Reduced Fat Food Emulsions: Physicochemical,Sensory, and Biological Aspects

Fat plays multiple important roles in imparting desirable sensory attributes to emulsion-based food products, such as sauces, dressings, soups, beverages, and desserts. However, there is concern that over consumption of fats leads to increased incidences of chronic diseases, such as obesity, coronary heart disease, and diabetes. Consequently, there is a need to develop reduced fat products with desirable sensory profiles that match those of their full-fat counterparts. The successful design of high quality reduced-fat products requires an understanding of the many roles that fat plays in determining the sensory attributes of food emulsions, and of appropriate strategies to replace some or all of these attributes. This paper reviews our current understanding of the influence of fat on the physicochemical and physiological attributes of food emulsions, and highlights some of the main approaches that can be used to create high quality emulsion-based food products with reduced fat contents.     

Rheological properties,stability and sensory evaluation of low-cholesterol mayonnaises prepared using egg yolk granules as emulsifying agent

No important practical applications have been developed for egg yolk granules until now. However, as they have low cholesterol content and maintain good emulsifying properties, granules could be employed as a potential ingredient in the food industry. In this work, granules obtained in the laboratory by a simple procedure were used as emulsifying agent in mayonnaise preparation. The aim was to develop a low-cholesterol mayonnaise with properties similar to those of typical mayonnaise. For this purpose, three low-cholesterol formulations prepared in the laboratory were compared with a mayonnaise prepared using yolk and also with a commercial mayonnaise. The rheological characteristics of mayonnaises were evaluated, as well as their microstructure and sensorial properties. In addition, colour and particle size measurements at different times of storage were carried out to assess stability. According to results, the use of granules allows the preparation of a low-cholesterol mayonnaise which shows similar characteristics to those of a typical mayonnaise.     

Optimization of replacing pork back fat with grape seed oil and rice bran fiber for reduced-fat meat emulsion systems

The effects of reducing pork fat levels from 30% to 20% and partially substituting the pork fat with a mix of grape seed oil (0%, 5%, 10% and 15%) and 2% rice bran fiber were investigated based on chemical composition, cooking characteristics, physicochemical and textural properties, and viscosity of reduced-fat meat batters. For reduced-fat meat batters containing grape seed oil and rice bran fiber the moisture and ash contents, uncooked and cooked pH values, yellowness, cohesiveness, gumminess, chewiness, and sarcoplasmic protein solubility were higher than in the control samples. The reduced-fat samples with increasing grape seed oil concentrations had lower cooking loss, emulsion stability, and apparent viscosity. The incorporation of grape seed oil and rice bran fiber successfully reduced the animal fat content in the final products while improving other characteristics.     

Quality characteristics of reduced-fat frankfurters with pork fat replaced by sunflower seed oils and dietary fiber extracted from makgeolli lees

The effects of reducing pork fat levels from 30% to 20% by partially substituting pork fat with a mix of sunflower seed oil (0, 5, 10, 15, and 20%) and makgeolli lees fiber (2%) were investigated based on physicochemical properties, textural properties, and sensory characteristics of reduced-fat frankfurters. The moisture and ash content, and lightness were higher in reduced-fat frankfurter samples containing sunflower seed oil and makgeolli lees fiber than in the control. The results showed that reduced-fat frankfurter samples with higher sunflower seed oil levels had lower redness and yellowness values, as well as less cooking loss, emulsion stability, hardness, springiness, and apparent viscosity. The results of this study show that incorporating sunflower seed oil and makgeolli lees fiber into the formulation successfully reduced animal fat in frankfurters, while improving quality characteristics.     

Microstructure & rheology of mixed colloidal dispersions: Influence of pH-induced droplet aggregation on starch granule–fat droplet mixtures

The creation of high quality reduced-fat food products is challenging because the removal of fat adversely affects quality attributes, such as appearance, texture, and flavor. This study investigated the impact of pH-induced droplet aggregation on the properties of model food systems consisting of fat droplets and starch granules. Oil-in-water emulsions (2 wt.% oil) containing whey-protein coated lipid droplets aggregated extensively when heated (90 °C, 5 min) at pH values around their isoelectric point (pH 5) but not at lower (pH 3.5) or higher (pH 7) values, which was attributed to changes in electrostatic repulsion. The physicochemical properties of mixed lipid droplet–starch dispersions (2 wt.% oil, 4 wt.% starch) prepared under similar conditions (pH 3.5, 5, and 7; 90 °C for 5 min) were also measured. At pH 5, extensive lipid droplet aggregation was observed in mixed systems, which led to a large increase in their yield stress and apparent viscosity when compared to mixed systems at pH 3.5 and 7. These results show that the rheological properties of mixed fat droplet–starch granule suspensions can be modulated by controlling the electrostatic interactions between the fat droplets so as to change their flocculation state. This study has important implications for fabricating high quality reduced-fat products with desirable sensory attributes.     

