Natural Yogurt Research Articles

Examining the possibilities of applying high pressure to preserve yoghurt supplemented with probiotic bacteria

Natural yoghurt was subject to pressures of 200 and 250 MPa/4 and 18°C/15 min, after which milk-activated inocula of Lactobacillus acidophilus and Bifidobacterium sp. were added. The yoghurts were stored for 4 weeks at refrigeration temperature. After preparation and each week of storage, the count of bacteria, acidity, antibacterial property and an organoleptic assessment was determined. The highest survival rate was demonstrated by the bacteria of Lactobacillus delbrueckii ssp. bulgaricus, Streptococcus thermophilus and Bifidobacterium sp. in the yoghurt pressurised 200 MPa/15min at 4°C. Acidity increases in the control yoghurts were higher than in the pressurised ones. Pressurised yoghurts demonstrated weaker antibacterial effect in comparison to control yoghurts. Slight changes in the smell and taste were observed after pressurisation. Yoghurts pressurised at 18°C were characterised by more favourable organoleptic properties. Better conciseness of the curd and lower whey seep out were observed in pressurised yoghurt.

Aflatoxin M1 determination in yoghurt produced in Guilan province of Iran using immunoaffinity column and high-performance liquid chromatography

The present study was aimed to determine the presence and levels of aflatoxin M(1) (AFM(1)) in 120 natural yoghurt samples consisting of 80 samples of commercial and 40 samples of traditional yoghurt in Guilan province in the north of Iran. The occurrence and concentration range of AFM(1) in samples were determined by immunoaffinity column extraction and high-performance liquid chromatography. Analysis of yoghurts showed that all the samples were contaminated with AFM(1) in concentration levels ranging from 4.2 to 78.9 ng/kg. In general, 16 samples (13.33%) had higher AFM(1) level than the maximum tolerance limit (50 ng/kg) accepted by European Union, but the contamination level was lower than 500 ng/kg in all the samples, which is accepted by Codex Alimentarius and National Standard. The concentration of AFM(1) in 26 samples (21.66) was lower than 10 ng/kg. The range of contamination of AFM(1) was comparatively higher in traditional yoghurt (average concentration of 32.9 ng/kg) than that in commercial yoghurt (average concentration of 21.6 ng/kg; p < 0.01). Because yoghurt is the most popular dairy product consumed in Iran, the AFM(1) contamination is a serious problem for public health. This study reports the data of a first survey on the presence of AFM1 in yoghurt in Guilan, Iran.

Organic and conventional nonflavored yogurts from the Italian market: study on sensory profiles and consumer acceptability

The sensory properties of food products are an important success factor, especially in the organic market, where many producers and distributors of organic food claim superior taste for their products compared to the conventional alternative. For this reason consumer expectations and preferences, as well as the sensory properties of conventional and organic yogurt, have to be investigated in depth. In this work, the sensory profiling and consumer data of six nonflavored organic and conventional Italian yogurts were elaborated. Some results on the data segmentation (heavy and light users of organic food) and on the effect of information on liking (blind and labeled test) were obtained. Multivariate analysis was carried out to study how the sensory characteristics of 'natural yogurts' drive consumer liking. Consumers' preferences were oriented towards a creamy mouthfeel and smooth visual appearance and for a less acid and fresh taste. In particular, a conventional yogurt was the least accepted, because it was not creamy enough. This paper shows there is room to improve unflavored yogurt to better meet consumer expectations. Sensory profiling did not allow a distinction in odor/taste/texture between organic and conventional samples. However, three of four organic samples were in the region of highest consumer acceptability, fitting well consumers' preference. There was no clear tendency that heavy or light users scored differently in the blind and labeled tests regarding overall liking but, for all, the most liked conventional yogurt scored higher when labeled as organic.

