Natural Yogurt Research Articles

The interaction effect of mixing starter cultures on homemade natural yogurt’s pH and viscosity

Dairy yogurts are common food products consumed by people all over the world. Due to the simple process, many people have made their own natural yogurt at home. The fermentation due to the starter culture causes the textural properties of dairy yogurt. However, the literature is surprisingly scarce on the topic of starter culture interactions in the development of textural properties of dairy yogurt. This study investigated the interaction effect of three common starter cultures, Lactobacillus acidophilus, Lactobacillus bulgaricus and Streptococcus thermophiles, on the viscosity of homemade yogurt. Using Design Expert software, a 10-run mixture model experiment was designed to examine the textural properties developed by single or multiple inoculation of these starter cultures. All yogurt formulations reached the isoelectric point of milk and had pHs in the range 3.97 to 4.32. Yogurt formulations with L. acidophilus and S. thermophilus resulted in viscosities which were similar to commercial yogurt viscosity (1.77 Pa.s), while L. bulgaricus resulted in yogurt with a lower viscosity. Based on the mixture model, L. acidophilus had most influence on the yogurt viscosity, followed by S. thermophilus and L. bulgaricus. In conclusion, L. acidophilus can be used as a single starter culture or combined with other starter cultures to develop high viscosity homemade yogurt. A Combination of S. thermophilus and L. acidphilus can also be used to develop high viscosity yogurts. However, L. bulgaricus should not be inoculated alone or become a dominant ratio in multiple starter culture inoculation as it will decrease the overall homemade yogurt viscosity.

Enhancement of antioxidant activity and physicochemical properties of yogurt enriched with concentrated strawberry pulp obtained by block freeze concentration

Strawberry juice was concentrated using block freeze concentration process. The concentrate was used to produce two yogurts with different concentrations of cryoconcentrated strawberry pulp (15% and 30%). Total lactic acid bacteria count, physicochemical and rheological properties was evaluated during storage (7days) for all yogurts. Also, the beverages produced were compared with two commercial trademarks. It was observed that the total lactic acid bacteria count remained higher than 108CFU·mL−1 during the storage time for all beverages studied. The viscosity of the yogurts decreased when the ratio of strawberry cryoconcentrate was increased. The Power Law model was successfully applied to describe the flow of the yogurts, which had a thixotropic behaviour. The incorporation of the cryoconcentrated strawberry pulp in the yogurt resulted in a product with 3-fold more anthocyanins content and antioxidant activity. The enrichment of natural yogurt with strawberry cryoconcentrated pulp proved to be effective in the production of a beverage with higher nutritional characteristics.

Influence of heat treatment on physicochemical and rheological characteristics of natural yogurts

The aim of this study was to assess the influence of heat treatment on physicochemical and rheological characteristics of natural yogurts, as well as the influence of lyophilization process on natural yogurts after reconstitution. In the first experiment, three yogurt treatments were processed, as follows: Treatment 1, yogurt produced with raw refrigerated milk; Treatment 2, yogurt produced with refrigerated pasteurized milk; and Treatment 3, yogurt produced with UHT (ultra-high temperature) milk, in addition to analyses of fat, protein, moisture, titratable acidity, and pH. The shelf life of yogurts at 1, 8, 15, 22, and 29 days of storage, as well as pH, acidity, syneresis, viscosity, viable lactic bacteria, and total coliforms were also assessed. In the second experiment, yogurts were submitted to lyophilization process, performed by scanning electron microscopy analysis and subsequently in those reconstituted, in addition to being assessed the physicochemical, rheological, and viable lactic bacteria characteristics. The results found in the first experiment showed that heat treatment was positive for viscosity, syneresis, and lactic bacteria, being viable until the 15th day of storage only for yogurts submitted to heat treatment. In the second experiment, lyophilization preserved the physicochemical characteristics of yogurts, but the number of initial lactic bacteria was different, also negatively affecting yogurt viscosity.

