Probiotic fermented oat dairy beverage: viability of Lactobacillus casei, fatty acid profile, phenolic compound content and acceptability

Abstract

The combination of oats such as water-soluble oat extract (SOE) and probiotic microorganisms can add nutritional value to the food and benefits to the consumer’s health. The SOE contains soluble fiber, whose major soluble fraction is composed of β-glucan contains soluble antioxidants such as ferulic acid, avenanthramides and other phenolic acids. The purpose of this study was to develop a fermented dairy beverage containing SOE, evaluating the viability of the probiotic culture, the fatty acid profile, phenolic compounds content and sensory characteristics during the storage. It was verified that Lactobacillus casei remained viable during the 21 days of storage (count above 7 Log CFU.mL⁻¹) and that the addition of SOE does not affect the viability of probiotic bacteria. The levels of bioactive compounds soluble in aqueous medium, increased between the beginning of the experiment and the end, being influenced by the addition of SOE. Seven fatty acids were found in all formulations with a prevalence of C16:0 followed by C18:1. The addition of SOE in the formulation contributes to a significant increase in linoleic acid (C18:2n6). The sensory evaluation of the fermented oat dairy beverage with L. casei (BAC) was positive: the product was highly appreciated by consumers, with acceptance rate of 84.4%. The combination of SOE, with L. casei in the production of novel probiotic fermented dairy beverage, was technologically feasible, improving the functional properties of the product and offering health benefits to the consumer. More studies should be made to evaluate the composition and functional properties of SOE.

Introduction

Products that are nutritional and beneficial to human health, called functional foods, are the focus of investments in the food industry. The search for new products is increasing, especially the ones combining fermented dairy products with fruits and cereals. Among cereals, oats are considered an important source of nutrients, containing proteins (high level of lysine), unsaturated fatty acids, and phytochemicals and fiber fractions necessary for a balanced human diet (Zhang et al. 2015). In addition, they have been recognized as a source of β-glucan and antioxidants, especially phenolic compounds (Wang et al. 2014), being applied to several products available in the market.

Cereals offer an alternative to the production of functional food, since they can be used as a fermentable substrate for the growth of probiotic microorganisms. In Brazil, it is permitted to add whey in the production of dairy beverage (Brasil 2005), which has excellent functional properties of whey proteins. The addition of vegetable extract as a substitute for milk is also allowed, and these alternatives can diversify the dairy market.

The trend of the marketing of probiotic dairy products is increasing among consumers, since they are well accepted and recognized as beneficial to human health. By definition, probiotics are living microorganisms which, when administered in suitable amounts, confer benefits to host health (FAO/WHO 2001).

However, for the microorganism to confer benefits to the host, some characteristics are necessary, such as tolerating human gastric acid and juice; bile tolerance (survival in the small intestine); adherence to the epithelial surface and persistence in the human gastrointestinal tract; immunostimulation; antagonist activity against pathogens; antimutagenic and anticarcinogenic properties (Mitropoulou et al. 2013). For its viability in food, it is necessary that they provide pleasant sensorial aspects in the product, viability during processing and product stability during storage (Mattila-Sandholm et al. 2002).

The main bacteria of interest with probiotic potential, especially for fermented dairy products, belong to the genera Bifidobacterium and Lactobacillus (Samaržija et al. 2009). Among these, L. casei stands out for having probiotic properties and technological characteristics important for its application in foods, adapting easily to stressful conditions in the food and being applied mainly to dairy products, such as yoghurts and fermented dairy beverage (Nezhad et al. 2015).

The elaboration of functional foods, using the combination of water-soluble oat extract (SOE), whey and probiotic L. casei, can be considered an option that adds nutritional value and, at the same time, brings benefits to consumer health, maybe being an alternative to dairy derivatives. In SOE it is possible to find dietary fibers, being it composed of 55% soluble fiber (Fuller et al. 2016). El Khoury et al. (2012) analyzed the presence of β-glucan in oats and found 3–8 g (g per 100 g dry weight), being 82% of them water-soluble β-glucans. This provides consumers with increased dietary fiber consumption, thus improving health.

