Improved creaminess in stirred yoghurt through amylomaltase-treated starch domains

Amylomaltase-treated starch (ATS) has been described as an excellent fat-replacer in set yoghurt. Its functionality as a creaminess enhancer relates to the ability to form domains, which have melting and yielding characteristics in the mouth. This study was intended to understand the functionality of ATS in stirred yoghurt. Sensory evaluation of reduced fat stirred yoghurt samples showed that the creaminess perception of stirred yoghurt with 1.5% fat and 0.5% ATS was comparable with the reference full fat yoghurt containing 3% fat. This showed that ATS was even more effective as a creaminess enhancer in stirred yoghurt than in set yoghurt. This was related to the higher effectiveness of domain formation during storage after cooling in a dispersed system, as a result of stirring of the yoghurt gel, compared with a gelled set-yoghurt system.     

Effect of microfluidization of heat-treated milk on rheology and sensory properties of reduced fat yoghurt

The effects of microfluidization at 150 MPa (MFz) and conventional homogenization at 20/5 MPa (CH) of heat-treated milk on the rheology and sensory properties of non- (0.1%) and low- (1.5%) fat stirred yoghurts were compared. Homogenization conditions clearly affected the sensory properties of reduced-fat yoghurts, but the effect was highly dependent on fat content. MFz of heat-treated milk yielded products with very different sensory profiles from the conventional yoghurts. For non-fat yoghurts, MFz of heat-treated milk enhanced the perception of buttermilk and soft cheese flavours, and natural yoghurt aroma and flavour, but also increased the intensity of undesirable mouthfeel characteristics such as chalkiness, mouth-dryness and astringency. For low-fat yoghurts, MFz significantly improved creaminess and desirable texture characteristics such as smoothness, cohesiveness, thickness, and oral and spoon viscosity. These differences in sensory profiles, especially textural properties, were partially related to rheological properties, particularly flow behaviour. MFz of heat-treated milk resulted in non- and low-fat yoghurts with higher yield stress, more pronounced hysteresis effect and higher viscosity than those of CH yoghurts of similar fat contents. These findings suggest that microfluidization may have applications for production of high-quality yoghurt with reduced-fat content.     

Physical properties of yoghurt manufactured with milk whey and transglutaminase

The effect of milk protein polymerization prior to the yoghurt fermentation process was evaluated by enzymatic reaction with microbial transglutaminase (Streptoverticillium mobaraense). Yoghurt samples were manufactured with 100% milk or by substituting milk with 20 or 30% of liquid milk whey, aimed at determining the use of natural milk whey in dairy products. Transglutaminase was added at a protein ratio of 0.5 U g⁻¹ to all samples and evaluated regarding rheological behavior, syneresis index and texture profile. The addition of enzyme transglutaminase contributed to syneresis prevention and increased the consistency index in yoghurt samples manufactured with milk whey. Yoghurt manufactured from 70% milk plus 20% milk whey, followed by enzymatic treatment, presented similar characteristics to traditionally manufactured yoghurt (C 100), with no alteration in the syneresis of the samples (p > 0.05) and presented texture parameters similar to the control yoghurt (C 100).     

Optimization of analytical procedures for GC–MS determination of phytosterols and phytostanols in enriched milk and yoghurt

The aim of the present study is to contribute to a correct determination of vegetal sterol and stanols found in enriched milks and yogurts, used as functional foods, using GC–MS. The optimization of the method, specially the saponification step, as well as the corresponding analytical validation, is the main goal of this study. Saponification temperatures and times that gave the best results were 80 °C/45 min for milk, and 60 °C/90 min for yoghurt samples. KOH concentration solutions of 2.0 and 2.5 M were selected as the best saponification reagents for milk and yoghurt, respectively. It was also verified that volumes of 1500 μl and 2500 μl KOH were enough to react with 250 μl of milk and 100 μl of yoghurt. Accuracy, repeatability and intermediate precision of the method were calculated at 89.2% and 91.5%, 6.0% and 4.45%, 11.8% and 9.4%, for milk and yoghurt, respectively, while the limit of detection was determinate at 0.1 μg/ml for both matrices.     

