Yogurt Matrix Research Articles

Optimization of the QuEChERS-UPLC-APCI-MS/MS method for the analysis of vitamins D and K nanoencapsulated in yogurt

A novel approach was developed to simultaneously determine the contents of vitamins D2, D3, K1, and K2 in yogurt fortified with nanoencapsulated vitamins D and K. This method combines QuEChERS extraction with UPLC-APCI-MS/MS analysis. Optimization of the QuEChERS process included fine-tuning the addition of salts using response surface methodology based on the Box–Behnken design. Under the optimized conditions, the developed method exhibited an excellent linearity (R2 > 0.999) across concentrations ranging from 0.5 to 500 µg/L. The limits of detection and quantification (LOD and LOQ) were found to be 0.01–0.04 µg/L and 0.04–0.11 µg/L, respectively, with precision, accuracy, and recovery rates exceeding 94.88 %, and accompanied by acceptable relative standard deviations. Comparative analysis with traditional methodologies revealed the significant advantages of the proposed approach. Previous techniques such as liquid–liquid extraction combined with saponification are time-consuming and require high sample quantities. In addition, dispersive liquid–liquid microextraction requires a long analysis time and exhibits a poor sensitivity, particularly in terms of its LOD and LOQ values. In contrast, our method offers a straightforward, efficient, and reliable sample preparation technique suitable for detecting vitamins D2, D3, K1, and K2 in a yogurt matrix. This study not only demonstrates the feasibility of applying the QuEChERS method for stable vitamin quantification in yogurt, but it also represents an innovative contribution to enhancing the detection sensitivity and efficiency in food analysis. By emphasizing these methodological advancements and comparative benefits, this research underscores the significance of adopting advanced analytical approaches in food science.

Lactoferrin-chia seed mucilage complex coacervates for intestinal delivery of quercetin and fortification of set yogurt

This study aimed to develop complex coacervates utilizing lactoferrin (LF) and chia seed mucilage (CSM) for promoting intestinal delivery of quercetin (Q) and fortification of set yogurt. Three cross-linkers, including calcium chloride (CC), transglutaminase (TG), and polyphenolic complex (HP), were used to further reinforce the coacervate network. Cross-linked coacervates had higher values of coacervate yield, encapsulation efficiency, and loading capacity. They efficiently preserved Q under gastric condition (⁓87%–99%), with CSM-TG-Q-LF being most effective for intestinal delivery of Q. Moreover, digested pellets of the cross-linked coacervates displayed better antioxidant activity than the uncross-linked coacervates with CSM-TG-Q-LF pellets showing maximum bioactivity. The Q-loaded coacervates demonstrated superior assembly in the yogurt matrix compared to the unencapsulated Q. Moreover, the coacervate systems, especially CSM-TG-Q-LF significantly improved the textural properties of yogurt and the stability of Q in it. Therefore, CSM-TG-LF is a promising carrier to promote intestinal delivery and food application of hydrophobic molecules.

Replacement of milk fat by rapeseed oil stabilised emulsion in commercial yogurt

The incorporation of lipid droplets and further characterization of matrices within dairy products may be possible using such adjacent particles as protein complexes/lipids. Among the range of varied emulsions and their functionalities, great attention has recently focused on the fabrication of high internal phase types. Feasibly, stable alternatives structured with health-beneficial lipids like those derived from plants could replace saturated fatty acids. As a fat replacement strategy, the fate of incorporated HIPE would require some adjustments either with storage stability and/or structural feat for the food matrix. Therefore, the replacement of milk fat by rapeseed oil stabilised emulsion in commercial yogurt was investigated. This involved 25%, 50% and 75% rapeseed oil respectively assigned as low (LIPE), medium (MIPE), and high internal phase emulsion (HIPE). Specifically, emulsions were examined by droplet size, encapsulation, pH, zeta potential, phase separation, and rheology. The fat free yogurt supplemented by HIPE were examined by droplet size, zeta potential, pH, color, sensory, texture and microbiological aspects against positive (regular milk fat) and negative (fat free) yogurt controls. Results showed increasing rapeseed oil contents would form smaller droplet-like emulsions. Within the yogurt matrix however, incorporating HIPE would seemingly reduce oil droplet size without much compromise to bacterial viability, sensory, or texture. Overall, this simple method of lipid alternation shows promise in dairy products.