In addition, SOE can contain phenolic compounds and other soluble antioxidants such as ferulic acid, avenanthramides (AVAs) and several other phenolic acids (Rasane et al., 2015). The total free phenolic acid esters in oats are found at about 8.7 mg/kg, whereas soluble phenolic acid esters account for 20.6 mg/kg (Peterson, 2001). All of these compounds provide a vast range of health benefits.

According to Doehlert et al. (2010), the addition of oats to the product may enhance the functional aspect of the probiotic fermented oat dairy beverage, as it would increase the content of mono and polyunsaturated long chain fatty acids.

To our knowledge, there are no studies on dairy beverage with the addition of SOE, but we are convinced that the obtained extract will provide beneficial effects associated with soluble fraction oat, when consuming the dairy beverage.

Thus, the objective of the present study was to develop fermented dairy beverage containing SOE, evaluating the viability of the probiotic culture, the fatty acid profile, phenolic compounds content and sensory characteristics, during storage.

Materials and methods

Preparation of water-soluble oat extract (SOE)

To obtain the SOE, 750 mL of distilled water should be used per 500 g of oat bran (Nestlé®). This mixture was held for 1 h and then crushed in a food processor for 2 min. After straining with a fine mesh sieve, the aqueous extract was kept under refrigeration to be used in the formulation of the milk beverage.

Microbial cultures

The cultures Streptococcus thermophilus and Lactobacillus delbrueckii bulgaricus (Chr. Hansen®) and probiotic L. casei LAFTI L26 (Globalfood) used in this study were obtained commercially. The probiotic culture originated from infantile intestinal tract, and its probiotic properties were evaluated by Paturi et al. (2008).

Dairy beverage formulation

Two dairy beverage formulations containing soluble oat extract (BA and BAC) were prepared using as base formulation 40% milk (v/v) (BRF®), 30% whey (v/v) (BRF®) and 30% SOE (v/v), according to Funck et al. (2019). Formulation BA contained only starter cultures, while formulation BAC contained starter cultures and probiotic culture L. casei LAFTI L26. For control, two other formulations (B and BC) were prepared without the addition of SOE, using 51% milk (v/v) and 49% whey (v/v), according to Fiorentini et al. (2011). Formulation B contained only starter cultures, while BC contained starter culture and L. casei LAFTI L26 (BC).

In both base formulations, 10% sucrose (m/v) and 0.01% starter cultures (m/v) were added. BAC and BC formulations also had 0.01% (m/v) probiotic culture L. casei LAFTI L26 (aiming at an initial concentration of ∼ 7.0 Log CFU.g⁻¹).

After the preparation, they were thermally treated (90 °C) for 5 min, then cooled to 42 °C, added with starter culture and then cooled to 37 °C, so that the probiotic could be added. Thereafter, the formulations were raised during fermentation, until pH values ranged from 4.5 to 4.7. Then, the clot was broken and potted. The dairy beverages were stored at refrigeration temperature (4 °C ± 0.5 °C) for 21 days.

Microbiological analyses

The viability of Lactobacillus casei and monitored starter cultures was determined on days 0, 7, 14 and 21, by diluting 25 mL of the different formulations of prepared dairy beverages in 225 mL of peptone water 0.1% (PW) (Acumedia®). From this, decimal dilutions were made and plated on MRS agar (Man, Rogosa and Sharpe) (Acumedia®) for the count of starter cultures present in formulations BA and B (without probiotic). For the probiotic L. casei, MRS agar, supplemented with 0.15% bovine bile (Sigma-Aldrich, USA) was used, since in these concentrations bile salts inhibit starter cultures (unpublished data). The plates were incubated for 48 h at 37 °C, under anaerobic conditions.

Considering the aspect of product safety, microbiological analyses of quantification of thermotolerant coliforms (45 °C) and the presence of Salmonella spp. (APHA 2001) were carried out in dairy beverages, during the storage period of 21 days, according to the parameters required by RDC nº 12/2001 (Brasil 2001).

