Yogurt Aroma Research Articles

A comparative study to determine the key aroma components of yogurt aroma types based on Sensomics and Flavoromics

This study used Sensomics to examine four previously obtained yogurt aroma type profiles. 14 key aroma-active compounds were identified as significant contributors (p ≤ 0.05) in the four aroma types using gas chromatography–mass spectrometry-olfactometry (GC–MS/O), aroma extract dilution analysis (AEDA), odor activity values (OAV), and aroma recombination and omission experiments. The Sensomics and previous Flavoromics results were compared, showing that Flavoromics identified 10 indicator compounds for distinguishing aroma types. Eight were the same as the key aroma-active compounds identified via Sensomics, namely acetic acid, pentanoic acid, decanoic acid, 3-hydroxy-2-butanone, 2,3-pentanedione, acetaldehyde, δ-decalactone, and dimethyl sulfone. Sensomics revealed a prominent similarity between the categories of key aroma-active compounds of the four aroma types, with a higher sensory contribution. Flavoromics showed less overlapping between the indicator compounds, mainly related to the distinction between the four aroma types. Sensomics and Flavoromics serve distinct research objectives and should be selected according to the study subject.

Organoleptic Quality Evaluation of Peranakan Etawa Goat Milk Yoghurt (Capra Aegagrus Hircus) with the Addition of Mango Golek (Mangifera indica)

Yoghurt is a drink made from raw milk which has been fermented using a starter which has a slightly thick texture with a slightly sour taste. The purpose of this study was to determine the effect of golek mango juice on the color of yogurt, the texture of yogurt, the taste of yogurt and the aroma of yogurt in the Etawa crossbreed goat's milk by conducting an assessment in organoleptic testing of panelists. This research was conducted at the Laboratory of the Faculty of Agriculture and Animal Husbandry, University of Tjut Nyak Dhien Medan from May to June 2023. The study was conducted using the Kruskall Wallis method with 4 treatments, namely P0 (without golek mango juice), P1 (150 ml/4 g of golek mango juice), P2 (200 ml/6 g of golek mango juice), and P3 ( 250 ml/8 g of golek mango juice) with organoleptic tests consisting of color, texture, taste and aroma. The results showed that the addition of mango juice did not significantly affect the color, texture, taste and aroma of yogurt, however 8 g of mango juice in yoghurt showed the best preference. In conclusion addition of 8 g of golek mango juice is preferred by panelists

Improvement of sensory characteristics of Barangan banana (Musa acuminata Linn.) slices as a stirred yogurt topping

This study aimed to improve the sensory characteristics of bananas (Musa acuminata Linn.) slices as a stirred yogurt topping. Ascorbic acid was used in three different concentrations (C; 1%, 2%, and 3%) at three different soaking times (T; 4 mins, 5 mins, and 6 mins). Samples without soaking in ascorbic acid were used as a control. The sliced bananas were analyzed for color (brightness, L*; redness, a*; and yellowness, b*) and hedonic test (taste, aroma, and color) of 30 semi-trained panelists. The most preferred sample was then analyzed by descriptive test (taste, aroma, and color). The results showed that panelists mostly liked the slices banana soaked in 2% of ascorbic acid for 4 minutes. It had a strong sour taste, yogurt aroma, and brownish yellow color. The color values of the preferred sample of L*, a*, and b* were 98.1, -13.9, and +47.3 respectively. On the other hand, the control sample had sour taste, banana aroma, and blackish yellow color. The color values of the control sample of L*, a*, and b* were 94.2, -10.03, and 37.9 respectively. These results indicate that ascorbic acid could increase the appearance of Barangan banana as a stirred yogurt topping.

Machine learning based classification of yogurt aroma types with flavoromics

Traditional sensory evaluation, relying on human assessors, is vulnerable to subjective error and lacks automation. Nonetheless, the complexity of human sensation makes it challenging to develop a computational method in place of human sensory evaluation. To tackle this challenge, this study constructed logistic regression classification models that could predict yogurt aroma types based on aroma-active compound concentrations with high classification accuracy (AUC ROC > 0.8). Furthermore, indicator compounds discovered from feature importance analysis of classification models led to the derivation of classification criteria of yogurt aroma types. Through constructing and analyzing machine learning models on yogurt aroma types, this study provides an automated pipeline to monitor sensory properties of yogurts.