Emulsion Stability and Sensory Quality of Beef Frankfurters Produced at Different Fat or Peanut Oil Levels

Frankfurters were produced at 12, 20 and 29% fat levels using beef fat or 60% substitution with peanut oil. Less emulsion stability, lower smokehouse yield and lower sensory juiciness scores were found as final fat content of beef frankfurters was lowered to 12%. Firmness, darkening of external color, and flavor intensity were enhanced in the low fat product. Frankfurters with 60% fat as peanut oil exhibited comparable emulsion stability and sensory quality parameters with no rancid flavor development over a period of 6 weeks at 4°C. They were as acceptable to sensory panels as the 29% beef fat frankfurters. Substitution of 60% of the beef fat with peanut oil resulted in a product with significantly (P < 0.05) less cholesterol content.     

原味沙拉酱的营养评价与关键风味成分分析

为明确原味沙拉酱的营养与风味品质,以原味沙拉酱为研究对象,采用常规的营养成分分析方法和顶空固相微萃取-气相色谱-质谱联用技术,对原味沙拉酱的营养成分和挥发性成分进行分析,并通过感觉阈值,运用相对气味活度法评价挥发性气味成分对总体风味的影响程度。结果显示:原味沙拉酱的水分、灰分、粗蛋白和粗脂肪质量分数分别为17.70%、1.77%、2.67%和76.26%;原味沙拉酱中的必需氨基酸质量分数为34.58%,必需氨基酸含量丰富,必需氨基酸指数为0.77,说明其蛋白为可用的蛋白食物源;原味沙拉酱脂肪酸中含量最高为油酸,不饱和脂肪酸含量较为丰富;其呈鲜味氨基酸主要为谷氨酸和天冬氨酸,占氨基酸总量的63.94%;矿物质元素中Na含量最高,达7.56 mg/g;在原味沙拉酱中共检测出35种挥发性成分,其关键气味物质主要为乙酸、苯乙醛、壬醛、十一醛、肉豆蔻醛、乙酸乙酯和异硫氰酸异丁酯。     

W/O型人造肥牛脂肪的品质改进研究

人造肥牛脂肪是一种白色或乳白色黏稠状W/O型食品乳状液。在前期研究的基础上,通过在油相中添加牛油,应用油脂的同质多晶型特点及牛油的特殊组成来提高肥牛脂肪的稳定性;用一级大豆油与三级大豆油适当调配,来改善肥牛脂肪的颜色。实验结果表明,添加牛油的肥牛脂肪与未加牛油的相比乳化稳定性大大提高,可达到99.5%,而且脂肪的结构、质地、风味也得到改善;三级大豆油添加量为10%时,肥牛脂肪的黄度与亮度与天然牛油最接近。     

Thermally treated soya bean oleosomes: the changes in their stability and associated proteins

Oleosomes are subcellular organelles present naturally in plant seeds for storing lipids. Oleosomes can be used in the preparation of various food products, such as creams, salad dressings, mayonnaise and emulsion. However, food products are always subjected to thermal processing, and therefore, the evaluation of the thermal stability of oleosomes is of great important. The present work aimed to understand the effect of soya bean oleosome-associated proteins (SOAPs) on the thermal stability of soya bean oleosome emulsion (SOE). SOE was thermally treated for 15 min at different temperatures of 65, 75, 85 and 95 °C. The confocal laser scanning microscope (CLSM) and Cryo-SEM of SOE, and as well as fluorescence spectroscopy, circular dichroism of SOAPs were investigated. The stability of SOE was significantly affected by thermal treatments, by modulating the conformational structures of SOAPs, while the composition changed slightly. The results of particle size, zeta potential and CLSM showed that thermal treatments caused aggregations of oleosomes especially at high temperatures (75–95 °C). Thermally treated oleosomes were observed to have a rough surface. Results of this work are useful for understanding the underlying mechanisms of SOAPs in maintaining the thermal stability of SOE.     