Analysis of bioactive compounds and potential antioxidants

Ethanolic extracts were made in order to determine the bioactive composition and antioxidant potential of dairy beverages (BA; BAC; B; BC). In addition, the SOE that was incorporated into the formulation of dairy beverages was also analyzed. The ethanolic extract was made following the methodology of Chen et al. (2018), with adaptations. After the addition of the solvent, they were held in an ultrasonic bath (Quimis) (48 A) for 15 min, centrifuged for 5,200 g for 10 min, filtered on cotton and stored in ultra-freezer ( − 80 °C) (Indrel/IULT 335D) until analyzes were performed. Bioactive compounds and potential antioxidants were determined only at the beginning and at the end of the experiment (0 and 21 days).

The quantification of the total phenolic compounds was performed using the methodology of Singleton and Rossi (1965), with adaptations. For the reaction, Folin-Ciocalteu and 20% NaCO₃ (Vetec Química) were used, with a reaction of 2 h and reading at 765 nm in a UV–VIS spectrophotometer (model JENWAY 6705). A calibration curve with gallic acid (Sigma-Aldrich, USA) as standard (5–50 mg L⁻¹) was used for the quantification, and the results were expressed in milligrams of gallic acid per gram of dry sample (mg EAG g⁻¹).

To determine the total flavonoids, the methodology used was that of Zhishen, Mengcheng and Jianming (1999). The reaction was carried out using AlCl₃ (Vetec Química) with a time of 40 min and reading at the length of 415 nm in the UV–VIS spectrophotometer. For quantification, a calibration curve was obtained using quercetin (Sigma-Aldrich, USA) as standard (1–10 mg L⁻¹). The results were expressed in milligrams equivalent to quercetin per gram of sample (mg EQ g⁻¹).

The sequestration of DPPH (2,2-diphenyl-1-picrylhydrazyl) (Sigma-Aldrich, USA) radical was determined using Brand-Williams, Cuvelier and Berset (1995). The ethanolic extract was mixed with a DPPH solution with known absorbance, and after 100 min of reaction, it was read at 517 nm in the spectrophotometer. As for the removal of ABTS (2,2′-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid)) (Sigma-Aldrich, USA), the radical was determined by the reaction of the extract with the ABTS solution, which was obtained with ABTS and potassium persulfate, resting for 16 h prior to analysis. The duration of the reaction was 6 min and the reading was performed at 734 nm in the spectrophotometer (Gülçin et al. 2010).

Calibration curves (1–50 mg L⁻¹) were used for all methods using Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid) (Sigma-Aldrich, USA) as the reference standard, and the results were expressed in millimoles of Trolox per gram of dry sample (mmol Trolox g⁻¹).

Determination of fatty acid profile

Lipids were extracted in triplicate from dairy beverage formulations with SOE and without SOE and probiotics and analyzed in 0 and 21 days, according to ISO method 14,156 (2001), with adaptations. Fatty acid methyl esters (FAMEs) were prepared by esterification according to ISO method 15,884 (2002). The fatty acid composition was determined using a QP2010 Ultra gas chromatograph coupled to a mass spectrometer (GC/MS) (Shimadzu, Tokyo, Japan). The CG was equipped with an OV-5 ms capillary column (30 mx 0.25 mm, 0.25 m, Agilent J&W DB-Wax, USA) with isothermal programming starting at 78 °C for 6.5 min, temperature ramp of 60 °C/min up to 180 °C for 13.44 min, new heating ramp of 35 °C/min up to 280 °C for 10.50 min, totaling 35 min of analysis. Helium was used as a carrier gas with a flow rate of 1 mL/min. A scanning rate of 0.3 s covering a range of masses of 40 to 450 m/z was applied for detection. Identification and quantification of fatty acids was performed by comparing the peak retention times of the standards (catalog # 05,632, 189–19; Sigma, Bellefonte, PA, USA) with the peaks produced by the samples after methylation. The quantitative composition of each fatty acid was calculated from the area of each peak and expressed as a percentage according to the official method Ce 1–62 (AOCS 2005). The classification of fatty acids, relative to the chain number of carbon atoms, was determined according to Ackman (2007).