Bioprotection Potential of Lacticaseibacillus rhamnosus LRH01 and Lactiplantibacillus plantarum LP01 against Spoilage-Associated Penicillium Strains in Yoghurt

Penicillium spp. are considered a major spoilage fungus in dairy products. Due to the growing concerns over food safety issues and the demand for “clean label” food products from consumers, the use of lactic acid bacteria (LAB) as a bioprotective tool to control fungal spoilage of dairy products appears to be a promising alternative. Here, the antifungal activities of ten LAB cultures against five dairy-spoilage-associated Penicillium strains were studied in a model system, and the most potent bioprotective cultures were further tested in yoghurt. Lacticaseibacillus rhamnosus (L. rhamnosus) LRH01 and Lactiplantibacillus plantarum (L. plantarum) LP01 exhibited potent antifungal efficacy at low concentrations. The inhibitory effects of cell-containing fermentates (C-fermentates), cell-free fermentates (CF-fermentates), and volatiles produced by the two cultures were tested in a yoghurt serum medium. The C-fermentates showed antifungal effects, while the removal of cells from C-fermentates led to decreased antifungal activities. Volatiles alone displayed some antifungal efficiency, but less than the fermentates. In a yoghurt matrix, the specific effect of manganese depletion by the bioprotective cultures on mold growth was investigated. Here, the LAB cultures could completely suppress the growth of molds, while addition of manganese partially or fully restored the mold growth, demonstrating that manganese depletion played a key role in the antifungal activity of the tested LAB cultures in the yoghurt matrix. Both L. plantarum LP01 and L. rhamnosus LRH01 showed efficient antifungal activities in the yoghurt serum, while L. rhamnosus LRH01 exhibited the most potent inhibitory effects on Penicillium strains when added during the processing of the yoghurt with subsequent storage at 7 °C for 22 days. Our findings suggested that L. rhamnosus LRH01 could be a promising bioprotective culture for yoghurt biopreservation.

The impact of dairy matrix structure on postprandial lipid responses.

This review presents evidence related to the postprandial responses after consumption of dairy products focusing on the effect of the dairy matrix and lipid response, which was also presented as part of a speech at the Nutrition Society Winter Conference, January 2023. The key findings are that the dairy product(s) that differentiate from others in the postprandial TAG response are products with a semi-solid structure. There were no differences in lipid responses between cheese and butter. The main factors viscosity, fat globule size and milk fat globule membrane do not seem to explain the effect of the dairy matrix in the acute postprandial response. In summary, it is very difficult to investigate the effects of the dairy matrix per see and with the few studies conducted to date, no clear cause and effect can be established. Future research should focus on the semi-solid dairy matrix, and studies investigating specifically the yoghurt matrix are warranted.

Listeria spp. transfers further from boots and wheels across flooring surfaces, compared with Salmonella, in the dairy context

Listeria spp. and Salmonella are important foodborne pathogens to control; their likely dissemination on floor material in dairy processing plants via contaminated vectors, like manufacturing boots and trolley wheels, and in two matrix types (reconstituted skim milk and yoghurt) was therefore evaluated. The types of microorganisms present, matrices, and vectors all statistically significantly impacted the relationship between steps/wheel rotations and the resulting concentration of bacteria transferred. Trolley wheels were shown to transfer both pathogens over a greater distance than boots alone, based on a linear model; however, taking into account the median stride of an individual, operators wearing contaminated processing boots were estimated to disseminate Listeria further than Salmonella, particularly in a yoghurt matrix (550 m2). The dissemination of Listeria and Salmonella by movable vectors may account for the apparent re-occurrence of the same strains within food manufacturing environments that appear to be too distant from known harbourage niches.

In Vitro Bioaccessibility and Antioxidant Activity of Phenolic Compounds in Coffee-Fortified Yogurt.

Yogurt is considered one of the most popular and healthy dairy products, and has been exploited as a delivery matrix for phenolic compounds. In this study, coffee powder was added to yogurt as a functional ingredient to produce coffee-fortified yogurt. Total phenolic compounds, antioxidant activity and individual hydroxycinnamic acids have been identified and quantified through mass spectrometry. The results from coffee-fortified yogurt were compared with fermented coffee and plain yogurt. Coffee-fortified yogurt had higher total phenolic content and antioxidant activity compared to plain yogurt. However, the total phenolic compounds found in coffee-fortified yogurt represented only 38.9% of the original content in coffee. Caffeoylquinic acids were the most abundant phenolic compounds in coffee. Fermented coffee and coffee-fortified yogurt displayed lower amounts of individual phenolic compounds with respect to coffee (69.8% and 52.4% of recovery, respectively). A protective effect of the yogurt matrix on total and individual coffee phenolic compounds has been observed after in vitro digestion, resulting in a higher bioaccessibility in comparison with digested fermented coffee. Moreover, coffee-fortified yogurt showed the highest antioxidant values after digestion. These findings clearly demonstrate that coffee-fortified yogurt can be considered a significant source of bioaccessible hydroxycinnamic acids, besides its health benefits as a fermented dairy product.