Rapid prediction of the aroma type of plain yogurts via electronic nose combined with machine learning approaches

The unique aroma attributes of yogurts are associated with their quality and consumer acceptance. However, the aroma types of plain yogurts and methods for quickly identifying them have not been systematically established. This study used quantitative descriptive analysis (QDA) to label the aromas of commercial plain yogurts into four primary types, namely fermented, cheesy, milky, and fruity, for the first time. Electronic nose (e-nose) data were rapidly collected from the headspace of plain yogurt samples, and the aroma types classification models were established using linear discriminant analysis (LDA), logistic regression (LR), support vector machine (SVM), and decision trees (DT). Among these models, the SVM-based model displayed the best classification performance, with accuracy and F1 values at 0.933. Furthermore, this study revealed that the LR classification model, based on refined smaller-size e-nose datasets, improved the accuracy and F1 values to 0.867 and 0.872, respectively, compared to the original LR model using the complete dataset, thus demonstrating the applicability of model simplification. This work provides a theoretical basis for rapid plain yogurt aroma type identification by combining e-nose data with machine learning approaches.

Effects of milk fat substitution by canola oil on the properties of high-fat high-protein yoghurt

High-fat high-protein yoghurts [9% fat, 8.2% protein (w/w)] with substitution of milk fat by canola oil were produced. The effects of milk fat substitution (0–100%) and milk homogenisation pressure (10 or 35 MPa) on the texture, syneresis, and rheological properties were evaluated. The aroma profile after 0, 14, and 28 days of storage (5 °C) was also determined. Increasing the proportion of canola oil reduced the firmness and increased the syneresis of yoghurt, but had no effect on the elastic and viscous modulus at 1 Hz. Increasing milk homogenisation pressure increased yoghurt firmness, elastic and viscous modulus, and apparent viscosity because smaller droplets were better embedded into the yoghurt structure. The substitution of milk fat by canola oil and storage time affected the yoghurt aroma profile. Some impacts of milk fat replacement by canola oil could be overcome using a higher homogenisation pressure.

Soya Yoghurt Organoleptic Test With The Addition of Rosella Flower Extract

The unpleasant aroma of soy juice drinks causes not everyone to like it even though they know that the drink is healthy. Several studies have carried out efforts to overcome this condition, such as adding aromas, flavors, and fermentation. In this study, the effort to eliminate the unpleasant aroma was carried out through the fermentation process of soybean juice into soya yogurt accompanied by the addition of rosella extract. There are six levels of addition of rosella flower extract, namely from R0 (0%), R1 (10%), R2 (15%), R3 (20%), R4 (25%), and R5 (30%), with a fermentation process the same one. An organoleptic test was conducted on 30 selected panelists who like yogurt. The test uses a hedonic scale of 5 responses (very much like, like, quite like, dislike, and do not like). This study found that the addition of rosella flower extract eliminated the unpleasant aroma of soybean juice and the distinctive aroma of yogurt, thereby reducing consumer preference responses. The panelist's highest preference for color was in the R5 treatment. The addition of too much rosella extract concentration will cause the soy yogurt taste to be too sour, so the addition of rosella extract is recommended to be sufficient at 10% - 20%.

Modulating microbiota metabolism via bioaugmentation with Lactobacillus casei and Acetobacter pasteurianus to enhance acetoin accumulation during cereal vinegar fermentation