Production and evaluation of some physicochemical parameters of peanut milk yoghurt

The peanut milk for yoghurt production was prepared by fortifying peanut milk (∼12 g/100 g total solids) with 4 g/100 g skimmed milk powder. The final product was subjected to physicochemical analysis using cow milk yoghurt (CMY) as a control throughout the study. Peanut milk yoghurt (PMY) had higher protein content, fat, water holding capacity and lower susceptibility to Syneresis than CMY. PMY had lower lactose level (1.73 g/100 ml) compared to CMY (4.93 g/100 ml). Generally both PMY and CMY had high mineral composition and contained high amounts of essential amino acids. PMY also contained a higher proportion of unsaturated fatty acids than saturated fatty acids as compared to CMY. Therefore, in terms of fatty acid composition, PMY could be considered to be more health promoting than CMY. Sensory evaluation revealed that though PMY had better sensory texture scores than CMY, its sensory appearance, flavor and overall acceptability scores were lower than those of CMY.     

Rheological,microstructural and sensory characterization of low-fat and whole milk set yoghurt as influenced by inulin addition

The effect of inulin addition (0–4%) upon texture and microstructure of set yoghurt with different levels of fat (0.2%–3.5%) was investigated. A two-factor experimental design with four treatments was used for data analysis. Skimmed milk with various inulin and cream concentrations was standardized to 4% protein content, homogenized, heated to 92 °C and fermented at 42 °C until a pH of 4.6 was reached. The chemical composition, pH, consistency and microstructure properties of the yoghurts were analysed after 6 days of storage at 5 °C. The statistical analysis showed that inulin and fat significantly affected the rheological and sensory results. Higher yield stress, “firmness” and “creaminess” values were observed in yoghurt produced with higher inulin additions, whereas the pH value was not affected. A significant correlation was found between yield stress and sensory determined firmness (r = 0.91). The microstructure examined by confocal laser scanning microscopy (CLSM) was only slightly affected by the concentrations of inulin in the range studied, possibly due to weak protein interactions between the inulin and the milk protein network.     

The effect of thermosonication of milk on selected physicochemical and microstructural properties of yoghurt gels during fermentation

Yoghurt cultures (0.1, 1.5 and 3.5% fat) were prepared from milk which was preheated to 45 °C and subjected to thermosonication (TS) for 10 min at an ultrasound amplitude of 24 kHz. Compared to conventional yoghurts prepared from preheated (90 °C, 10 min) milk, cultures from TS milk at similar fat contents had higher gelation pH values, greater viscosities and higher water holding capacities (WHC). On average, yoghurts from TS treated milks with 1.5 or 3.5% fat had almost 2 fold greater WHC and 25% higher G’ values than conventionally produced yoghurt. Electron microscopy showed differences in the microstructure, with TS yoghurt having a honeycomb like network and exhibiting a more porous nature. These characteristics are absent in conventional yoghurts. In addition, the average particle size in TS yoghurts was smaller (<1 μm) than in conventional yoghurts.     

Development and validation of analytical methods for ethyl carbamate in various fermented foods

The aim of this work was to develop and validate analytical methods for ethyl carbamate (EC) in various food matrices. Column chromatography was used for the analysis of EC in kimchi, a fermented soybean paste (doenjang), a fermented fish product (jeotgal), yoghurt, bread, and cheese. To remove the fat in the bread and cheese, a Florisil cartridge was selected. The volume of dichloromethane in the chromatography column was optimised to 60 mL for the kimchi, cheese, and fermented soybean paste. For the bread, jeotgal, and yoghurt, the best recovery rate was found by using 100 mL of dichloromethane. For the accurate analysis of EC in the vinegar, 150 mL of dichloromethane and a neutralisation process (pH = 8.0) were required. In the standard curve of EC, satisfactory linearity (R² = 0.998) was shown. The limit of quantification (LOQ) was 10 ng/mL and the recovery rates ranged from 76.9% to 118.1%. Intra- and inter-assay precision ranged from 3.5% to 34.2% and 3.8% to 41.9%, respectively.     

Caffeic acid copigmentation of anthocyanins from Cabernet Sauvignon grape extracts in model systems

Caffeic copigmentation of anthocyanins from Cabernet Sauvignon grape extracts in model system and yoghurt model system was investigated, as well as the influence of copigmentation on the stability of these pigments. In the model system, the dependence of anthocyanin stability on added caffeic acid was evaluated at temperatures (4 ± 1 °C and 29 ± 3 °C) and in the presence or absence of light, at two pH values: 3.0 and 4.0; in the yoghurt model system, the stability of the anthocyanins was evaluated at 4 ± 1 °C in the dark. The half-life and percentage of color retention of the anthocyanins in all treatments was calculated. The spectrophotometric results (Δλ, ΔA) revealed that interaction occurred between the crude extract of anthocyanins and caffeic acid suggesting copigmentation. The addition of caffeic acid (1:1 w/v) significantly increased (p < 0.05) the stability of anthocyanins in both model and yoghurt systems. In the model system the temperature and presence of light significantly influenced the stability of anthocyanins (p < 0.05), where the highest values for half-life were obtained for anthocyanins with caffeic acid at pH 3.0, stored in the dark at a temperature of 4 ± 1 °C (6.930 h). In the yoghurt system the caffeic acid increased the half-life time of anthocyanins to 6673 h.     