Evaluation of Guava Pulp Microencapsulated in Mucilage of Aloe Vera and Opuntia ficus-indica as a Natural Dye for Yogurt: Functional Characterization and Color Stability.

The substitution of artificial colorants for pigments extracted from fruits is a highly desirable strategy in the food industry for the manufacture of natural, functional, and safe products. In this work, a 100% natural spray-dried (SD) microencapsulated colorant of pink guava pulp, using aloe vera (AV) or Opuntia ficus-indica (OFI) mucilage as functional encapsulating material, was prepared and evaluated as an additive into a yogurt (Y) matrix. The characterization of yogurt samples supplemented with OFI (Y-SD-OFI) and AV (Y-SD-AV) mucilage-covered guava pulp microcapsules was carried out through carotenoid quantification using UV–vis and HPLC–MS techniques, dietary fiber content, antioxidant capacity, colorimetry, and textural analysis, as well as by an evaluation of color stability after 25 days of storage at 4 °C in the dark. These physicochemical characteristics and color stability on the Y-SD-OFI and Y-SD-AV samples were compared with those of a commercial yogurt (control sample, Y-C) containing sunset yellow FCF synthetic colorant (E110). Y-SD-OFI and Y-SD-AV samples exhibited a high content of lycopene, dietary fiber, and antioxidant activity, which were absent in the control sample. Microencapsulated lycopene imparted a highly stable color to yogurt, contrary to the effect provided by the E110 dye in the control sample. The texture profile analysis revealed an increase in firmness, consistency, and cohesion in the Y-SD-OFI sample, contrary to the Y-SD-AV and Y-C samples, which was attributed to the variation in fiber concentration in the microcapsules. The incorporation of OFI and AV mucilage microparticles containing pink guava pulp into yogurt demonstrated its potential application as a functional natural colorant for dairy products.

Consumption of probiotic yogurt and vitamin D-fortified yogurt increases fasting level of GLP-1 in obese adults undergoing low-calorie diet: A double-blind randomized controlled trial.

Energy restriction and manipulation of macronutrient composition of the diet are the main approaches that are used by people who aim to lose weight. When such strategies are employed, appetite and endocrine regulators of satiety, such as gut peptides, all are deeply affected. The gut microbiota–brain axis controls energy homeostasis in humans by affecting central satiety and gut peptides. The purpose of this study was to evaluate if the synergistic effect of probiotics and vitamin D in yogurt matrix can modulate this effect. In the double‐blind, randomized, placebo‐controlled trial, 140 obese adults were randomly allocated into four groups: 1) regular yogurt plus low‐calorie diet; 2) PY plus low‐calorie diet; 3) vitamin D‐fortified yogurt plus low‐calorie diet, and 4) probiotic and vitamin D co‐fortified yogurt plus low‐calorie diet. All groups were encouraged to increase their physical activity. Glucagon‐like peptide‐1 (GLP‐1), peptide Tyrosin‐Tysrosin (PYY), ghrelin, anthropometric variables, insulin, fasting blood sugar (FBS), insulin resistance/sensitivity, 1,25(OH)2 D3, dietary intake, and physical activity were measured before and after 10 weeks. The difference between groups for GLP‐1 after 10 weeks was significant after adjusting for baseline GLP‐1 and protein intake as confounders. PY showed the largest effect size (ES) on GLP‐1 (p = 14.2) and FBS (p = 14) compared with others. Pairwise comparison of yogurts effect sizes on GLP‐1 showed a significant difference in group 1 vs. group 2 (p = .001), group 1 vs. group 3 (p = .003), and group 1 vs. group 4 (p = .048). Vitamin D‐fortified yogurt had the largest effect size on the serum level of vitamin D and it showed a significant difference with RY (p = .018) and PY (p = .002). Consumption of vitamin D‐fortified yogurt and PY could be regarded as a promising approach during calorie restriction.