Sensory analysis

The study was submitted to the Ethics Committee in Research with Human Beings, approved and registered in Plataforma Brasil, under CAAE (Certificado de Apresentação para Apreciação Ética) N^o 70551317.8.0000.5317.

Tests assessing acceptance and purchase intention were performed for the dairy beverage including fermented oat with starter culture and probiotic (Lactobacillus casei) (BAC). The acceptance test had a structured 9-point hedonic scale, ranging from (1) disliked very much to (9) liked very much, for each sensory attribute. Panel members evaluated the samples in terms of color, odor, flavor and overall appearance. For the purchase intention test, each sample was evaluated on a hedonic 5-point structured scale, ranging from (1) would never buy to (5) would always buy (ISO method 11,136, 2014).

Sensory tests were performed with 100 untrained evaluators. This step took place at the Sensory Analysis Laboratory of the Federal University of Pelotas (UFPel), in individual booths with white lighting.

Statistical analysis

The data were submitted to analysis of variance (ANOVA). In cases of significant difference, a T-test was applied for a qualitative treatment factor with two levels, Tukey for three or more levels and Dunnett's test for comparisons between formulation and control. Simple correlation analysis between phenolic compounds and flavonoids was done through the program Statistica, version 6.0 (Statsoft, USA).

Results and discussion

Microbiological analyses

According to the results, it was possible to verify that starter cultures used in the experiment remained viable in the fermented oat dairy beverage, during the storage period evaluated (counts above 7 log of viable cells per mL). No significant difference was verified for the treatment factors [formulations (BA and B) and time (0, 7, 14 and 21], indicating that the addition or not of oat extract and time did not influence the viability of the starter cultures.

The analysis of variance for counting probiotic bacteria in BAC and BC treatments showed that only time was significant (p = 0.0047), therefore the addition or not of oat extract does not affect the viability of the probiotic bacteria. It can be observed that the storage time allowed a development of the probiotic, as there was a significant difference between the initial time and the 21st day (Fig. 1).

Fig. 1.

Viability of Lactobacillus casei in dairy beverage with water-soluble oat extract (BAC) during the storage period (vertical bars indicate confidence interval at 95% probability)

It is considered that the application of probiotics in dairy products is a challenge, as they may lose their viability in the product during storage and during shelf life (Kareb and Aïder 2019). However, according to the results obtained, L. casei remained viable during the days in which its viability in the dairy beverage was analyzed, counts between 7 and 8 Log CFU mL⁻¹ was observed during the storage period.

For a food to be considered probiotic, a minimum of 6 Log CFU mL⁻¹ must be present in the product. This is to ensure that a sufficient number of cells are ingested to remain viable during gastrointestinal transit and have effect on the host. Concerning the case of the elaborated dairy beverage (BAC), the combination of oats (prebiotic) with L. casei (probiotic) may improve the functional properties of the product.

Regarding the analysis of pathogenic bacteria, as established by RDC nº 12/2001 (Brasil 2001), there was no presence of Salmonella spp., and it was not possible to count thermotolerant coliforms. Thus, the sample was in agreement with the recommendation found in legislation.

Bioactive compounds and potential antioxidants

The results observed in this study demonstrate that levels of bioactive compounds and antioxidant capacities increase between the beginning and the end of storage period. They also evince that the addition of SOE provides an increase of antioxidant capacity (Table 1). According to Cai et al. (2014), fermented products added with different cereals such as wheat, brown rice, oats and corn showed an increase in the contents of phenolic compounds and antioxidant properties (determined by DPPH radical sequestration methods and radical inhibition ABTS). Đorđević, Marinkovic and Dimitrijevic-Brankovic (2010) observed that the fermentation by Lactobacillus rhamnosus and Saccharomyces cerevisiae increased the total phenolic content and antioxidant activities. However, the use of the probiotic in this study (Lactobacillus casei) did not show the same effect as that observed by the authors (Table 1).

Table 1.