Physicochemical properties of lard-based diacylglycerols in blends with lard

The objective of the study was to investigate how blending of triacylglycerols and diacylglycerols affected the melting and crystallisation properties in a solid fat system. Lard-based diacylglycerols (DAGs) were blended with lard in various concentrations (0%, 1%, 5%, 10%, 20%, 50%, 60%, 70%, 80%, 90%, and 100%). The melting and crystallisation properties were investigated by the determination of dropping point (DP), solid fat content (SFC), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). In general, the effects of DAGs were found to be dependent on concentration. The DP was significantly (P < 0.0001) decreased when DAGs were added to the lard from 5–50%, whereas the DP was increased (P < 0.0001) when the blends contained more than 60% DAGs. The DSC thermograms showed that DAGs changed the melting and crystallisation profiles of lard. The crystallisation onset point increased (P < 0.05) with increasing the DAG concentrations (10–100%). The melting peaks and off-set points generally shifted slightly towards higher temperatures as the content of DAGs increased above 50%. DAG content of 5% and 10% resulted in lowering of the off-set point. The lard contained both β and β′ crystals. The β form was more pronounced in the blends with high concentrations of DAGs. Blending of TAGs and DAGs may serve as a solution to achieve specific functional properties in products containing solid fats.     

Interactions between EPS-producing Streptococcus thermophilus strains in mixed yoghurt cultures

Mixed cultures of different EPS-producing Streptococcus thermophilus strains in combination with a Lactobacillus delbrueckii subsp. bulgaricus strain with negligible EPS-production were used for yoghurt production. The yoghurt texture was characterised with respect to sensory, rheological and microstructural properties and the EPS-concentrations were determined. The cultures resulted in yoghurts with highly different texture properties, and positive interactions between certain Streptococcus thermophilus strains were observed. The underlying properties of yoghurt texture are multidimensional, but a number of microstructural characteristics were apparent in the yoghurts with the highest mouth thickness, creaminess and viscosity. A strong protein network, not too dense and with medium size pores containing EPS, seems associated with these properties. The presence of capsular polysaccharides (CPS) also appeared to be beneficial as did a combination of EPS types, which were distributed differently in the protein network (in serum pores, respectively in association with protein). Obviously, a certain concentration of EPS must be present to provide for these effects on yoghurt texture, but other factors than concentration per se seem more important.     

Survival of probiotics encapsulated in chitosan-coated alginate beads in yoghurt from UHT- and conventionally treated milk during storage

Survival of the microencapsulated probiotics, Lactobacillus acidophilus 547, Bifidobacterium bifidum ATCC 1994, and Lactobacillus casei 01, in stirred yoghurt from UHT- and conventionally treated milk during low temperature storage was investigated. The probiotic cells both as free cells and microencapsulated cells (in alginate beads coated with chitosan) were added into 20 g/100 g total solids stirred yoghurt from UHT-treated milk and 16 g/100 g total solids yoghurt from conventionally treated milk after 3.5 h of fermentation. The products were kept at 4 °C for 4 weeks. The survival of encapsulated probiotic bacteria was higher than free cells by approximately 1 log cycle. The number of probiotic bacteria was maintained above the recommended therapeutic minimum (10⁷ cfu g⁻¹) throughout the storage except for B. bifidum. The viabilities of probiotic bacteria in yoghurts from both UHT- and conventionally treated milks were not significantly (P>0.05) different.     

