Synbiotic yoghurt with walnut and cereal brittle added as a next‐generation bioactive compound: Development and characteristics

Abstract The article presents a technology developed for the production of synbiotic Yoghurt with new bioactive filler based on natural components. The Yoghurt has prebiotic and sorption properties. A higher consumer appeal of the product developed has been substantiated; its characteristics compared with the Yoghurt of traditional production technology have been presented. The brittle, containing peeled walnuts, as well as barley, wheat, rye, oatmeal and buckwheat flakes, sugar, and water, was used as a filler. Optimum time and temperature regimes of boiling caramel mixtures and brewing raw walnut–cereal mass in the brittle have been selected. The formulation developed enables increasing the nutritional and biological values of the finished product. The research studies of the finished product involved an analysis of organoleptic, physicochemical, and microbiological points. When performing the tasks, the approved regulatory and technical documentation (GOST) was applied. Each measurement was carried out in triplicate. The physicochemical characteristics of the samples developed were compared with the requirements for the quality of fermented milk products. The nutritional and biological values were calculated. The increase in consumer properties, and nutritional and biological values of the finished dairy product was scientifically substantiated and experimentally confirmed.


| INTRODUC TI ON
For millennia, microbes have been used in the production of food and beverages; the technology involves the fermentation process.
In recent years, the attention of scientists has been attracted by identifying fundamental mechanisms and influence patterns of food and beverages on the human body, and as a consequence, the options of their use in the food industry for preventive and therapeutic purposes. As a result, the world community has got a new term "probiotics." Lactic acid bacteria (LAB) are normal microflora in the intestines of mammals (Markowiak & Slizewska, 2018;Young, 1998).
They play an important role in the process of vital activity and act as an immunomodulator. The LAB are widely used for prevention and treatment of gastrointestinal diseases, as well as for improvement of digestion and more complete absorption of nutrients. Probiotic microorganisms include lactic acid bacteria such as Lactobacillus acidophilus, L. bulgaricus, L. casei, L. plantarum, and L. rhamnosus. These applied live bacteria promote the development of the immune response and distribution of the vaccine component in the body. Complexes of pathogenic and nonpathogenic food microbes are currently evaluated as candidates for oral vaccines. Intestinal microflora plays a crucial role in the metabolism of various nutrient substrates in the vital activity. There are numerous studies of pre-, pro-, and synbiotics, confirming clinical efficiency in maintaining the balance of the gastrointestinal microbiota to improve health (Nakagawa, Yabuuchi, Yasokawa, & Nagashima, 2005;Quigley, 2019;Singh, Amdekar, Yadav, Mishra, & Jain, 2011;Sukhikh, Krumlikov, Evsukova, & Asyakina, 2017;Vyas & Ranganathan, 2012). Prebiotics are known to be food components that are not digested and absorbed in the upper gastrointestinal tract, since gastric enzymes cannot act on them; but they are fermented by the microflora of the human large intestine and stimulate its growth and vital activity. They reach the colon intact and are selectively fermented to have a beneficial effect. Probiotics are live cultures of microorganisms and substances of microbial and other origin. Synbiotics are combined bacterial preparations containing prebiotics and probiotics and belong to the innovation group of biologics (Mohanty, Mishra, Mohapatra, & Sahu, 2018;Roberfroid, 2000;de Vrese & Schrezenmeir, 2008).
A bioactive compound is a simple substance that has a biological activity associated with its ability to modulate one or more metabolic processes, which leads to improved health (Angiolillo, Nobile, & Conte, 2015;Watson & Preedy, 2015).
One of the most important tasks in addressing the food safety and nutrition issues and achieving the goals of sustainable development is the elimination of all forms of malnutrition (FAO et al., 2017). In 2016, the decade of the UN action on nutrition began (2016)(2017)(2018)(2019)(2020)(2021)(2022)(2023)(2024)(2025).
In Russia, in the framework of the Order "On basic principles of state policy in the field of healthy nutrition of the population of the Russian Federation for the period of up to 2020," there were some improvements noted in the area of nutrition of the population due to changes in the structure of food consumption, that is, increasing the share of specialized meat and dairy products (The order of the Government of the Russian Federation dated 25.10.10). So, obvious is the relevance of expanding the range of functional fermented milk products that improve digestion, quickly eliminate hunger, and are a source of micro-and macronutrients (McAuliffe, Kilcawley, & Stefanovic, 2019;Slozhenkina, Druker, Kryuchkova, & Zlobina, 2018;Slozhenkina, Serova, Vodolazkova, & Zlobina, 2017). Among the variety of dairy products, Yoghurts can be considered the most common and attractive for the consumer; their advantages, in particular, include light texture, pleasant organoleptic characteristics, and various fillers and functional ingredients that are able to be added to the production technology and increase the biological and nu- Leaf Extract (Lestari, Nissa, Afifah, Anjani, & Rustanti, 2017), and Purple Sweet Potato (Tari, Handayani, & Hartati, 2018) are known to be used as fillers for the production of synbiotic yoghurt.
The authors proposed a recipe and developed a technology for the production of a new synbiotic Yoghurt using a nontraditional filler, that is, brittle of walnut and five cereal flakes (barley, wheat, rye, oats, and buckwheat) as a prebiotic component and plant sorbent ( Figure 1).