Bioactive compounds and potential antioxidants of dairy beverage with and without addition of water-soluble oat extract with starter culture (BA; B) and with L. casei (BAC; BC) (means ± standard deviation)

Analysis	Phenolic compounds (mg EAG g−1)	Flavonoids (mg EQ g−1)	DPPH (mmol Trolox g−1)	ABTS (mmol Trolox g−1)
Water-soluble oat extract	0.13 ± 0.03	0.10 ± 0.03	2.10 ± 0.35	5.01 ± 1.38
	without probiotic
B (B)*	0.06bA**	0.05bA	1.08bA	2.22bA
BA (B)	0.05aA	0.03aA	0.75aB	1.38bB
B (E)	0.08aA	0.07aA	1.63aA	3.70aA
BA (E)	0.06aB	0.05aA	0.82aB|	2.32aB
	with probiotic
BC (B)	0,05aA	0,04aA	0,54bA	1,25aA
BAC (B)	0,05aA	0,03aA	0,57aA	0,61aB
BC (E)	0,06aA	0,04aA	0,72aA	2,03bA
BAC (E)	0,05aA	0,04aA	0,62aA	0,74aB

BA Starter culture (without water-soluble oat extract); BAC: Starter culture and Lactobacillus casei (without water-soluble oat extract); B: Starter culture (with water-soluble oat extract); BC: Starter culture and Lactobacillus casei (with water-soluble oat extract)

^*(B): Beginning of the experiment; (E): End of experiment; **Equal lowercase letters between times of dairy beverage produced with or without water-soluble oat extract and equal capsules between dairy beverage produced with and without water-soluble oat extract at the same time do not differ among themselves by the test t considering 5% of significance

According to the simple correlation analysis between variables, it was possible to observe a high level of correlation between phenolic compounds and flavonoids (R²: 0,91) and antioxidant potential by ABTS (R²: 0,92), as well as flavonoids and ABTS (R²: 0,84). In addition to the results of the correlation analysis, the relatively higher data among the methods tested for antioxidant potential (higher for ABTS) show that the DPPH radical sequestration method is not the most suitable for this matrix. The antioxidant capacity of extracts of oats and other grains can be correlated with the presence of phenolic compounds (Adom and Liu 2002).

Considering the two methods for determination of antioxidant potential, it was observed that the best method was by ABTS, both in correlation with phenolic compounds and in the results themselves. The difference between these methods for determining antioxidant activity is widely discussed in the literature and a specific method is always found for each analyzed matrix, due to the different types of radicals and the different action sites (Frankel and Meyer 2000), as observed in this study.

Fatty acid profile

Analysis of variance of the fatty acids showed interaction between the treatment factors [formulations (BAC, BA, BC and B) and time (initial time and after 21 days) for C10:0, C12:0, C14:0, C18:1n9 and C18:0 (Table 2). Only the main effect of the formulation was found for C16:0 and C18:2n6, indicating that the time does not influence the concentration of these fatty acids (Table 3).

Table 2.

Effect of interaction between treatment factors on the fatty acid profile in different dairy beverage formulations over the refrigerated storage time

Formulation	Initial time
	C10:0	C12:0	C:14:0	C18:1n9	C18:0
BAC	1.08 ± 0.53 * α € A	1.60 ± 0.75 * β € A	7.98 ± 3.47 * β € B	24.85 ± 0.57 ns α € A	13.86 ± 2.00 ns β ¥ B
BA	3.26 ± 0.58 A	3.82 ± 0.01 A	14.74 ± 0.17 A	18.44 ± 4.12 A	14.16 ± 0.77 A
BC	2.12 ± 0.38 B	3.32 ± 0.53 B	15.23 ± 1.42 B	20.07 ± 3.60 A	18.16 ± 0.35 A
B	2.94 ± 0.22 A	4.47 ± 0.37 A	17.21 ± 0.41 A	19.97 ± 1.40 A	16.33 ± 0.24 A