Physical and flavour stability of mayonnaise

Mayonnaise a mixture of egg, vinegar, oil and spices is probably one of the oldest and most widely used sauces in the world today. Traditional mayonnaise is an oil-in-water emulsion despite containing 70–80% fat. Careful mixing of the ingredients and the addition of minor constituents help to maintain a closely packed foam of oil droplets. Low-fat mayonnaises need additional ingredients to maintain their stability. Mayonnaise, in common with all high fat foods, is susceptible to spoilage due to auto-oxidation, its stability depending on the type of oil used. Salt, as well as being important in the development of the flavour and stability appears to influence the rate of oxidation of the oil in the emulsion. The characteristic flavour of mayonnaise is derived principally from the addition of mustard, which contains isothiocyanates. These isothiocyanates are stabilized in the aqueous solution by the addition of citric acid. An understanding of the physical and chemical processes involved in the formation of emulsions has allowed the manufacture of mayonnaise, which is much, more stable during long-term storage and the development of products which contain a greater range of novel flavours.     

不同大豆源油脂体对蛋黄酱组成及性质的影响

本研究为了实现大豆油脂体部分替代蛋黄以研发出低脂低胆固醇的蛋黄酱,以高油和低油大豆源油脂体为研究对象,用大豆油脂体部分(油脂体和蛋黄比例为8:2和9:1)及全部替代蛋黄制作蛋黄酱,比较分析了油脂体对蛋黄酱的基本成分、脂肪酸、磷脂及V_E含量的影响,并对蛋黄酱的粘度、质构及流变性进行了分析。结果表明,油脂体蛋黄酱蛋白质含量显著高于普通蛋黄酱(p<0.05),而水分、脂肪、胆固醇、棕榈油酸、磷脂含量均显著低于普通蛋黄酱(p<0.05),油脂体蛋黄酱含有更多的DL-α-生育酚和γ-生育酚;同源油脂体蛋黄酱随油脂体含量增大,水分和蛋白质呈上升趋势,脂肪和胆固醇呈下降趋势;同比例下高油大豆油脂体水分、脂肪和蛋白质含量均显著低于低油大豆油脂体蛋黄酱(p<0.05),而胆固醇含量则显著高于低油大豆油脂体蛋黄酱(p<0.05);油脂体蛋黄酱的粘度、质构和流变性低于普通蛋黄酱;同源油脂体蛋黄酱随油脂体含量增大,粘度和质构性质表现越好,而油脂体含量大小对蛋黄酱流变性影响不大,同比例不同源油脂体蛋黄酱的粘度、质构和流变性无显著差异(p>0.05);流变性分析表明,蛋黄酱为假塑性流体,呈现出弱凝胶性。本研究实现了低脂低胆固醇蛋黄酱的开发,主要采用低油大豆油脂体制作蛋黄酱,油脂体与蛋黄添加比例为9:1。     

Physico-chemical and sensory properties of reduced-fat mortadella prepared with blends of calcium, magnesium and potassium chloride as partial substitutes for sodium chloride

Blends of calcium, magnesium and potassium chloride were used to partially replace sodium chloride (50-75%) in reduced-fat mortadella formulations. The presence of calcium chloride reduced the emulsion stability, cooking yield, elasticity and cohesiveness and increased hardness; however, it yielded the best sensory acceptance when 50% NaCl was replaced by 25% CaCl(2) and 25% KCl. There was no effect of the salt substitutes on mortadella color, appearance and aroma. All salt combinations studied showed stable lipid oxidation during its shelf life. The use of a blend with 1% NaCl, 0.5% KCl and 0.5% MgCl(2) resulted in the best emulsion stability, but the worst scores for flavor. This study suggests that it is possible to reduce the sodium chloride concentration by 50% in reduced-fat mortadella using the studied salt combinations with necessary adjustments to optimize the sensory properties (MgCl(2) 25%; KCl 25%) or emulsion stability (CaCl(2) 25%; KCl 25%).     

EFFECT OF DIFFERENT FATS ON THE QUALITY OF GOAT MEAT PATTIES INCORPORATED WITH FULL-FAT SOY PASTE

Effect of different fats such as goat fat, chicken fat, combination of goat and chicken fat and refined mustard oil (RMO) were evaluated in goat meat patties (GMPs). Patties with 10% RMO contributed significantly ( P <  0.05) better emulsion stability compared with others. There were no significant effects of different fats on physicochemical and textural attributes of patties. Patties with RMO had significantly ( P <  0.05) lower cholesterol content than other groups. GMPs with RMO, chicken fat and chicken and goat fat combination rated higher for all sensory attributes than patties with goat fat, which had significantly ( P <  0.05) higher mouth coating and lower overall acceptability. Flavor and overall acceptability were higher in patties with chicken fat. Histological study showed improper dispersion of goat fat in continuous phase of meat protein matrix (emulsion) compared with others .