Acetoin, giving a creamy yogurt aroma and buttery taste, exists in cereal vinegar as an important flavor substance and is mainly produced by the metabolism of Lactobacillus and Acetobacter during multispecies solid-state acetic acid fermentation. However, the impacts of Lactobacillus-Acetobacter interactions on acetoin accumulation and the microbial metabolism during acetic acid fermentation are not completely clear. Here, six strains isolated from vinegar fermentation culture and associated with acetoin metabolism, namely, Lactobacillus reuteri L-0, L. buchneri F2-6, L. brevis 4–20, L. fermentum M10-7, L. casei M1-6 and Acetobacter pasteurianus G3-2, were selected for microbial growth and metabolism analysis in monoculture and coculture fermentations. Lactobacillus sp. and A. pasteurianus G3-2 respectively utilized glucose and ethanol preferentially. In monocultures, L. casei M1-6 (183.7 mg/L) and A. pasteurianus G3-2 (121.0 mg/L) showed better acetoin-producing capacity than the others. In the bicultures with Lactobacillus sp. and A. pasteurianus G3-2, biomass analysis in the stationary phase demonstrated that significant growth depressions of Lactobacillus sp. occurred compared with monocultures, possibly due to intolerance to acetic acid produced by A. pasteurianus G3-2. Synergistic effect between Lactobacillus sp. and A. pasteurianus G3-2 on enhanced acetoin accumulation was identified, however, cocultures of two Lactobacillus strains could not apparently facilitate acetoin accumulation. Coculture of L. casei M1-6 and A. pasteurianus G3-2 showed the best performance in acetoin production amongst all mono-, bi- and triculture combinations, and the yield of acetoin increased from 1827.7 to 7529.8 mg/L following optimization of culture conditions. Moreover, the interactions of L. casei M1-6 and A. pasteurianus G3-2 regulated the global metabolism of vinegar microbiota during fermentation through performing in situ bioaugmentation, which could accelerate the production of acetic acid, lactic acid, acetoin, ethyl acetate, ethyl lactate, ligustrazine and other important flavoring substances. This work provides a promising strategy for the production of acetoin-rich vinegar through Lactobacillus sp.-A. pasteurianus joint bioaugmentation.

The effect of mixing temperature on the flavour expression of processed cream cheese

Although manufacturing conditions affect the texture of processed cheese, the effects of manufacturing conditions on flavour expression, and the mechanisms for these effects are unknown. This study investigated the effects of mixing temperature on the flavour expression of processed cream cheese and aimed to determine whether the content of aroma compounds in the matrix, the texture, and hydrophobic interactions between aroma compounds and the matrix contribute to flavour expression. Four model cheeses with mixing temperatures of 30 °C, 60 °C, 75 °C, and 88 °C were prepared. Sensory analysis, volatile aroma compound evaluations using HS-SPME and SAFE-GC/MS, texture analysis, microstructure observation, and hydrophobicity evaluation were conducted. The result showed that the decrease of scores for perceptions of “Yoghurt aroma”, “Acidity”, and “Acetic aroma” with increasing mixing temperature was due to the generation of aroma compounds. The decrease in scores for “Overall flavour intensity” was due to the product's hardened texture.

The Effect of Skim Milk Concentration on Sensory Quality and pH of Probiotic Yoghurt Added with Red Dragon Fruit (Hylocereus polyrhizus)

Probiotic yog h urt is one of dairy product s that has benefits to the human health . This research aim ed to understand the effect of skim milk concentration on the sensory quality traits and pH of probiotic yoghurt added with red dragon fruit ( Hylocereus polyrhizus ) dices prior to the fermentation. The research method was experimental method with 4 treatments and 3 replications in a completely randomized group design. The data were analyzed using one-way analysis of variance followed by D uncan ’s multiple range test at P<0.05 . The t reatment in this research was different addition levels of skim milk (3% , 5% , 7% , and 9%) to yoghurt . The pH , color, aroma, taste, texture, viscosity and overall acceptance were assessed . The addition of skim milk increased (P<0.05) the acceptability of flavor, texture, viscosity and overall acceptance, in which the addition of skim milk at 9% showed the highest acceptability of taste. However, different addition level of skim milk did not significantly affect pH and the acceptability of color and aroma of yoghurt. The pH of yogurt ranged from 4.06 to 4.26. In addition, the color and aroma of yogurt were in the scale of neither like or dislike , the texture was i n the scale of d islike to l ike, taste, viscosity and overall acceptance we re i n the scale of dis like to neither like nor dislike . In conclusion, skim milk should be used for producing yogurt with red dragon fruit at 9% of whole milk to obtain acceptable product .

The influence of almond flour, inulin and whey protein on the sensory and microbiological quality of goat milk yogurt

A set of six formulations of goat yogurt added with mix of starter (Lactobacillus bulgaricus and Streptococcus thermophilus), inulin, almond flour and whey protein have been evaluated in Italy and Czech Republic by microbiological and sensory analyses. The yogurt were prepared in the two laboratories involved in testing using the same raw materials found on the Italian market and provided to Czech researchers. The panel of each country separately defined sensory profiles by applying the same methodology. The results had shown a different discrimination of samples: the Italian panel, habitual consumer of goat dairy products, discriminated samples for goat yogurt aroma and flavor; the Czech panel, used to consume fermented milk, discriminated samples for acid descriptor. For both the panels, the addition of inulin was assessed as irrelevant, while the addition of whey was assessed as relevant. The addition of prebiotics, almond flour and inulin, did not affect microbial counts.