Formulation	After 21 days of refrigerated storage at 4 °C
	C10:0	C12:0	C14:0	C18:1n9	C18:0
BAC	4.40 ± 2.93 ns α ¥ A	5.18 ± 2.58 ns α ¥ A	13.79 ± 0.32 ns β € A	20.47 ± 0.99 ns β ¥ B	19.19 ± 2.16 ns α ¥ A
BA	2.23 ± 0.78 A	3.69 ± 1.25 A	15.57 ± 3.19 A	15.63 ± 4.37 A	16.47 ± 1.28 A
BC	3.22 ± 0.09 A	4.95 ± 0.04 A	18.52 ± 0.82 A	17.33 ± 1.67 A	16.59 ± 0.01 B
B	3.06 ± 0.32 A	4.65 ± 0.50 A	17.75 ± 0.89 A	16.45 ± 4.01 A	16.41 ± 0.75 A

BAC = dairy beverage with water-soluble oat extract and probiotic bacteria

BA = dairy beverage with water-soluble oat extract and no probiotic bacteria

BC = dairy beverage without water-soluble oat extract and with probiotic bacteria

B = dairy beverage without water-soluble oat extract and without probiotic bacteria

* e ns represent a significant and non-significant difference comparing BAC with BA by Dunnett's test (p ≤ 0.05)

β e α represent a significant and non-significant difference comparing BAC with BC by Dunnett’s test (p ≤ 0.05)

€ e ¥ represent a significant and non-significant difference comparing BAC with B by Dunnett’s test (p ≤ 0.05)

Different upper case letters on the same line indicate significant difference by the T test (p ≤ 0.05) comparing the initial and final time, fixing the formulation

Table 3.

Main effect of fatty acids in different dairy beverage formulations over the refrigerated storage time

Formulation	C16:0	C18:2n6
BAC	29.68 ± 5.54 * β €	14.11 ± 10.77 ns β €
BA	35.73 ± 1.46	10.95 ± 3.11
BC	36.84 ± 0.71	3.40 ± 1.11
B	35.98 ± 0.25	4.42 ± 2.49

BAC = dairy beverage with water-soluble oat extract and probiotic bacteria

BA = dairy beverage with water-soluble oat extract and no probiotic bacteria

BC = dairy beverage without water-soluble oat extract and with probiotic bacteria

B = dairy beverage without water-soluble oat extract and without probiotic bacteria

* e ns represent a significant and non-significant difference comparing BAC with BA by Dunnett's test (p ≤ 0.05)

β e α represent a significant and non-significant difference comparing BAC with BC by Dunnett’s test (p ≤ 0.05)

€ e ¥ represent a significant and non-significant difference comparing BAC with B by Dunnett’s test (p ≤ 0.05)

Saturated fatty acids: capric (C10:0), lauric (C12:0), myristic (C14:0), palmitic (C16:0) and stearic acid (C18:0) were detected for all formulations, as well the unsaturated fatty acids: linoleic (C18:2n6) and oleic (C18:1n9). It was observed that saturated fatty acids were the major ones varying the percentage concentration of 67.28 to 79.52%, whereas the unsaturated ones ranged from 21.35 to 32.72%. For all experiments, the majority of saturated fatty acid was palmitic (C16:0), while most of the unsaturated fatty acid was oleic (C18:1n9). The oleic acid is important for its modulation of inflammatory response, protection against heart and liver damage and antioxidant activity), among other benefits (Lopez-Huertas 2010; Romana-Souza et al. 2020).

The comparison between BAC and BA allows isolated analysis of the effect of the addition of probiotic bacteria in the fatty acid profile. Differences were observed in the fatty acids C10:0, C12:0 and C14:0 at the initial time. However, during the 21 days of storage, these differences were not verified. A comparison between BAC and BC allows isolated analysis of the influence of SOE addition on the fatty acid profile. It can be observed that the formulation without addition of SOE presented higher concentration of the saturated fatty acids C12:0, C14:0 and C18:0 at the initial time. In 21 days, difference can be observed in C14:0 and in C18:1n9.