PRACTICAL APPLICATIONS

Utilization of hard fats from goat, sheep and buffalo in emulsion-based meat products decreases emulsion stability because of its poor dispersibility, and consequently its cooking yield. Goat fat also contributes to a smeary and greasy mouth-coating problem and reduces the palatability of meat products. Alternatively, chicken fat disperses well in meat emulsion because of its high unsaturation and enhances the flavor of the products. However, the efficient utilization of goat fat is essential to support an economical goat meat production system and for developing meat products. The present study showed successful utilization of goat fat when combined with chicken fat, and the products had similar sensory attributes and acceptability as in meat products with chicken fat and refined mustard oil. This study would also help in better use of excess fat from spent hens in other meat products.     

Isolation of Egg Yolk Granules as Low‐Cholesterol Emulsifying Agent in Mayonnaise

Egg yolk is an essential ingredient for many food products due to its excellent functional properties such as emulsification. However, the consumers’ concern of its cholesterol level has led food industry to seek solutions for its replacement. Utilization of low‐fat egg yolk granules as emulsifier can be an alternative strategy. In this study, granules with low cholesterol content were separated from egg yolk by a simple method under easily scalable centrifugal conditions. The egg yolk granules isolated within 0.17 M NaCl solution achieved a 22.5% yield that was similar to that using higher centrifugation speeds and longer time. The yield of egg yolk granules increased from 25% to 32% when the yolk:water ratio was changed from 1:1 to 1:2. Mayonnaise was prepared to evaluate the emulsifying capacity of the egg yolk granules. It was found that egg yolk granules exhibited similar emulsifying activity as that of whole egg yolk, but a better emulsion stabilizing property that is evidenced by the higher viscosity of mayonnaise prepared with the granules. In addition, the viscosities of mayonnaise prepared by spray dried yolk and granules were slightly higher than the liquid counterpart, showing a further improvement by spray drying on the emulsion stabilizing properties. The mechanical spectra of mayonnaise samples by frequency sweep also suggested that granules favored the formation of stronger 3‐dimensional arrangements of oil droplets and therefore a more stable emulsion. Results suggest that granules isolated within 0.17 M NaCl solution present best emulsifying properties and can be applied as whole yolk replacer in food emulsions.     

Impact of Fat Replacers on the Rheological,Tribological, and Aroma Release Properties of Reduced-Fat Model Emulsion Systems and Processed Cheese