Highlights
• A higher consumer appeal of the product developed has been substantiated; its characteristics compared with the Yoghurt of traditional production technology have been presented.
F I G U R E 1 Raw materials for enriched product: (a) walnuts; (b) cereal flakes; (c) sugar; (d) water; and (e) milk 2 | MATERIAL S AND ME THODS

| The samples of raw materials and the production technology
The set yoghurt was produced in accordance with the traditional technological scheme (Tamime & Robinson, 2007) that includes the following steps: delivery of raw materials; filtering, cooling, and storage; heating, standardization, and homogenization; pasteurization and recooling; fermentation; filling, packaging, and labeling; souring and recooling; and storage ( Figure 2 and Table 1).
At the fermentation stage, dry bacterial starter culture was used to produce dairy products based on Lactobacillus bulgaricus, Lactobacillus casei, and Streptococcus thermophilus (LbS 22.11 series, "AiBi," OOO "Green Lines," Russia). AiBi direct application starters are highly concentrated lyophilized cultures containing a mixture of precisely defined strains that provide effective and reliable development of the acidity, good texture of the product, precisely defined production process, and exactly determined time of ripening. They are phage-alternative and phage-resistant for a long time.
Brittle was chosen as bioactive filler with prebiotic and adsorbing properties; there was a developed formulation that included peeled walnuts, flakes of wheat, rye, oat, barley and buckwheat, sugar, and water. All brittle samples were produced according to one recipe, except for Test I sample added with citric acid (5 g per 100 g of the mixture). Three brittle samples were developed, that is, Control with low melting point; Test I with citric acid, and Test II with high melting point.
F I G U R E 2 Technological scheme for the product enriched (thermostatic method) The basic scheme of the brittle production included the operations of raw material preparation, syrup boiling, walnut-cereal mass brewing, forming, cooling, and storage ( Figure 2 and Table 1).
Optimum time and temperature conditions for boiling caramel mixtures and brewing raw walnut-cereal masses in caramel were determined using a single-block logic programmable controller OVEN The experimental study to establish the optimum temperature and time of melting the caramel mixture was carried out as follows. The sugar syrup was stirred and boiled to a moisture content of 4%-6% at a temperature of 100-180°C (Table 2).
Then, premixed walnuts and cereals were poured into the syrup and mixed. The walnut-cereal mass was molded and cooled to 20°C. In the metal container, there was a temperature sensor preinstalled and completely immersed in the area of the caramel mixture during the experiment. The sensor was connected to a monoblock controller with discrete and analogue inputs/ outputs on board for the OVEN PLK 150 small systems automation; the temperature and time regimes were recorded continuously throughout all the preparation stages. The controller was programmed by the professional programming system CODESYS v.2. This program helped output the information to a computer screen; all processes were presented in a temperature-time curve (Figure 3a-c).