Microencapsulation of hibiscus bioactives and its application in yogurt

The aim of this study was to evaluate the application of microparticles of anthocyanins from Hibiscus sabdariffa L. extract, obtained by ionic gelation, to commercial natural yogurt. Two ionic gelation techniques were used as follows: atomization (Spray Dryer B-290) and dripping (Encapsulator B-390). Microparticles produced were evaluated for size, morphology, color, and encapsulation efficiency (total phenolic compounds, anthocyanins, and antioxidant capacity). Hibiscus extract (1.5%–4.5%) and 20% of hibiscus microparticles, obtained by atomization or dripping, were applied to whole sweetened natural yogurt and fat-free natural yogurt. Samples were evaluated for sensory acceptance and color changes under refrigerated conditions after the application of different levels of hibiscus extract (1.5%–4.5%). The atomization technique generated smaller particles with a greater encapsulation efficiency of bioactive compounds. Application of free hibiscus extract (4.5%) and hibiscus microparticles (20%) in yogurt matrix proved to be technically feasible, providing color and functional appeal to the product, with good sensory preference. Novelty Impact Statement The double emulsion followed by ionic gelation has allowed good retention of hibiscus anthocyanins. The atomization technique generated smaller particles with a greater encapsulation efficiency of bioactive compounds. Hibiscus extract combined with microencapsulated hibiscus promoted color and functional appeal to yogurt, with good sensory preference.

Effect of In Vitro Gastrointestinal Digestion on Amino Acids, Polyphenols and Antioxidant Capacity of Tamarillo Yoghurts.

Laird’s Large tamarillo powder is high in protein (10%) essential amino acids (EAAs), gamma-aminobutyric acid (GABA) and polyphenols (0.6% phenolics plus anthocyanins) and fibre 25%. This study aimed to investigate, using a standardized static in vitro digestion model, the stability of amino acids and antioxidant capacity of polyphenols in yoghurt fortified with 5, 10 and 15% tamarillo powder either before (PRE) or after (POS) fermentation. Compared to plain yoghurt, the fruit polyphenols (rutinosides and glycosides) were retained and substantial increases in FEAAs (free essential amino acids), total phenolic content (TPC) and antioxidant activity were observed particularly at the end of intestinal phase of digestion. Together with SDS-PAGE results, peptides and proteins in tamarillo yoghurts were more easily digested and therefore may be better absorbed in the small intestine compared to the control. TPC and antioxidant activity of fortified yoghurts increased significantly after in vitro digestion. Relatively high bioaccessibilty of chlorogenic acid and kaempferol-3-rutinoside in digested PRE samples was observed. The results suggest that the yoghurt matrix might protect some compounds from degradation, increasing bioaccessibility and in the small intestine allow increased absorption and utilization possible. Fortification would deliver intact polyphenols and fibre to the large intestine and improve gut health. Further research of acceptability, shelf life, and then trials for health effects should be implemented.

Sensory and Biological Potential of Encapsulated Common Bean Protein Hydrolysates Incorporated in a Greek-Style Yogurt Matrix.

The work aimed to develop a gel as a protective barrier of common bean protein hydrolysates to be incorporated into a Greek-style yogurt and evaluate the sensory perception and biological potential. The gel was formed by complex coacervation and induced heat at a pH 3.5 and 3:1 biopolymer ratio (whey protein and gum arabic). The gel presented a 39.33% yield, low syneresis (0.37%), and a gel strength of 100 gf. The rheological properties showed an elastic behavior (G′ > G″). The gel with the most stable characteristics favored the incorporation of 2.3 g of hydrolysates to be added into the Greek-style yogurt. Nutritionally, the Greek-style yogurt with the encapsulated hydrolysates presented 9.96% protein, 2.27% fat, and 1.76% carbohydrate. Syneresis (4.64%), titratable acidity (1.39%), and viscoelastic behavior presented similar characteristics to the Greek-style control yogurt. The bitterness and astringency in yogurt with encapsulated hydrolysates decreased 44% and 52%, respectively, compared to the yogurt control with the unencapsulated hydrolysates. The Greek-style yogurt with the encapsulated hydrolysates showed the ability to inhibit enzymes related to carbohydrate metabolism (α-amylase (92.47%) and dipeptidyl peptidase-4 (75.24%) after simulated gastrointestinal digestion). The use of gels could be an alternative to transporting, delivering, and masking off-flavors of common bean protein hydrolysates in food matrices to decrease glucose absorption for type 2 diabetes patients.