Due to the increasing prevalence of overweight and obesity and their associated health problems, the demand for low-calorie and low-fat foods is growing worldwide, especially in the fast food and convenience sectors. However, fat- or calorie-reduced products are often accompanied by sensory deficiencies. Although fat reduction in foods has been addressed in literature, an ideal fat replacer has not been identified due to the variety of fats, their multifarious functions in foods, and the wide range of food products. The aim of this work was to investigate the influence of selected fat replacers on the properties of reduced-fat model emulsion systems and processed cheese. The use of dietary fibers as fat replacers was of particular interest due to their intrinsic health benefits. In addition, both new and established methods of measurement of sensory attributes were applied and compared to determine correlations of findings between different methods of measurement. Chapter 1 addresses the influence of fat replacers on attributes such as energy density, flowability, and firmness in a real food product, processed cheese. To this end, microparticulated whey protein (MWP), which has been widely used as a fat replacer, and three dietary fibers (corn dextrin (CD), inulin, and polydextrose), were used in reduced-fat processed cheese slices. A reduction in energy density of about 30 to 40% was achieved using a fat replacer compared to standard commercial full-fat processed cheese. Higher CD and inulin concentrations reduced the flowability of the cheese slices upon heating, but only had a minor impact on the firmness of the unheated cheese. The addition of MWP resulted in firmer cheese slices with higher flowability compared to the other fat replacers. However, changes in the MWP concentration had little effect on either property. The results demonstrated that different fat replacers with varying concentrations need to be applied to achieve desired attributes for specific conditions of use, e.g., unheated cheese in sandwiches or heated cheese in cheeseburgers. To evaluate newly developed reduced-fat foods, the impact of fat replacers on sensory properties and aroma release also needs to be investigated, which is addressed in chapters 2 to 4. Due to the complex composition of cheese, systematic investigation of the mode of action of fat replacers is difficult. Therefore, emulsion-based model foods were used to eliminate interfering factors and natural variations of ingredients. The second study (chapter 2) focused on developing and validating appropriate methods to investigate the effects of fat, fat reduction and the use of fat replacers on emulsion systems. Tribology, a comparatively new method in food research, was used to instrumentally analyze selected aspects of food mouthfeel. Reduced-fat salad mayonnaises were prepared as separate samples containing different CD concentrations, and characterized using textural, rheological and tribological analyses together with measures of spreadability and human-sensory analysis. The results showed a very high correlation between tribological measurements and the sensory evaluation of the attribute stickiness. In addition, it was shown that some correlations between instrumental and sensory data were best described by a non-linear correlation (Stevens’ power law), such as the relationship between Texture Analyzer measurements and sensory sensations of firmness. Furthermore, the Kokini oral shear stress correlated very well with the sensory attribute creaminess. Hence, the instrumental analytical methods used showed the potential to predict elements of the sensory analysis and reduce the overall analytical effort. While aroma release plays a key role in consumer acceptance, the influence of fat replacers on this attribute has rarely been studied. The third study (chapter 3) therefore investigated not only techno-functional properties but also the release of typical cheese aromas using a liquid emulsion as a model food. While both MWP and CD exhibited a retarding effect on the release of lipophilic aroma compounds, MWP also reduced the release of hydrophilic aroma compounds. It was also shown that aroma release is not only influenced by a change in viscosity, but also by interactions between aroma compounds and fat replacers. In this context, CD exhibited a similar ability to interact with aroma compounds as fat, which is desirable for the development of low-fat foods. In the final study (chapter 4), the findings and methods developed in chapters 1-3 of this work, supplemented with additional methods, were used to investigate the effect of fat reduction and CD concentration on a model processed cheese spread (PCS). By replacing 50% of fat completely with CD, the fat content of the PCS could be reduced without causing any significant changes in properties compared to the full-fat version, e.g. in firmness, flowability upon heating and aroma release. CD was determined to be a promising fat replacer, mimicking important properties of fat. Additional correlations, such as those between the parameters of Winter's critical gel theory (gel strength and interaction factor) and spreadability and lubrication properties were identified and can help to further reduce the analytical effort. In conclusion, CD has been confirmed as a promising fat replacer in both liquid and semi-solid food emulsion products. Furthermore, this work contributes to closing the research gap in the instrumental measurement of sensory attributes by outlining correlations, for example, between tribological methods and mouthfeel sensations. Thus, the evaluation tools of this work can help to assess the potential applications of new fat replacers without extensive application and sensory testing which significantly shortens the development time for food manufacturers. In addition, the results contribute to a better understanding of the interactions between fat, fat replacers and aroma compounds in food matrices. This facilitates the systematic development of reduced-fat processed cheese and other dairy- and emulsion-based products which meet consumer preferences and accelerate the trend towards healthy eating.     

Effect of processing conditions and composition on sodium caseinate emulsions stability

Many food products such as ice cream, yoghurt, and mayonnaise are some examples of emulsion-based food. The physicochemical properties of emulsions play an important role in food systems as they directly contribute to texture, sensory and nutritional properties of food. One of the main properties is stability which refers to the ability of an emulsion to resist physical changes over time. The aim of the present work was to analyze the effect of processing conditions and composition on sodium caseinate (NaCas) emulsions stability. The main destabilization mechanisms were identified and quantified. The relationship between them and the factors that influence them were also investigated. Emulsions stabilized with NaCas were prepared using an ultrasound liquid processor or a high pressure homogenizer. Stability of emulsions was followed by a Turbiscan (TMA 2000) which allows the optical characterization of any type of dispersion. The physical evolution of this process is followed without disturbing the original system and with good accuracy and reproducibility. To further describe systems, droplet size distribution was analyzed with light scattering equipment. The main mechanism of destabilization in a given formulation depended on different factors such as NaCas concentration, droplet size or processing conditions. The rate of destabilization was markedly lower with addition of sugar or a hydrocolloid to the aqueous phase. Xanthan (XG) and locust bean (LBG) gums produced an increase in viscosity of the continuous phase and structural changes in emulsions such as gelation. Sugars interacted with the protein decreasing particle size and increasing emulsion stability. The stability of caseinate emulsions was strongly affected not only by the oil-to-protein ratio but also by processing conditions and composition of aqueous phase. The structure of the protein and the interactions protein–sugar or the presence of a hydrocolloid played a key role in creaming and flocculation processes of these emulsions.