Total contents of major minerals in the nature yoghurt and in the yoghurts with the date powder of three dry varieties

In this paper we report on the content of major minerals (calcium, magnesium, sodium, potassium, iron and zinc) in the nature yoghurt (without sugars) and three yoghurts added with date powders. The latter’s were from three dry date varieties (Mech-Degla, Degla-Beida and Frezza). The elements determination was carried out using atomic absorption spectrometry after mineralization processing. Total mineral content showed a great difference between the yoghurt nature and yoghurts enriched by date powder fruits. In the yoghurts added with date powder, following results were found (in mg/Kg): calcium (2213.31-2938.67), sodium (783.37-959.36), potassium (725.68-771.77), magnesium (169.54-267.85), iron (9.6-11.52), zinc (1.29-7.93). Concerning the natural yoghurt the values obtained were (in mg/Kg): calcium (1950.41), Sodium (684.72), potassium (540.58), magnesium (132.16), iron (5.26), zinc (0.35). These results are in positive interrelationship with those of the rheological properties.

Efectos de la suplementación con bloques multinutricionales a base de nopal fermentado sobre la ganancia de peso de ovinos en crecimiento

Este trabajo presenta una alternativa práctica del aprovechamiento del nopal mediante la elaboración de Bloques Multinutricionales (BM) y su utilización en la alimentación de corderos en crecimiento. Al nopal fresco picado se le adicionó sorgo, soya, urea, minerales y yogurt natural, se dejó fermentar por dos semanas a temperatura ambiente y se elaboraron los BM con un 25 % de nopal fermentado. Se utilizaron 20 corderos destetados con un peso vivo promedio de 17 Kg distribuidos en dos grupos (con y sin BM), ambos grupos recibieron una dieta típica. Durante 57 días de experimentación se midió el consumo de alimento, consumo de BM y el peso de los corderos. Los pesos de los animales fueron analizados estadísticamente mediante un análisis de varianza con un diseño completamente al azar. No se encontraron diferencias estadísticamente significativas (P &gt; .05) en los pesos de los animales. El BM elaborado con nopal fermentado fue consumido adecuadamente por los animales.

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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.

Quality characteristics of yogurt from goat's milk, supplemented with fruit juice

Yogurt was prepared from goat's milk, supplemented with aronia juice and blueberry juice. The dynamics of acidification, number of lactic acid bacteria, and fatty acids composition were investigated. Yogurt from goat's milk, supplemented with aronia juice and blueberry juice, coagulated at a lower acidity and faster than natural yogurt. The numbers of lactic acid bacteria in supplemented yogurts were higher compared to control samples. The addition of aronia and blueberry juices increased the amount of unsaturated fatty acids in yogurt by 6.9% and 8.5%, respectively. Polyunsaturated fatty acids increased by 11.2% in yogurt with aronia juice in comparison with natural yogurt.

Yoghurt impacts on the excretion of phenolic acids derived from colonic breakdown of orange juice flavanones in humans

Human urine was collected over a 24 h period after the consumption of 250 mL of (i) water, (ii) orange juice, and (iii) orange juice plus 150 mL of full fat natural yoghurt. The orange juice contained 168 micromol of hesperetin-7-O-rutinoside and 18 micromol of naringenin-7-O-rutinoside. GC-MS analysis of the urine identified nine phenolic acids, five of which, 3-hydroxyphenylacetic acid, 3-hydroxyphenylhydracrylic acid, dihydroferulic acid, 3-methoxy-4-hydroxyphenylhydracrylic acid and 3-hydroxyhippuric acid, were associated with orange juice consumption indicating that they were derived from colonic catabolism of hesperetin-7-O-rutinoside. The overall 0-24 h excretion of the five phenolic acids was 6.7 +/- 1.8 micromol after drinking water and this increased significantly (p < 0.05) to 62 +/- 18 micromol, equivalent to 37% of the ingested flavanones, following orange juice consumption. When the orange juice was ingested with yoghurt excretion fell back markedly to 9.3 +/- 4.4 micromol. This was not due to a difference in mouth to caecum transit time, as measured with breath hydrogen production, though possibly there may have been a slowing of the bulk of the meal reaching the large intestine which may then have altered the catabolism of the flavanones to phenolic acids by the colonic microbiota.