Potential of brewers’ spent grain in yogurt fermentation and evaluation of its impact in rheological behaviour, consistency, microstructural properties and acidity profile during the refrigerated storage

Brewers’ spent grain (BSG) contains high amounts of dietary fiber, which may regulate the food matrix behaviour. The study aimed to evaluate the impact of spent grain on yogurt. Different levels of BSG were substituted in yogurt fermentation and its impacts on microstructural properties including surface chemical properties and confocal microstructures were studied. The quality of the yogurt was evaluated by determining rheological behavior, syneresis, color, acidity and the amount of lactic acid bacteria (LAB) at 1, 7 and 14 days of storage. The addition of BSG shortened the fermentation time, increased the viscosity and shear stress. FTIR analysis showed that BSG intensifies the band region stretching which describes a modification in a certain functional group. Confocal laser scanning microscopy identified a disruption in the cross-link between fat-protein and yogurt matrix due to the addition of BSG. During the storage, BSG was able to maintain the flow behaviour and stability, which was shown as the change in flow behaviour and syneresis. Furthermore, BSG provided the nutrients for the survival of LAB during the storage and maintained the amount of lactic acid in yogurt during the 14 days of refrigerated storage. The substitution 5%–10% of BSG improved the quality of yogurt as the maximum quality such as acidity, rheological behavior and LAB growth. Even though 15%–20% of BSG generated the same level of acidity and LAB, and had the lowest syneresis, it diminished the flow performance of the yogurt.

Genomic Stability and Phenotypic Characteristics of Industrially Produced Lacticaseibacillus rhamnosus GG in a Yogurt Matrix.

Lacticaseibacillus rhamnosus GG is a widely marketed probiotic with well-documented probiotic properties. Previously, deletion of the mucus-adhesive spaCBA-srtC1 genes in dairy isolates was reported. In this study, we examined the genome preservation of industrially produced L. rhamnosus GG (DSM 33156) cofermented in yogurts. In total, DNA of 66 samples, including 60 isolates, was sequenced. Population samples and 59 isolates exhibited an intact genome. One isolate exhibited loss of spaCBA-srtC1. In addition, we examined phenotypes related to the probiotic properties of L. rhamnosus GG either from frozen pellets or cofermented in yogurt. L. rhamnosus GG from frozen pellets induced a response in intestinal barrier function in vitro, in contrast to frozen pellets of the starter culture. Yogurt matrix, containing only the starter culture, induced a response, but cofermentation with L. rhamnosus GG induced a higher response. Conversely, only the starter culture stimulated cytokine secretion in dendritic cells, and it was observed that the addition of L. rhamnosus GG to the starter culture reduced the response. We conclude that the L. rhamnosus GG genome is preserved in yogurt and that common in vitro probiotic effects of L. rhamnosus GG are observed when examined in the yogurt matrix. IMPORTANCELacticaseibacillus rhamnosus GG is a well-documented probiotic strain recognized for its high acid and bile tolerance and properties of adhesion to enterocytes and mucus. The strain exhibits SpaCBA pili, which have been demonstrated to play an important role in adhesion and therefore are relevant for persistence in the gastrointestinal tract. Recently we demonstrated that the genome and phenotypes of L. rhamnosus GG are preserved throughout an industrial production pipeline. However, as gene deletions in L. rhamnosus GG were previously reported for isolates from dairy products, a key question on the genomic stability of L. rhamnosus GG in a yogurt matrix remained. The aim of this study was to analyze genome stability and phenotypic characteristics of L. rhamnosus GG in yogurt. We found that the genome of L. rhamnosus GG is well conserved when the organism is cofermented in yogurt. Some phenotypic characteristics are consistent in all product matrixes, while other characteristics are modulated.

The Administration Matrix Modifies the Beneficial Properties of a Probiotic Mix of Bifidobacterium animalis subsp. lactis BB-12 and Lactobacillus acidophilus LA-5.