The comparison between BAC and B allows verification of the synergic effect of the addition of oats and probiotic bacteria in the profile of fatty acids. It can be demonstrated that there was difference for the saturated fatty acids C10:0, C12:0 and C14:0. Concerning these, higher concentrations occurred in the treatment without addition of oats and probiotic bacteria regarding the initial time. Unsaturated fatty oleic acid (C18:1n9) was higher for the formulation containing oats and probiotic bacteria at the initial time and, at 21 days of storage, only C14:0 presented a difference between the treatments, continuing higher for the formulation without addition of SOE and probiotic bacteria.

Comparisons over time for each formulation indicated for BAC that there was an increase in C14:0 and C18:0 and decrease in C18:1n9. The other fatty acids remained with their constant concentrations. BA and B formulations maintained the concentrations of the constant fatty acids. The BC formulation showed increase in C10:0, C12:0 and C14:0 fatty acids and reduction of C18:0.

The main effect for the formulation performed for C16:0 showed that BAC presented lower concentrations compared to the other formulations. C18:2n6, however, presented higher concentrations for BAC and BA. This indicates that the addition of SOE increasesthe concentration of this fatty acid, which is positively related tothe prevention of modulate and/or inflammatory immune responses (Kim et al., 2016). According to Doehlert et al. (2010), oat grains contain much more polar lipid concentration than other plant tissues.

Sensory analysis

The sensory evaluation of the fermented oat dairy beverage with Lactobacillus casei (BAC) was highly appreciated by consumers, with an equal acceptance rate of 84.4%, thus presenting market potential. The attributes evaluated in the product were color, odor, texture and flavor, and the average scores obtained for each attribute were 7.4, 7.36, 8.13 and 7.89, respectively (Fig. 2).

Fig. 2.

Acceptance test of fermented oat dairy beverage with Lactobacillus casei by untrained evaluators

Regarding the intention to buy the product, it was observed that 47 and 34% of consumers certainly would buy and would possibly buy respectively, while 14% declared indifference and only 5% would not be interested in buying the developed product. The probiotic fermented dairy beverage added with SOE was presented as a viable alternative for the use of this cereal, in a functional product with high nutritional value and good acceptance among potential consumers.

Conclusion

The addition of water-soluble oat extract (SOE) in the BAC formulation to the fermented dairy beverage did not interfere in the viability of L. casei, which remained viable (counts above 7 Log CFU/mL) during 21 days of storage of the product.

The addition provided differences in bioactive compounds and potential antioxidants during shelf life. The addition of SOE in the formulation contributes to a significant increase in linoleic acid (C18:2n6). Finally, the sensory analysis assessing acceptance and purchase intention presented quite satisfactory results, indicating a good market potential.

The combination of SOE along with probiotic L. casei is technologically feasible in the production of novel probiotic fermented dairy beverage. It improves the functional properties of the product and offers potential health benefits to the consumer.

Additional studies should be made to evaluate the composition and functional properties of water-soluble oat extract.

Author contributions

Author Vera Maria Klajn: Conceptualization, Methodology, Data curation and Writing- Original draft preparation; Camila Waschburger Ames: Methodology, Data curation and Writing; Kamila Furtado da Cunha: Methodology, Data curation, and Writing; Alexandre Lorini: Methodology and Data curation; Helen Cristina dos Santos Hackbart: Methodology and Data curation; Pedro José Sanches Filho: Methodology and Data curation; Claudio Eduardo dos Santos Cruxen: Methodology, Data curation and Writing- Original draft preparation; Ângela Maria Fiorentini: Conceptualization, Methodology, Data curation and Writing- Original draft preparation.

Funding

Not applicable for that section.

Code availability

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Data availability

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Compliance with ethical standards

Conflicts of interest

The authors declare that they have no conflict of interest.

Consent to participate

All authors read and approved the final manuscript.

Consent for publication

We agree with the publication of the manuscript including its tables and figures.

Ethics approval

Ethics Committee in Research with Human—approved and registered in Plataforma Brasil—CAAE (Certificado de Apresentação para Apreciação Ética), N^o 70551317.8.0000.5317.