Influence of heat treatment on physicochemical and rheological characteristics of natural yogurts

The aim of this study was to assess the influence of heat treatment on physicochemical and rheological characteristics of natural yogurts, as well as the influence of lyophilization process on natural yogurts after reconstitution. In the first experiment, three yogurt treatments were processed, as follows: Treatment 1, yogurt produced with raw refrigerated milk; Treatment 2, yogurt produced with refrigerated pasteurized milk; and Treatment 3, yogurt produced with UHT (ultra-high temperature) milk, in addition to analyses of fat, protein, moisture, titratable acidity, and pH. The shelf life of yogurts at 1, 8, 15, 22, and 29 days of storage, as well as pH, acidity, syneresis, viscosity, viable lactic bacteria, and total coliforms were also assessed. In the second experiment, yogurts were submitted to lyophilization process, performed by scanning electron microscopy analysis and subsequently in those reconstituted, in addition to being assessed the physicochemical, rheological, and viable lactic bacteria characteristics. The results found in the first experiment showed that heat treatment was positive for viscosity, syneresis, and lactic bacteria, being viable until the 15th day of storage only for yogurts submitted to heat treatment. In the second experiment, lyophilization preserved the physicochemical characteristics of yogurts, but the number of initial lactic bacteria was different, also negatively affecting yogurt viscosity.

The influence of illuminance level on perception and willingness to buy during the tasting of sweetened natural yoghurt

This paper analyses the influence of the illuminance level of a light source on how consumers evaluated certain attributes of sweetened natural yoghurt and on their willingness to buy during product tasting. It also seeks to identify whether or not gender differences played a role in these evaluations. To do this, we conducted an independent within-subjects experiment (N=69) where illuminance level (low versus high) was studied. Participants had to assess one sensory attribute (‘Sweet’), three non-sensory attributes (‘Healthy’, ‘Natural’ and ‘Quality’) and willingness to buy for sweetened natural yoghurt. The results show that illuminance level influences the evaluation of some attributes and that there are discernible gender differences. In general, the consumers perceived the yoghurt to be healthier under low illuminance conditions and women perceived the yoghurt to be sweeter under high illuminance. Although the effects identified were not numerous, these findings suggest that illuminance level can influence consumers’ tasting experiences as well as their willingness to buy. The limitations of this research are discussed as well as their possible practical implications.

Development of Yoghurt with Juçara Pulp (Euterpe edulis M.) and the Probiotic Lactobacillus acidophilus La5.

Yoghurts are dairy products consumed worldwide and can be supplemented with substances that provide extra health benefits as well as probiotic strains. In this context, the present study aimed to prepare a yoghurt added of juçara (Euterpe edulis M.) pulp and the commercial probiotic strain Lactobacillus acidophilus La5. Moreover, the probiotic survival during storage and after in vitro exposure to simulated gastric and enteric conditions was evaluated. Four formulations of yoghurt were prepared: (a) natural yoghurt, (b) yoghurt added of probiotic, (c) yoghurt added of juçara pulp, and (d) yoghurt added of probiotic culture and juçara pulp. The preparations were evaluated for survival of probiotic strain during storage and its tolerance to gastric and enteric conditions in vitro. The probiotic population in yoghurt remained unchanged during 28days of storage. In addition, juçara pulp increased the probiotic resistance to simulated gastric and enteric conditions in the first day of storage. These data indicate that juçara pulp is a potential ingredient for the production of probiotic yoghurts.