Consumption of dairy products is one of the most natural ways to introduce probiotics. However, the beneficial effects of the probiotics might depend on the administration form. The aim of this study was to investigate the beneficial properties of two probiotic strains: Bifidobacterium animalis subsp. lactis (BB-12) and Lactobacillus acidophilus (LA-5) in different administration forms (capsules and yogurt). First, in vitro resistance to gastrointestinal condition, surface properties, and immunomodulation capacities were determined. Then, the anti-inflammatory properties of the probiotic strains administrated on yogurt or capsules were tested in a dinitrobenzene sulfonic acid (DNBS)-induced colitis mouse model. The survival rates of BB-12 and LA-5 strains to gastrointestinal conditions were slightly higher when yogurt was used as carrier. They showed most affinity to hexane (no-polar basic solvent) than ethyl-acetate (polar basic solvent). BB-12 showed the higher binding capacity to HT-29, Caco-2, and mucin. Both probiotic candidates suppress the secretion of IL-8 secretion by HT-29-TNF-α stimulated cells. Finally, administration of BB-12 and LA-5 strains improve colitis in mice. They protect against weight loss, inflammation, and hyperpermeability induced by DNBS. However, these anti-inflammatory effects were limited when mice were treated with the probiotic strain on a yogurt matrix. Overall results indicate that BB-12 and LA-5 positive properties are compromised depending on the matrix. Consequently, the selection of an appropriate matrix is an important criterion to conserve the positive benefits of these probiotic strains.

Low-methoxyl pectin stabilizes low-fat set yoghurt and improves their physicochemical properties, rheology, microstructure and sensory liking

Addition of low-methoxyl pectin (LMP) was observed to reduce whey loss, improve firmness, rheology, quality and overall liking of low-fat set-yoghurt. LMP addition increased soluble solids content and resulted in higher bacterial counts (≥10 log CFU/g), acidity, bioactivity (DPPH• & ABTS+ μM Trolox/g), and lower pH of set yoghurts. A significant (p < 0.05) improvement in firmness and 16% reduction in whey loss was also observed. As per rheology studies, LMP added set yoghurts possessed higher modulus (G′, G″, G*) and complex viscosity. Power law model parameters (A & z) for G* also related to the enhanced strength of yoghurt matrix on addition of LMP. The dense packing of protein gel structure along with filling action of hydrated hydrocolloid might led to moduli changes in yoghurts. Increasing slope of |G*| and dtan δ values close to zero confirmed higher gel strength of yoghurt added with higher concentrations of LMP. Microstructure revealed open porous network of casein in control, while increased cross-linking with casein or filling of cavities was observed upon addition of LMP in yoghurts. Sensory liking scores showed strong correlation with rheological parameters, while PCA confirmed the effect of LMP concentration on major quality attributes.

Evaluation of the synergistic olfactory effects of diacetyl, acetaldehyde, and acetoin in a yogurt matrix using odor threshold, aroma intensity, and electronic nose analyses

Despite intensive analyses of yogurt flavor, the synergistic effects of the key aroma compounds on sensory responses and their optimum concentration ranges remain less well-documented. This study investigated the odor thresholds, optimum concentration ranges, and perceptual actions of diacetyl, acetaldehyde, and acetoin in a yogurt matrix. Our results show that the odor thresholds of diacetyl, acetaldehyde, and acetoin in the yogurt matrix were 5.43, 15.4, and 29.0 mg/L, respectively, which were significantly higher than the corresponding values in water. The optimum diacetyl, acetaldehyde, and acetoin concentration ranges were found to be 6.65 to 9.12, 25.9 to 35.5, and 37.3 to 49.9 mg/L, respectively. In Feller's additive model, the addition of each compound led to a significant reduction in their odor threshold in the yogurt matrix, thus demonstrating the synergistic effects of the compounds. In the σ-τ plot, various concentrations of compounds were associated with various degrees of additive behavior with respect to the aroma intensity of the yogurt matrix, thus demonstrating the synergism among these compounds in increasing the overall aroma intensity. The optimal simultaneous concentration ratio of diacetyl:acetaldehyde:acetoin was determined to be 4.00:16.0:32.0 mg/L. The specific synergistic effects were also confirmed by an electronic nose analysis and aroma profile comparison. In summary, these 3 aroma compounds exhibited synergistic effects in a yogurt matrix, thus providing a theoretical basis for the enhancement of flavors in dairy products.

