶香味和焦糖气味,酯类物质主要贡献了香草味、甜味、椰子味和蒸煮味。     

Production and characterisation of enzymatically produced lauric acid esters of fructose

Lauric acid esters of fructose were produced using immobilised lipase (EC 3.1.1.3; Novozym 435). A molecular sieve was used to shift the reaction towards the synthesis. The mono‐, di‐ and higher esters of lauric acid with fructose were obtained and analysed qualitatively and quantitatively by high‐pressure liquid chromatography (HPLC). At a 5:1 molar ratio of lauric acid to fructose the amounts of monoester, diester and higher esters produced were 37, 53 and 98 mg respectively after 96 h of reaction time. After purification of the products by column chromatography the hydrophile/lipophile balance (HLB) values of fructose monolaurate and fructose dilaurate were found to be 8.95 and 5.3 respectively and their critical micelle concentration (CMC) values were calculated as 7.20 × 10^?5 and 6.40 × 10^?5 M respectively. The CMC values of esters obtained from the conductivity curve and the surface tension curve were significantly (P < 0.05) similar to each other. It was found that when the concentration of surfactant was increased from 0.25 to 0.50% (w/v), stabilisation of the emulsion also increased. Fructose dilaurate showed better stability than the other esters. Separation of the phases reached 70% within 30 h for the emulsion prepared with 0.50% (w/v) of this ester. © 2002 Society of Chemical Industry     

酸奶菌种冷冻干燥保护剂的筛选研究

本研究采用Plackett-Burman设计法，对蔗糖、麦芽糖、乳糖、果糖、葡萄糖、甘油、甘露醇、山梨醇、可溶性淀粉、明胶、抗坏血酸、谷氨酸钠、L-半胱氨酸盐酸盐以及脱脂奶粉等14种材料对德氏乳杆菌保加利亚亚种和唾液链球菌嗜热亚种冷冻干燥的保护效果进行评价。结果表明：对德氏乳杆菌保加利亚哑种在冷冻干燥中有显著保护作用的是蔗糖、甘油、山梨醇以及脱脂奶粉；而唾液链球菌嗜热亚种有效的冷冻干燥保护剂为甘油、谷氨酸钠和脱脂奶粉。     

Emulsifying Effects of Food Macromolecules In Presence of Ethanol

The influence on droplet size of ethanol present during homogenization was investigated for emulsions stabilized by macromolecular emulsifiers: sodium caseinate, whey protein isolate, gelatin and gum arabic. Emulsions produced with polysaccharide gum arabic had increasing droplet size as ethanol concentration increased, in contrast to the protein-stabilized emulsions which had decreasing droplet size (up to 20 % ethanol for gelatin and 30 % ethanol for the milk proteins), followed by increasing droplet size with increasing ethanol concentration. Interfacial tension measurements indicated that the emulsifying property of the macromolecules depended on adsorption at the oil-water/alcohol interface during emulsification.     

Stabilised cocosoy beverage: physicochemical and sensory properties

Beverages formulated from extracts of blanched coconut meat and germinated soybean were compared for their proximate composition to achieve the recommendations for vegetable milks. The stability of cocosoy beverage treated with varying levels (0.2–1.0%, v/v) of a 20% gum acacia solution was determined visually and objectively after 5 days of quiescent refrigerated storage. Cocosoy beverage (50:50, v/v coconut milk to soy milk) had 3.51% protein, 3.53% fat and 5.17% carbohydrate. Similarly, it contained 13.0, 5.2, 14.7, 18.7, 0.5 and 0.3 g kg⁻¹ K, Na, Ca, Mg, Fe and P, respectively. Compared with whole coconut milk and reconstituted whole milk powder, cocosoy beverage had significantly higher total solid contents and viscosity but lower pH and buffer index. A total solids top to bottom (T/B) ratio and protein (T/B ratio) of 0.97 and 1.0, respectively, corresponding to a separation index of 1.0, was obtained in cocosoy beverage stabilised with 1.0% gum acacia. Cocosoy beverage stabilised with 1.0% (v/v) gum acacia was rated significantly higher for all the tested sensory attributes. Cocosoy beverage, similar to whole coconut milk, had high contents of glucose and sucrose, a moderate content of fructose, low content of raffinose and no trace of stachyose. Copyright © 2006 Society of Chemical Industry