Preference for naturalness of European organic consumers

Purpose The purpose of this paper is to provide insights into European organic consumers’ attitudes towards natural food and in their sensory preference for it. It explores whether there is any evidence for a latent dimension that represents consumers’ attitudes towards naturalness and which aspects can be assigned to this dimension. However, the main scope is to investigate whether attitudes towards naturalness are able to predict the liking of natural food. Design/methodology/approach Sensory tests of strawberry yoghurt are combined with consumer information obtained by means of a standardised questionnaire. About 1,800 organic consumers from France, Germany, Italy, the Netherlands, Poland and Switzerland were asked to blindly test two strawberry yoghurt samples that differed only in their absence/presence of an aroma additive. Findings On average, the consumers revealed a positive attitude towards natural food, but a negative sensory preference for the more natural yoghurt sample. Correlations between these two variables indicate that for most countries one cannot conclude that more naturalness-oriented consumers actually prefer the taste of more naturally flavoured yoghurts. This finding is interpreted as an attitude-liking gap. Research limitations/implications More research is necessary in order to clarify the reasons for the attitude-liking gap, since the authors can only speculate about these. Also, suitable data are needed to confirm the assumption made here that the naturalness of strawberry yoghurt can be determined by the degree of flavour intensity, especially against the background that the sensory skills of consumers are usually weak. Originality/value No attempt has been undertaken so far to test the claim that natural food products taste better and whether consumers with a positive attitude towards naturalness actually prefer the taste of a natural product over the taste of a more processed one. The present study attempts to fill this gap by exploring the preference for naturalness in a cross-national context.

Determination of estrogenic compounds in milk and yogurt samples by hollow-fibre liquid-phase microextraction-gas chromatography-triple quadrupole mass spectrometry.

An environmentally friendly method based on hollow-fibre liquid-phase microextraction (HF-LPME) was developed for the extraction of selected estrogenic compounds (i.e. four natural sexual hormones: estrone, 17β-estradiol, 17α-estradiol and estriol; two exoestrogens: 17α-ethynylestradiol and 2-methoxyestradiol; two synthetic stilbenes: dienestrol and hexestrol; and five resorcylic acid lactones: zearalenone, α-zearalanol, β-zearalanol, α-zearalenol and β-zearalenol), from whole cow and semi-skimmed goat milk and whole natural yogurt. After the optimization of the sample preparation procedure, spiked extracts were derivatized to their trimethylsilyl products using N,O-bis(trimethylsilyl)trifluoroacetamide reagent and then analyzed by gas chromatography-tandem mass spectrometry (GC-MS/MS). Once optimum extraction conditions were established (protein precipitation with acetonitrile, extraction and the back-extraction in acetonitrile following the HF-LPME procedure), the method was validated and the calibration range, precision and accuracy were studied. The RSD values for the intra- and inter-day precision of the peak areas were in the range 0.65-9.69 and 1.00-11.47%, respectively. The determination coefficients were higher than 0.991 for method calibration curves while LOD and LOQ values were between 0.06-2.55 and 0.16-6.11μg/L for whole cow milk, 0.04-1.70 and 0.11-4.86μg/L for semi-skimmed goat milk and 0.07-3.73 and 0.23-9.81μg/L for natural yogurt, respectively. Finally, the accuracy and precision of the method were evaluated, obtaining a value in the range 84 81-119% and RSD values lower than 20% in all cases.

Core-shell poly(dopamine) magnetic nanoparticles for the extraction of estrogenic mycotoxins from milk and yogurt prior to LC–MS analysis

In this work, core-shell poly(dopamine) magnetic nanoparticles synthesized in our laboratory have been applied as dispersive solid-phase extraction (dSPE) sorbent for the extraction of a group of six mycotoxins of interest including zearalenone, α-zearalanol, β-zearalanol, α-zearalenol, β-zearalenol and zearalanone, from complex matrices such as milk (whole and skimmed cow milk and semi-skimmed goat milk) and yogurt (an unsweetened natural yogurt) prior to their LC–MS analysis. 17β-estradiol-D5 was used as internal standard. The procedure includes a deproteinization step prior to the extraction procedure. Matrix-matched calibration and a recovery study were carried out in the selected matrices, providing good linearity, relative recovery values in the range 70–120% with RSDs lower than 16% and LODs between 0.21 and 4.77μg/L for milk samples and between 0.29 and 4.54μg/kg for yogurt samples.