Bimodal porous silica nanomaterials as sorbents for an efficient and inexpensive determination of aflatoxin M1 in milk and dairy products

An extraction procedure was developed for the determination of aflatoxin M1 in milk and dairy products. A sorbent based on UVM-7 mesoporous silica was used as solid phase for the sample clean-up, and the analyte determination was carried out by HPLC coupled to a fluorescence detector. The material architecture was characterized by transmission electronic microscopy, X-ray diffraction, 29Si NMR and nitrogen adsorption-desorption. After the optimization of extraction parameters, the influence of the matrix has been evaluated, obtaining recoveries in the range 78–105% for whole and skimmed milk and yogurt matrix. The reusability of the material was also proved. The sensitivity of the method was also evaluated, and a LOQ (0.015 μg kg−1) below the European legislation limit was obtained. The procedure was successfully applied for the determination of aflatoxin M1 in real samples. The results were compared with those obtained with a reference method, being the results statistically comparable.

Live and Dead Bacteria Counts of Different Yogurts Before and After Expiration

Abstract Objectives The objective of this study was to investigate differences in live and dead bacteria counts a month before the expiration date and right after the expiration date and observe any differences in bacteria counts between types of yogurt, brands, and stores tested. Methods Two yogurt containers with the same expiration date were collected for each brand at three stores. The yogurts collected were three national brands of Greek yogurts and five regular yogurts. The first container was tested one month prior to expiry. The second container was tested at the expiration date. After being thoroughly mixed, triplicate 50–75 mg of yogurt were sampled from each carton. Yogurt samples were diluted 9-fold with freshly prepared peptone water. A second dilution was prepared by mixing 25 µL of the yogurt peptone mix with 975 µL of freshly prepared sterile PBS. The samples were incubated for 15 min. at 37°C with 1 µL SYBR green and 5 µL propidium iodine and iced for 1 hour in the dark. 200 µL of dyed yogurt were diluted with 800 µL of PBS and analyzed by flow cytometer (BD Accuri™ C6 Cytometer). Each yogurt sample was run in triplicate on slow speed setting. Flow cytometer parameters were set to differentiate live and dead bacteria based on fluorescence as well as yogurt matrix artifacts. The data was analyzed by a least-squares fit model to test for significance among variables. Results Greek yogurts had significantly higher live and dead bacteria counts compared to regular yogurts. The Greek yogurts differed amongst themselves. Brand 3 had significantly lower live counts than brand 2 and 1. Brand 1 had significantly higher counts of dead bacteria compared to the other two. While differences between Greek yogurt are statistically significant, they are most likely not clinically significant. For the regular yogurt live and dead counts there were no significant differences. No significant differences were observed based on the timing of yogurt sampling or the store the yogurt came from. Conclusions Preparing Greek yogurt involves more straining and whey removal and yields a higher yogurt concentration, so it is no surprise that Greek yogurts have higher bacteria counts. This study demonstrates that when considering yogurt for its probiotic qualities, the most relevant factor is the type of yogurt. Yogurt brand, store, or when it is sampled have little effect on the probiotics count. Funding Sources USU.

Stability of Hibiscus Extract Encapsulated by Ionic Gelation Incorporated in Yogurt

Encapsulation techniques can protect active components from degradation during storage while maintaining their functionality. The purpose of this study was to evaluate the use of double emulsion followed by ionic gelation in the encapsulation of the extract of Hibiscus sabdariffa L. anthocyanin (HE) in the application of the microparticles in a yogurt food matrix. The ionic gelation methods used were dripping-extrusion—D (Encapsulator Buchi B-390)—and atomization—A (Spray Dryer Buchi B-290). Double emulsion (HE/rapeseed oil/pectin) and a cross-linked solution (CaCl2) were employed. Yogurt matrix was characterized for total dry matter, total lipids, protein content, total lactic bacteria, pH/acidity, phenolic compounds (Folin-Ciocalteu), total anthocyanins (differential pH), antioxidant activity (DPPH), color (colorimeter), and morphology (optical microscopy) and was subjected to a sensory appearance acceptability test (80 panelists). The samples were stored in the absence of light (5 ± 1 °C) and monitored every 7 days for total polyphenols, total anthocyanins, color, pH/acidity, and syneresis, for a period of at least 30 days. The use of microparticles obtained by double emulsion followed by ionic gelation and incorporated in yogurt matrix presented technical feasibility, providing color and functionality to the product. The yogurt matrix with microparticles obtained by the atomization technique presented high acceptability of appearance. Microparticles obtained by the dripping-extrusion technique showed greater stability of anthocyanins (48%) and color (ΔE = 1.42) during the yogurt matrix shelf life.