Freqüência do consumo de alimentos fontes de cálcio, entre crianças de 5 a 11 anos, de escola privada de Maringá/PR

School-aged children possess specific nutritional needs, demanding greater energetic amounts with appropriate vitamin and mineral contributions. The objective of this study was to evaluate the frequency of the intake of calcium-rich dairy products in schoolchildren between 5 and 11 years old at a private school in Maringa/PR. The data used belonged to the GREPO database; for economical classification, the ABEP Questionnaire was used; to evaluate the habitual consumption of milk and dairy products, a Food Frequency Questionnaire was used (QFCA). From the 308 evaluated students, 49.7% were boys and 50.3% girls; 49.7% were classified as being in economic class A2; 27.3% in class B; 0.6% in C and 1.0% in E; 61.2% of children consumed whole milk everyday; however, 26.5% reported they rarely or never consumed it; 17.2% consumed skim milk everyday; however, 71.6% of them rarely or never consumed this victual. On average, 11.5% of schoolchildren consumed fruit yogurt, fermented milk, yellow cheese, cream cheese and butter everyday. It was verified that victuals such as white cheese and natural yogurt are the least consumed. In this study, the schoolchildren reported the participation of the milk in their diet, with preference given to whole milk.

ELABORAÇÃO E AVALIAÇÃO DE IOGURTE SABOR FRUTOS DO CERRADO

Iogurtes com adição de doce de araticum, buriti, cagaita, jatobá, mangaba e pequi foram processados, verificando-se sua vida-de-prateleira, preferência e aceitação. Três formulações de iogurtes foram elaboradas, contendo 15%, 20% e 25% dos doces para os iogurtes de pequi e jatobá e 20%, 25% e 30% dos doces para os demais iogurtes. O doce dos frutos foi adicionado ao iogurte natural na temperatura de ± 20°C e homogeneizado. Após a preparação, as amostras foram resfriadas a ± 4°C e submetidas à análise de preferência. A amostra preferida foi submetida à análise de aceitação com 100 julgadores não-treinados com idade entre 8 e 65 anos, mediante escala hedônica de nove pontos. Verificou-se a vida-de-prateleira dos iogurtes elaborados durante 7 dias por meio de análise sensorial com equipe composta por 7 julgadores treinados, análise físico-química para verificação do pH e acidez titulável e análise microbiológica para verificação de coliformes totais, coliformes a 45°C, contagem de estafilococos coagulase positiva e presença de Salmonella sp. em 25 g. Os resultados indicaram boa aceitação dos iogurtes, sendo que o de sabor araticum (com 25% do doce) apresentou maior média (7,4). Já o iogurte sabor jatobá com 20% de doce revelou a menor média (5,49). As análises físico-químicas e sensoriais mostraram que os produtos apresentaram-se estáveis sob refrigeração durante 5 a 6 dias, caracterizando-os como produto de consumo rápido. As análises microbiológicas mostraram que as boas práticas de higiene foram adequadas para garantir a qualidade microbiológica dos produtos.

Quality Comparison of Probiotic and Natural Yogurt

The study was conducted to evaluate and compare the quality of probiotic and natural yogurt. Several samples of probiotic and natural yogurt were bought from supermarkets in Middlesborough (UK) and analyzed for physico-chemical, microbiologica l and organoleptic properties. Physico-chemical analysis showed that probiotic yogurts have more pH, fat and solid not fat (SNF) contents compared to natural yogurt. While natural yogurts have higher Total Titrable Acidities (TTA) and total solids contents, compared to probiotic yogurts. Organoleptically, probiotic yogurt was found more acceptable compared to natural yogurt. However, the fat contents of natural yogurt are lower and that might affect the overall acceptability of the yogurt. Similarly, an increase in the TA of the natural yogurt might affect the quality of the product. Microbiological analysis found no significant variation in total viable count between probiotic and natural yogurt.

Quality evaluation of yogurts produced commercially In Lagos, Nigeria

Yogurt of the natural-stirred and pineapple-stirred varieties manufactured commercially in Lagos, Nigeria were analyzed to evaluate the nutritional quality of the fresh and stored product. The carbohydrate and protein contents were higher in the pineapple than in natural yogurt with an average percent content of 12.7 and 1.2 compared to 7.0 and 0.9 respectively. The fat content was the same, about 1.0 percent of each type. These values decreased with time during storage and the decrease was more rapid at 30oC than at 10oC. Natural yogurt was more acidic with an average pH of 3.8 and 3.0% lactic acid content compared to values of 4.2 and 2.4% respectively for pineapple yogurt. Titratable acidity and moisture content increased with storage time without any marked change in pH. Yogurt spoilage was evident from the yeast odour when yeast counts had reached 106 -108 cfu ml-1. A product shelf life of 6 days at 10oC and 48h at 30oC is recommended and the concentration of milk solids should be increased in order to produce a more nutritious yogurt. Keywords: Yogurts, quality evaluation, Lagos, Nigeria AJAZEB Vol. 7 2005: pp. 78-82