Determination of Aflatoxins in Yogurt by Dispersive Liquid–Liquid Microextraction and HPLC with Photo-Induced Fluorescence Detection

A high-performance liquid chromatography (HPLC) method with fluorescence detection for the determination of aflatoxins B1, B2, G1, G2, and M1 in yogurt using dispersive liquid–liquid microextraction as alternative sample treatment has been developed. To enhance the fluorescence of aflatoxins B1 and G1, a post-column photochemical derivatization has been proposed, avoiding the use of derivatization reagents. The method was validated using natural yogurt as representative matrix, showing a good linearity in the studied range (25–500 ng kg−1) and limits of quantification below the maximum level established by European Union in milk for the manufacture of milk-based products. Satisfactory recoveries ranging from 69.4 to 99.7 %, with relative standard deviations lower than 11.2 %, were obtained for all the compounds. The proposed method is simple, rapid, with low solvent consumption, inexpensive, and environmentally friendly.

P125 “I googled it…”: what is recommended online for the management of vulvovaginal candidiasis?

<h3>Background</h3> Recently our centre encountered women reporting self-treatment of candidiasis with intravaginal applications of foodstuffs including garlic, vinegar and yoghurt. All patients had a unifying factor of reporting “googling” their therapy. <h3>Aim</h3> To establish which candidiasis management strategies female patients are most likely to encounter when searching via Google. <h3>Method</h3> Search history data was collated from Google Trends to identify the ten most popular search terms related to candidiasis in the UK between 15/03/15–06/03/16. These terms, along with term “thrush”, were assessed totalling 11 Google searches. All websites on the initial results page for each search term were accessed to review recommended therapies. Click-through data suggests the vast majority of Google users (&gt;90%) select their chosen website from this first results page. <h3>Results</h3> 116 search results included 97 (83.6%) advising women about vulvovaginal candidiasis. 96/97 (99%) recommended imidazole therapy first line, all reassuringly advising against oral therapy in pregnancy. Patients were recommended to seek treatment via a pharmacy (72, 74.2%) or their GP (54, 55.7%) rather than attending a genitourinary service (12, 12.2%). The recommendation of natural yoghurt for symptomatic relief was frequent (40, 41.2%), more than using emollients or soap substitutes (27, 27.8%). Unfounded treatments including eating probiotic yoghurts (9, 9.3%), vinegar (8, 8.2%), and treatment of sexual partners (8, 8.2%) were encountered. <h3>Conclusions</h3> Sensible evidence-based advice is the most prevalent online for vulvovaginal candidiasis. However a number of poorly evidenced therapies are encouraged. This information should be discussed and appropriately challenged during routine management of vulvovaginal candidiasis.

Interaction of starch and casein

Starch was commonly used to improve the stability of set yogurt. In this research, casein and modified starches were placed in a simulated yoghurt system giving the advantage of a low variation in the environment parameters compared to a natural yoghurt system. The interactions between modified starches (phosphate starch, hydroxypropyl starch and starch ester of octenyl succinic) and casein were investigated with several independed types of measurements methods. The combination of zeta potential and fluorescence micrograph were used to research the interactions between modified starches and casein. And the results proved that modified starches not only absorbed with casein via electrostatic forces, but also had steric stabilization. Besides this, fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were used to investigate the role of hydrogen bonds between modified starches and casein. It could be deduced that the interactions of modified starches and casein included electrostatic adhesion, steric stabilization and hydrogen bond. At the same time, electrostatic adhesion was the main interaction between phosphate starch and casein. The main role of the interactions between starch ester of octenyl succinic and casein should be steric stabilization.

Profile of lactic acid within validity of full natural yogurt

Univ Estadual Paulista UNESP, Fac Med Vet & Zootecnia, Dept Higiene Vet & Saude Publ, Campus Botucatu, Sao Paulo, Brazil

Avaliação sensorial de bebida láctea saborizada com pequi (Caryocar brasiliense)