Aktivitas Antioksidan Dan Kualitas Organoleptik Yogurt Susu Kambing Etawa Dengan Sari Buah Bit (Beta vulgaris L.)

The study aims to determine the effect of the addition of beet juice concentration according to the treatment of antioxidant activity and organoleptic quality of etawa goat milk yogurt. The process of research and organoleptic testing was carried out at the Integrated Laboratory of Muhammadiyah University Purworejo and the antioxidant activity test at a private laboratory in Yogyakarta. The material used was 5 liters of etawa goat milk, 1/2 liter beet juice and bacteria Lactobacillus bulgaricus and Streptococcus thermopilus, samples were taken of 125 plastic containers with a contents of 25 ml/sample for organoleptic tests and 20 bottles with 30 ml contents/sample for antioxidant activity test. The treatments given were S0 (0%), S5 (5%), S10 (10%), S15 (15%) and S20 (20%). The method used was a completely randomized design (CRD) with 5 treatments and 4 replications. Parameters measured were antioxidant activity and organoleptic quality (color, aroma, taste, and texture). The results showed the treatment of the concentration of the addition of beet juice was significantly different (P 0.05) on the aroma, taste, and texture of yogurt. The results of antioxidant activity were 17.00, 27.25, 36.17, 40.34, and 45.01. Yogurt color values ​​of 1.48, 3.16, 3.04, 4.08 and 4.60. The value of yogurt aroma is 2.40, 2.72, 2.64, 2.68 and 3.08. The value of yogurt is 1.96, 1.72, 1.88, 2.40, and 2.48. Yogurt texture values ​​of 2.68, 2.84, 3.36, 3.28 and 3.60. Beet juice can increase the value of the antioxidant activity and organoleptic quality between treatments but not too significantly (P> 0.05) on the results of organoleptic tests on the aroma, taste, and texture parameters. Further beetroot research needs to be done.

YOĞURT MATRİKSİNİN TÜKETİM SIRASINDA IN VIVO AROMA SALINIMI ÜZERİNE ETKİLERİ

Aroma, tüketicilerin yoğurt tercihlerini etkileyen ana etkendir. Gıdayı tüketirken oluşan aroma algısı, ağızda salınan aroma bileşiklerinin gıda matriksi ve insan tükürüğü arasındaki etkileşimlerine bağlıdır. Yapılan araştırmalar, aroma algısının ve yoğurttan in vivo aroma salınımının birçok faktörden etkilendiğini göstermiştir. Yağ bileşeninin, yoğurdun aromasının tutuklanmasında ve algılanmasında önemli rolü vardır. Özellikle yağı azaltılmış yoğurtlarda, aromanın kontrollü salınmasını desteklemek için ilave edilen protein, yağ, aroma tutuklayıcı bileşenlerin, kıvam verici maddelerin ve tatlandırıcıların in vivo aroma salınımı ve aroma algısı üzerine farklı etkileri vardır. Bununla birlikte yoğurdun formüle edilmesi sırasında değişen tekstür de ağızda aroma salınımını etkilemektedir. Yoğurtta aroma algısı üzerine etki eden faktörleri anlamak, gıda sanayinde yenilikçi ve kabul gören gıda ürünleri üretmede önemlidir. Bu derlemede yoğurdun in vivo tüketimi sırasında matriksin etkisini ortaya koyan çalışmalar incelenmiştir.

Evaluation of pH, titratable acidity, syneresis and sensory profiles of some yoghurt samples from the Kingdom of Lesotho

A total of nine yoghurt samples purchased from the Kingdom of Lesotho were evaluated for their pH, titratable acidity, syneresis and sensory profiles following standard procedures. The pH, titratable acidity and syneresis of these nine samples were found to be in the range of 3.94-4.22, 0.69-1.81 and 1.76-35.15%, respectively. The sensory profiles such as appearance, texture, aroma, flavour, taste and overall acceptability of these nine samples were found to be in the range of 2.5-4.5, 2.2-3.3, 2.5-4.1, 1.7-4.0, 2.1-4.3 and 2.3- 3.9, respectively. The pH of all nine yoghurt samples was complying in accordance with FDA specifications. The percentages of titratable acidity of some yoghurt samples were complying in accordance with FDA specifications and some samples were not. On the other hand, some samples have remarkably high syneresis. Our study showed that the pH, titratable acidity, syneresis and sensory profiles of these yoghurt samples were significantly different (p&lt;0.05). Sensory properties, particularly, flavour, taste and aroma of yoghurt samples are needed to be improved for a better consumer overall acceptability. To the best of our knowledge, this is the first report of this kind on yoghurt samples from the Kingdom of Lesotho.