Antioxidant activity of yoghurt peptides: Part 1-in vitro assays and evaluation in ω-3 enriched milk

The aim of the present study was to investigate important factors contributing to the high oxidative stability of fish-oil-enriched yoghurt, with particular emphasis on the possible antioxidative effects of peptides released during yoghurt fermentation. Yoghurt samples were stripped from sugars and lactic acid and subsequently fractionated by ultrafiltration using membranes with cut off sizes of 30 kDa, 10 kDa and 3 kDa. The fractions were tested for antioxidant activity by investigating the inhibition of oxidation in liposome model system, 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activity, iron-chelating activity, and reducing power. The lower molecular weight fractions were found to be more effective antioxidants than higher molecular weight fractions. The lower molecular fractions were further tested as antioxidants in fish-oil-enriched milk. On the basis of peroxide value, volatiles, tocopherol and sensory characteristics, the lower molecular weight fractions 3–10 kDa and <3 kDa showed protection against oxidation of fish oil to the same extent as caseinophosphopeptides. The oxygen content of the yoghurt was also found to be lower than that of milk. Thus our findings suggests that the higher oxidative stability of yoghurt might be due to antioxidant peptides released during the fermentation of milk by lactic acid bacteria and/or by the lower oxygen content of yoghurt, which subsequently reduces the oxidative stress of fish oil incorporated in the yoghurt. The results show that antioxidant peptides may be used as an ingredient in foods enriched with fish oils to increase their oxidative stability.     

Characteristics and composition of Washingtonia filifera (Linden ex André) H. Wendl. seed and seed oil

Characteristics of seeds and oil extracted from Washingtonia filifera seeds are evaluated. The percentage composition of the W. filifera seeds is: ash 1.37%, oil 16.30%, protein content 3.46%, total carbohydrate 77.19% and moisture 3.22%. The major nutrients (mg/100 g of seeds) found in the seeds are: potassium (67.33), magnesium (34.35), calcium (187.85) and phosphorus (23.26). Physicochemical properties of the oil include: iodine value 67.33 g/100 g of oil; saponification value, 191.63 mg KOH/g of oil; refractive index (25 °C), 1.469; unsaponifiable matter, 0.83%; acidity, 0.41%; p-anisidine value, 0.87; peroxide value, 7.60 mEq O₂/kg of oil; carotenoid content 14.8 mg/100 g and the chlorophyll content = 0.13 mg/100 g. W. filifera seed oil shows some absorbance in the UV-B and UV-C ranges with potential use as a broad spectrum UV protectant. The oil contains high levels of oleic acid (40.60%) followed by lauric acid (17.87%), linoleic acid (16.26%), myristic acid (11.43%) and palmitic acid (9.23%). The triacylglycerols (TAGs) with equivalent carbon number ECN 44 (20.47%) are dominant, followed by TAGs ECN 46 (16.71%), TAGs ECN 42 (15.43%) and TAGs ECN 48 (15.41%). The DSC melting curves reveal that: melting point = 2.25 °C and melting enthalpy = 82.34 J/g. γ-Tocotrienol is the major tocol (72%) with the rest being δ-tocotrienol and α-tocotrienol. The results of the present analytical study show that W. filifera seed oil could be used in cosmetic, pharmaceutical and food products.     

Characterization of fish gelatin from surimi processing wastes: Thermal analysis and effect of transglutaminase on gel properties

Fish gelatin extraction from wastes of fish Herring species (Tenualosa ilisha) was carried out by a series of pretreatment with 0.2 M Ca(OH)₂ followed by 0.1 M citric acid and final water extraction at 50 °C for 3 h. The resulting fish gelatin preparation was evaluated for its dynamic viscoelastic properties, gelling and melting temperatures and gel strength. The gelling and melting temperatures of gelatin samples (at 6.67%, w/v) were obtained from differential scanning calorimetry and rheological studies. The melting temperature of extracted fish gelatin (EFG) obtained ranged from 16.2 to 16.7 °C compared to that of commercial fish gelatin gel (CFG), from 23.7 to 25.6 °C and halal bovine gelatin (HBG), from 26.5 to 28.7 °C. On the other hand, gelling temperatures of EFG, CFG and HBG ranged from 5.1 to 5.2 °C, 11.9 to 17.46 °C, and 12.6 to 19.33 °C, respectively. EFG gave gels with a considerably lower G′ values than CFG and HBG. The bloom strength of EFG gels at 6.67% (w/v) was 69.03 g which was much lower than HBG (336.2 g) and CFG (435.9 g). Enzyme transglutaminase was added in the amounts of 0.5, 1.0, 3.0 and 5.0 mg/g gelatin to modify the gel properties of the extracted fish gelatin. The modified EFG gels obtained had higher gel strengths of 101.1 g and 90.56 g with added transglutaminase of 1.0 and 3.0 mg/g, respectively. However with addition of 5.0 mg/g enzyme the gel strength increased only up to 75.06 g. SDS-PAGE of extracted gelatin gel showed protein band intensities for α1-chains and 53 kDa but in gels added with higher concentration of transglutaminase, these protein band intensities seemed to disappear.     