Yogurt is a product widely commended for its sensory characteristics, nutritional and probiotic. The addition of fruits effectively increases the acceptance of the product, because not all consumers prefer the yogurt in its natural form, so the use of native fruits Yogurt flavored to provide an alternative food that may contribute to higher consumption of fruits and milk. The purpose of this study was to evaluate the acceptability of yogurt flavored with pulp pequi (Caryocar brasiliense). The survey was conducted at the Laboratory of Animal Products Unit of Animal Science Goiano IF - Green River Campus. The treatments were: T1 - Natural yogurt flavored with 4% pulp pequi T2 - Natural yogurt flavored with 8% of pulp and T3 pequi - Natural yogurt flavored with 12% pulp pequi. The yoghurts in the three treatments were submitted to a panel consisting of 51 untrained tasters of both sexes (male and female), recruited among students, faculty and staff of the Green River Campus IF Goiano. Statistical analysis was performed using the software-UFLA SISVAR ®. The best acceptability of dairy-based drinks pulp was pequi for concentrations of 4% and 8%. The manufacture of milk drink with the highest concentration of pulp pequi was not well accepted by the judges.

High-performance thin-layer chromatography analysis of steviol glycosides in Stevia formulations and sugar-free food products, and benchmarking with (ultra) high-performance liquid chromatography

A high-performance TLC (HPTLC) method was newly developed and validated for analysis of 7 steviol glycosides in 6 different types of food and Stevia formulations. After a minimized one-step sample preparation, 21 samples were developed in parallel, allowing an effective food screening. Depending on the sample application volume, the method was suited to analyze food sample concentrations in the mg/kg range. LOQs of stevioside in natural yoghurt matrix spiked at 0.02, 0.13 and 0.2% were determined by the calibration curve method to be 12ng/band (peak height). ANOVA was successfully passed to prove data homogeneity in the working range (30–600ng/band). The accuracy (recovery tolerance limit, 92–120%), repeatability (3.1–5.4%) and intermediate precision (4.0–8.4%) were determined for stevioside in milk-based matrix including sample preparation and recovery rates at 3 different concentration levels. For the first time, the recording of HPTLC–ESI-MS spectra via the TLC-MS Interface was demonstrated for rebaudioside A. HPTLC contents for rebaudioside A were compared with results of two (U)HPLC methods. The running costs and analysis time of the three different methods were discussed in detail with regard to screening of food products.

The yogurt amino acid profile's variation during the shelf-life.

To analyze the yogurt amino acid profile starting from marketing through the whole shelf-life. The evaluation of the proteolytic activity of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus, allows to deduce their vitality during the shelf-life period and within 45 days. Three types of full fats yogurts have been analyzed (a) natural white (b) sweet white and (c) whole fruit - in two stages: t0 (first day of shelf-life) and t1 (end of shelf-life). The proteins have been analyzed by the Kjeldahl method and the amino acid profile by HPLC. In natural yogurt a significant increase of the amount of free amino acids has been observed during the period of shelf-life (97%). In the sweetened full fats and fruit yogurt, instead, there is a lower increase of respectively 33% and 39% In whole milk natural yogurt, based on our data, the proteolytic activity seems to persist during the entire period of the shelf-life and this can be considered an index of bacterial survival, especially of Lactobacillus delbrueckii subsp. bulgaricus during the marketing process.

Yoghurts with addition of selected vegetables: acidity, antioxidant properties and sensory quality

Yoghurt is a fermented milk of unique sensory, nutritive and dietetic value offered in a variety of types and in different flavours. Vegetables belong to the group of food products rich in antioxidant substances (e.g., vitamin C, carotenoids, tocopherols, polyphenols) which regular consumption lowers the risk of many diseases including cancers and cardiovascular disorders. The aim of the present work was to manufacture and assess the acidity, sensory quality and antioxidant capacity of yoghurts with addition of selected vegetables during 2-week refrigerated storage. The vegetable preparations (carrot, pumpkin, broccoli and red sweet pepper) were added to the cow's milk fermented using DVS type yoghurt culture after initial cooling to 15-20°C in the amount of 10% (w/w). The following analyses were performed: determination of pH, titratable acidity, antioxidant activity by ferric reducing antioxidant power (FRAP) and 2,2'-diphenyl-1-picrylhydrazyl (DPPH) method as well as sensory evaluation and were conducted after 1, 7 and 14 days of cold storage. The yoghurt supplementation with selected vegetables had no significant effect on the pH and titratable acidity level. The highest ability to scavenge DPPH radicals was stated for yoghurts with broccoli and red sweet pepper. The latter treatment gained the highest notes in sensory evaluation. All vegetable yoghurts were characterised by higher than the natural yoghurt FRAP values measured directly after production. However, the level of this parameter significantly decreased after storage. The red sweet pepper additive was the most beneficial regarding antioxidant properties and organoleptic acceptance of the studied yoghurts.