PEMANFAATAN KULTUR BAKTERI ASAM LAKTAT (BAL) Lactobacillus bulgaricus dan Streptococcus thermophilus DALAM PEMBUATAN LULUR

The majority of body scrub that are distributed in the market contain paraben. Paraben is a type chemicals that are safe to use in the appropriate amount. But it could cause skin irritation. This research was conducted to know the durability from natural body scrub by yogurt and rice flour without chemical preservative and safe for skin. The research methods are comparison of the use of Lactobacillus bulgaricus and Streptococcus thermophilus with concentration 25:25; 30:20; 20:30. The yogurt will be mixed with rice flour and the treatment control using factory yogurt with concentration of rice flour comparing with yogurt namely 10:14; 10:16; 10:18. This product was tested to 50 panelists. This product was kept in room temperature ±28oC for a month and conducted the identification of microbial impurities that contaminate the product with Gram staining method and catalase test. Data was analyzed by analysis of variance (ANOVA). Starter with different comparison 25:25, 30:20; 20:30 are not making real difference. All of the treatment produce yogurt with typical aroma of yogurt, white colored, and soft texture. The formula in K2 (10:16) treatment with the highest average that obtained 3.38 (very like) in color parameter and 3.08 (very like) in texture parameter. Although in aroma parameter the average value that obtained is 2.79 (like). In A1, A2, and B2 treatment had the highest durability percentage that obtained 83,3% and the lowest was shown in K1 and K3 treatment that obtained 0%. Microbial impurities that identified was bacteria from Genus Bacillus and Genus Streptobacillus, fungal impurities from Genus Aspergillus, Rhizopus, and Trichoderma.&#x0D; &#x0D; Keywords : lactic Acid bacteria, yogurt, Lactobacillus bulgaricus, Streptococcus thermophilus, body scrub&#x0D;

Effects of floral honey and pressed flax seeds on intensity of yogurt aroma, sweetness and sour taste of yogurts during storage

The aim of this study was to evaluate chosen sensory properties of yogurts without any additions of honey and pressed flax seeds (K) and with the different addition of floral honey (1, 3 and 5%) and with the same addition (0.5%) of pressed flax seeds (PA, PB and PC) during storage. These samples were analysed during 14 days of storage at cooling temperature (6 ±1 °C). Sensory properties - intensity of yogurt aroma, sweetness and sour taste were evaluated. Sensory evaluation was carried out in the 1st, 7th and 14th day following the yogurts production. The control samples had the most significant yogurt aroma this sample had also the highest sour taste and the lowest sweet taste throughout the storage. In all of analysed samples, the sourest taste was observed 14th day of storage. The sweet taste of yogurts with honey addition increased compared to control samples however the sweetest taste of samples with addition of honey was 1st day following the yogurt production. Optimum sweetness was determined with the samples of yogurts containing 5% of floral honey. Floral honey added into the yogurts has positive effect on their sensory properties. The pressed flax seeds have no effect on sensory properties of yogurts. The enrichment of yogurts with honey and pressed flax seeds is high recommended because they have a lot of beneficial nutritional properties and improve the sensory quality of the final product.