Effects of heating temperature and fat content on the structure development of set yogurt

The structure formation of yogurt gels made from bovine pasteurized milk of various fat contents (0%, 1.5% or 3.5%) and prepared using natural yogurt as a starter was monitored by measuring the rigidity modulus ( G′) development by means of a dynamic U-tube rheometer of novel design. The results indicated that both the heating pretreatment of the milk and its fat content significantly affect the rate of gelation as well as the final rigidity attained by the gel. That is, the higher the heating temperature employed and the higher the fat content was, the faster the onset gelation appeared to be and the more rigid was the gel network formed. The shape of the gelation curves of yogurt samples made from milk, either with or without fat, heated at 80, 85, 90 or 95 °C for 1 min and fermented at 45 °C, showed three distinctive parts indicating that the yogurt gelation process took place in three consecutive stages. The results are discussed in the light of a proposed mechanism which could explain the above mentioned findings.

Comparison of proximate, mineral and vitamin composition of common Brazilian and US foods

Because food analysis is costly and laborious, analytical data are frequently borrowed from tables of developed countries and incorporated in tables of developing countries. Taking advantage of the new Brazilian table of food composition, which is based on representative national sampling and actual analyses, an attempt is made to gain an insight into the adequacy of this practice by comparing data from the Brazilian and US tables in terms of the proximate, mineral and vitamin composition of 19 selected foods, common to both countries. For proximate composition, data agreement is excellent for dry whole milk; good for condensed milk, dry nonfat instant milk and canned peas; and fairly good for black beans, milk chocolate, lentils, oats, long-grain white rice and wheat flour. Greater variation is seen with minerals and vitamins. In terms of minerals, agreement is very good only for dry whole milk, good for black beans and canned peas; fairly good with milk chocolate, lentils, wheat flour and natural yogurt. For vitamins, agreement can be considered good only for wheat crackers and yogurt and fairly good for condensed milk and dry whole milk. The comparison indicates that data may be borrowed for proximate composition provided the foods are equivalent. However, caution must be taken in borrowing data for micronutrients.

The quest for the ideal product: Comparing different methods and approaches

This study compares three widely used methods for product optimisation or development: the just about right (JAR) method, the conventional method and a variant thereof. Three independent samples of respondents evaluated five variations of natural yoghurt according to one of the three methods. Theoretically, JAR and the variant method differ in how they approach attribute deviations from ideal (directly versus indirectly). The fundamental difference between the conventional and the variant method are the ideal points (calculated versus measured directly). Overall, we found that the methods yield similar orders of ideal points despite their methodological dissimilarities. However, in terms of suggested directions for product improvement, substantial differences exist which suggests that statistical criteria are an insufficient basis for these decisions which needs to be complemented by managerial judgment on the size of the deviation.

Effect of addition of starches of different botanical origin on the yogurt gel properties

The aim of the present study was to estimate an effect of addition of different starches (potato, maize, waxy maize and tapioca) on the sensoric properties as well as selected physicochemical properties of set-style yogurts. Sensoric evaluation comprised: color, taste, smell, consistency and general appearance. pH value, titration acidity, degree of syneresis by centrifuge and FIL/IDF methods, content of acetaldehyde and diacetyl were also estimated. All analyses were done on fresh yogurts and after 1 week and 3 weeks of storage at 4?C. It was stated that natural (not supplemented with any starch) yogurt and that fortified with waxy maize starch were characterized with the best sensoric properties. Moreover the latter one was found to maintain the highest acetaldehyde level after 3 weeks of storage. Also maize starch influenced higher level of this aromatic compound. Generally starch additives resulted also in lower acidity of yogurts during the first period of cold storage. Products with maize and tapioca starches demonstrated the highest resistance to whey separation.