Development of yoghurt from ovine milk with enhanced texture and flavour properties

Six commercial starter cultures, all blends of Streptococcus thermophilus sp. and Lactobacillus bulgaricus sp., were compared for enhanced texture and flavour in yoghurt prepared from ovine milk. The fermentation patterns differed between starters, with YF‐L903 (E) showing the fastest fermentation but slower post‐acidification. YC‐X11 (A) produced the slowest acidification, while YC‐380 (B) resulted in the fastest post‐acidification. Textural and colour properties were affected significantly by the culture used. YF‐L903 (E) enhanced the firmness and luminosity of the yoghurt over storage, increasing mouthfeel and creaminess, as compared to yoghurts prepared with the other starter cultures starters studied.     

Eliciting the Sensory Modalities of Fat Reformulated Yoghurt Ice Cream Using Oligosaccharides

In the present work, fat reduction of Greek strained yoghurt ice cream (YIC) was carried out in three proportional milkfat levels i.e. 30, 50 and 70% using three types of oligosaccharides namely long-chain inulin, oligofructose and maltodextrin 12 DE. Greek strained yoghurt was blended with ice cream mixes in ratios of 1:3 and 1:1. The physico-chemical, textural and thermal characteristics of the YIC mixes and their obtained frozen end products were determined. The sensory modalities (olfactory, gustatory, tactile and oro-tactile) of the YIC were monitored following 2 and 16 weeks of quiescent frozen storage at ?25 °C. Milkfat reduction impaired significantly (p?<?0.05) the perceived creaminess and mouthcoating sensation stimuli, whist it intensified the oral tissue friction associated sense stimuli such as astringency, wateriness and coarseness. Long-chain inulin- and maltodextrin-based samples received the highest scores for creaminess, mouthcoating, gumminess, hardness and iciness. The increase of the yoghurt to ice cream mix ratio escalated the friction/recrystallization-associated sensations e.g. astringency, sourness, coarseness and wateriness. Notwithstanding yoghurt supplementation reinforced the pseudoplasticity and macroviscosity of the ice cream mixes, it suppressed their aeration capacity leading to heavy-bodied ice creams. However, no significant effects of yoghurt supplementation level on the colligative and meltdown rate of the YIC formulations were identified. Partial least squares coupled discriminant analysis (PLS-DA) revealed that fat reformulation of YICs using oligosaccharides results in a substantially diversified sensory profile. Generally, a 50% fat reduction of YICs using long-chain oligosaccharides appears to be a technologically tangible solution.     

Comparison of the effects of high-pressure microfluidization and conventional homogenization of milk on particle size,water retention and texture of non-fat and low-fat yoghurts

The effect of high-pressure homogenization using a Microfluidizer^® on texture, water-holding capacity, and extent of syneresis on stirred yoghurts was compared with that of conventional homogenization. The effect of homogenization condition on particle size was also assessed in milk and in yoghurt. Stirred yoghurts were prepared from recombined milk samples (0 and 1.5% fat) heat-treated (95 °C, 2 min) and then treated by conventional valve homogenization at 25 MPa or microfluidization at 150 MPa. Homogenization conditions influenced the particle size in milk, gel particle size, and textural quality of stirred yoghurts in a manner dependent upon fat content. Milk microfluidized at 150 MPa had smaller particle size than homogenized milk, but resulted in larger particles in yoghurt. Microfluidization of low-fat milk modified the microstructure of yoghurt, giving more interconnectivity in the protein networks with embedded fat globules, but with similar texture profiles and water retention compared with yoghurt made from conventionally homogenized milk.     

Investigating the effect of deforming temperature on the oil-binding capacity of palm oil based shortening

This study investigated the effect of deforming temperature on the oil binding capacity (OBC) of a palm oil-based shortening (melting point 40 °C). The shortening was treated with three different temperature conditions namely, Set A at 25 °C for 8 h, Set B at 40 °C for 8 h and Set C at 70 °C for 2 h. Stability analyzer (LUMiFuge, Germany) that applies centrifugal force with an in-built near infrared (NIR) detector was used to measure the amount of free oil released from the shortenings. Other characteristics such as crystal size, solid fat content (SFC), hardness and aerating ability were also studied. The stability analyzer successfully measured the OBC, with the highest in Set A (99%) followed by Set B (94%) and Set C (89%). The increase of deforming temperature resulted in the increase of crystal size that decreased the OBC, which consequently decreased the SFC, hardness and aerating ability of the shortening.