DAYA TERIMA DAN TOTAL COST KOMBINASI SARI KULIT BUAH NAGA MERAH DAN SARI BUAH JAMBU BIJI MERAH

Antioxidant plays a role as the free radical savaging. The red guava and the red dragon fruit peel contain high antioxidants so it is potentially to be a functional product. The aim of this study was to analyze the effect of red guava juice and red dragon fruit peel essence addition on yoghurt acceptability and total cost. The research used a factorial design of 5 repetitions on 5 formulas. There are 1 control formula (F0) and 4 modifi cation formulas (F1, F2, F4, F5) with the addition of red guava juice and red dragon fruit peel. The panelist on this research consist of 30 untrainedpanelists. Descriptive analysis and inferential statistic using Friedman and Wilcoxon Sign Rank Test with α = 0,05 were used to analyze the difference of acceptability between the formulas. Panelists showed that the best treatment was F4 yoghurt formula (44% addition of fruit juice with the ratio of guava juice and red dragon fruit peel 50:50) and it has the most preferred acceptability (color, aroma, texture, and taste) with the average value was 2.91 and food cost per serving (100 ml) was Rp 2.900,00. Formula F4 has a good acceptability and lower total cost than commercialyoghurt. This formula has a potential to be an alternative functional drink. The aroma of yoghurt can be increased by eliminate cooking process on the red dragon fruit peel juice.Keywords: acceptability, red guava, red dragon fruit peel, total cost, yoghurt

Draft Genome Sequence of Lactobacillus delbrueckii subsp. bulgaricus LBB.B5.

Lactobacillus delbrueckii subsp. bulgaricus LBB.B5 originates from homemade Bulgarian yogurt and was selected for its ability to form a strong association with Streptococcus thermophilus. The genome sequence will facilitate elucidating the genetic background behind the contribution of LBB.B5 to the taste and aroma of yogurt and its exceptional protocooperation with S. thermophilus.

Identification, typing and functional characterization of dominant lactic acid bacteria strains from Iranian traditional yoghurt

Interest in the microbiota of traditional fermented dairy products, such as yoghurt, continues due to the need for new lactic acid bacteria (LAB) strains that can complement or replace currently-in-use starters. In this work, five traditional yoghurts and one milk sample (for making yoghurt) from different areas of the Khorasan-e-Razavi region, Iran, were subjected to microbial characterization. Among the 102 isolates recovered, which included 29 from milk, the thermophilic LAB species Streptococcus thermophilus (34) and Lactobacillus delbrueckii (36) (with similar numbers of the subsp. bulgaricus and lactis) were the majority bacteria in all samples. Wide intra-species phenotypic and genetic diversity was encountered among the isolates. The safety and technological features of 29 strains belonging to the species S. thermophilus, L. delbrueckii and Lactobacillus helveticus, all candidates for use in yoghurt-making, were examined. In culture, two S. thermophilus strains produced the biogenic amine histamine from histidine (its precursor amino acid), and five L. delbrueckii strains showed atypical resistance to tetracycline (MIC ≥ 8 μg mL−1). The remaining strains coagulated milk, producing a coagulum of good appearance and pleasant acidic aroma. None of them produced appreciable amounts of exopolysaccharides in milk under the incubation conditions. After fermentation of milk with individual and mixed strains, major yoghurt aroma volatile compounds (i.e. acetaldehyde, diacetyl and acetic acid) were detected. Also as being used in the design of commercial starters, the thermophilic LAB strains characterized in this study might be used to help improve the safety of traditional yoghurts, while maintaining their original qualitative and sensorial characteristics.

Monitoring of lactic fermentation driven by different starter cultures via direct injection mass spectrometric analysis of flavour-related volatile compounds

In this work, we used Proton Transfer Reaction-Mass Spectrometry (PTR-ToF-MS), coupled with an automated sampling system, to monitor lactic fermentation driven by different yogurt commercial starter cultures via direct injection mass spectrometric analysis of flavour-related volatile compounds. The aim is the identification of markers for real-time and non-invasive bioprocess control and optimisation as an industrial driver of innovation in food technology and biotechnology. We detected more than 300 mass peaks, tentatively identifying all major yogurt aroma volatiles. Thirteen mass peaks showed statistically significant differences among the four commercial starters. Among these are acetaldehyde, methanethiol, butanoic acid, 2-butanone, diacetyl, acetoin, 2-hydroxy-3-pentanone/pentanoic acid, heptanoic acid and benzaldehyde which play a key role in yogurt flavour. These volatile described the diverse flavour properties claimed by food biotechnological companies and, considering the possible contribution to yogurt flavour, are potential markers for the rapid screening of starter cultures and for the quality design in this fermentation-driven production. The strength of our approach lies in the identification, for the first time, of specific depletion kinetics of four sulphur containing compounds occurring during fermentation (hydrogen sulphide, methanethiol, S-methyl thioacetate/S-ethyl thioformate, pentane-thiol), which suggest a new possible protechnological feature of yogurt starter cultures.