Chemical characterization, dry matter and crude protein ruminal degradability and in vitro intestinal digestion of acid and fermented silage from tilapia filleting residue

The objective of the present study was to evaluate the chemical characteristics, amino acids and fatty acids profiles, dry matter (DM) and crude protein (CP) ruminal degradability and rumen-undegraded protein digestible in the intestine (RUP D) of the tilapia filleting residue (TFR) and of the acid and fermented silage of tilapia filleting residue (ASTFR and FSTFR, respectively). The ASTFR was obtained by an acidification process with the addition of 0.02 L/kg TFR of sulfuric acid and 0.02 L/kg TFR of formic acid and the FSTFR was obtained by fermentation with the addition of 0.05 kg/kg TFR of natural yogurt, 0.15 kg/kg TFR of molasses and 0.003 kg/kg TFR of sorbic acid. A completely randomized design was used to characterize the fatty acids profile of the ASTFR and FSTFR and to determine ruminal degradability of DM and CP of ASTFR, FSTFR and fishmeal (FIME). The amino acids profiles of the ASTFR and FSTFR differed from TFR, but ASTFR and FSTFR were similar to each other. The fatty acids profiles of the ASTFR and FSTFR were similar to the TFR profile. The ASTFR showed a higher (P<0.05) saturated fatty acid content in comparison to the FSTFR. The effective degradability (ED) of the CP at solid passage rate of 0.05 h −1 of the ASTFR and FSTFR were of 0.76 and 0.81, respectively, which are higher (P<0.05) than the TFR value of 0.44. To the ASTFR and FSTFR lower values (P<0.05) were observed to RUP D of 13.5 and 18.8 g/kg, respectively, in comparison the FIME of 224.4 g/kg RUP. The ASTRF and FSTRF showed alteration composition chemical and amino acids profile without altered the nutritive value of TFR. The processes of acidification or fermentation are methodologies that can be used as a conservation procedure of tilapia filleting residue.

Relative importance of texture properties in the sensory quality and acceptance of natural yoghurts

The aim of the study was to evaluate the influence of sensory and texture properties of natural yoghurts on their overall sensory quality and acceptability. Samples were evaluated by consumers, and a parallel quantitative descriptive analysis (QDA) was carried out, including analysis of thickness and smoothness. Results were analysed by principal component analysis (PCA). Measurements of yoghurt viscosity were carried out using Brookfield instruments. Sensory texture properties (thickness and smoothness) were not significantly correlated with yoghurt consumer acceptability. Viscosity measured instrumentally correlated well with sensory thickness. Negative sensory attributes (especially off‐flavour and bitterness) were of critical importance for consumer acceptance.

Survey of selected chemical and microbiological characteristics of (plain or sweetened) natural yoghurts from the Italian market

Selected chemical and microbiological characteristics of plain (n = 11) or sweetened (n = 11) natural stirred yoghurts collected in the Italian market were evaluated. A strong imbalance (1:103 to 1:105) between viable cell counts of Lactobacillus delbrueckii ssp. bulgaricus (LB) and Streptococcus thermophilus (ST) was observed in five sweetened samples. Unlike the plain sam- ples, lactic acid content was higher than that of residual galactose, suggesting the possible involve- ment of either galactose or added sugar in microbial catabolism. Nevertheless, isotope ratio mass spectrometry of lactic acid and sugars isolated from two sweetened samples resulted in a similar 13 C/ 12 C ratio for lactic acid and lactose, thus suggesting the catabolism of this disaccharide only. A significantly (P < 0.001) lower level of galactose characterised sweetened yoghurts with respect to plain ones. This feature was not related to significant production of exopolysaccharides by yoghurt bacteria since these compounds were not detected in any of the analysed sweetened samples. Pectin or starch were detected in three sweetened yoghurts despite the fact that addition of thickener to the milk base is not permitted by Italian regulation. Levels of furosine ranged from 44 to 208 mg·100 g -1 protein, suggesting that milk for yoghurt manufacturing is sometimes over-heated. In this regard, evaluation of heat damage could be an additional parameter to characterise yoghurt quality. Sweetened yoghurt / thickener / heat damage / isotope ratio mass spectrometry