Individual differences as predictors of dietary patterns among menopausal women with arterial hypertension.

IntroductionThe aim of this study was to analyze selected individual determinants of dietary choices, important for etiology and prevention of degenerative cardiovascular disorders, in a group of menopausal women diagnosed with arterial hypertension.Material and methodsThe study included a group of 160 women from the Małopolska region, aged between 45 and 60 years and diagnosed with arterial hypertension. A questionnaire assessing the frequency of food product consumption was used, along with standardized psychological tests (GSES, LOT-R, and SWLS). Spearman's coefficients of rank correlation and the Kruskal-Wallis and Dunn tests were used for statistical analysis.ResultsWe revealed that higher levels of self-efficacy were associated with more frequent consumption of whole grains, oatmeal, raw vegetables, fruit, semi-skimmed milk, natural yoghurt, marine fish, legume seeds, soy products, nuts, plant oils, and fruit and vegetable juices, as well as with less frequent consumption of whole milk, high-fat cottage cheese, and sweetened carbonated beverages and alcoholic beverages. The levels of optimism and satisfaction with life correlated positively with the consumption frequency of brown rice, whole grains, oatmeal, fruit, marine fish, legumes, soy products, nuts, butter, and fruit juices, and were inversely correlated with the consumption of white bread, high-fat cottage cheese, pork meat and sausages, and sweets and pastries.ConclusionsPostmenopausal women with arterial hypertension who were characterized by lower levels of self-efficacy, optimism, and satisfaction with life made less rational dietary choices which could negatively affect the efficacy of the secondary prevention of cardiovascular degenerative disorders.

Analysis of oestrogenic compounds in dairy products by hollow-fibre liquid-phase microextraction coupled to liquid chromatography

In this work, the potential of a hollow-fibre liquid-phase microextraction (LPME)-based method has been studied and validated for the extraction of a group of nine oestrogenic compounds four of them being natural (oestriol, 17β-oestradiol, 17α-oestradiol and oestrone), four being synthetic (17α-ethynyloestradiol, diethylstilbestrol, dienestrol and hexestrol) and one metabolite (2-hydroxyoestradiol) in different dairy products (whole and skimmed natural yogurt, a probiotic yogurt-type drink and cheese). The methodology includes a prior protein precipitation with acidified acetonitrile for all samples and an additional defatting step with n-hexane for cheese, the matrix with the highest fat content. Later separation, determination and quantification were done by high-performance liquid chromatography coupled to a diode array detector and a fluorescence detector set in series. Calibration, sensitivity, precision and accuracy of the method were carried out in the selected matrices, providing good linearity, LODs in the low μg/kg or μg/L range, good precision and appropriate accuracy.

Biogenic amines formation in Streptococcus thermophilus isolated from home-made natural yogurt

Twelve different biogenic amines formation in 58 isolates of Streptococcus thermophilus from home-made natural yogurt were investigated in histidine (HDB) and lysine decarboxylase broth (LDB). All S. thermophilus isolates had an ability to produce twelve different biogenic amines in HDB and LDB. Most of the S. thermophilus isolates formed low amounts of histamine (1–50mg/L) from histidine. Apart from one isolate, S. thermophilus produced tyramine at low (47 isolates) and medium (10 isolates) levels. The amount of each specific biogenic amine produced by S. thermophilus was generally lower than 100mgL−1. Also, the presence of hdcA gene was investigated using PCR technique and relation between gene and histamine production was conducted in S. thermophilus isolates. This study showed that most of the S. thermophilus isolates have the ability to form biogenic amines, especially histamine, and tyramine, which is an important consideration when selecting strains as starter cultures.