| Analysis of the finished product characteristics
The research studies of the finished product involved an analysis of organoleptic, physicochemical, and microbiological points.
When performing the tasks, the approved regulatory and technical documentation (GOST) was applied. Each measurement was carried out in triplicate. The physicochemical characteristics of the samples developed were compared with the requirements for the quality of fermented milk products.
Technical regulations of the Customs Union "On safety of milk and dairy products" (TR TS 033/2013) and GOST 31981-2013 "Yoghurts.

| The calculation of the nutritional and biological values
The nutritional value (NV) was evaluated in accordance with the following formula: where P is the percentage of protein, %; F is the percentage of fat, %; C is the percentage of carbohydrates, %.

NV (kcal)
100 g = 4 ⋅ P + 9 ⋅ F + 4 ⋅ C The amino acid score (AAS) was calculated as follows: The coefficient of amino acid score difference (CAAS) was calculated by the following formula: where C i is the excess of amino acid score, %; C min is the minimum score of essential amino acids of evaluated protein relative to the physiolog-  Abbreviation: ns, not significant at p > 0.05 compared with data on the Control sample. ***p < .001. *p < .05. **p < .01.
F I G U R E 4 Profilograms of the samples: (a) brittle; (b) finished product n is the number of essential amino acids.
The biological value (BV) was calculated by the following formula: To assess the balance of essential amino acids with respect to the reference protein, the utility K i coefficient was calculated.
where AS i is the amino acid score of the i-indispensable amino acid in the product; AS min is the amino acid score of the first limiting amino acid in this product.
The utility coefficient of the i-indispensable amino acid (A i ) was used to calculate the utility coefficient of the amino acid composition (U), which was a numerical characteristic that reflected the balance of essential amino acids with respect to the standard (A i st):

| Statistical analysis
The experimental data were analyzed by the Statistica 10.0 package using conventional techniques. The threshold of 0.05 was considered a minimum threshold of the significance of differences

| Comparative quality evaluation of the brittle samples
The Control brittle sample was made at low melting point of the caramel mass (up to 127°C); the moisture content in the finished Abbreviations: AAS, an amino acid score; BV, a biological value; CAAS, a coefficient of amino acid score difference; K i , an utility coefficient; U, an utility coefficient of the amino acid composition.
product exceeded the similar value in the Test ones by 4.99% (p < .01) and 2.97% (p < .05), respectively. The Control sample was inferior to the Test ones (Table 3). So, the consistency of the Control sample was too short-brittle due to the insufficient caramelization degree (Figure 3d). The higher moisture content in the Control sample led to a lower content of macronutrients. So, the protein content was lower by 0.13 (p < .05) and 0.08% (p < .05); fat content  (Table 2 and Figures 3 and 4).

| Comparative quality evaluation the of finished product samples
To evaluate the quality of the finished product, a brittle Yoghurt sample (brittle was precrushed and mixed with Yoghurt) was compared with the Yoghurt sample produced according to conventional technology (Tamime & Robinson, 2007).
Comparative analysis of the Control sample and the enriched one is given in Table 4 As the evaluation showed (Table 6), the formation of lactic acid microorganisms was different in yoghurt samples enriched with bioactive filler (Test) and not enriched (Control). The brittle in Yoghurt influenced the growth and reproduction of lactic microflora.
In the industrial Yoghurt production according to the technology developed, the finished product was proposed to be packed in twosection plastic cups. Yoghurt and filler should be mixed before eating by the consumer.

| CON CLUS IONS
The technology was developed for the production of a new synbiotic Yoghurt with a plant filler in form of brittle with prebiotic and sorption properties. The brittle formulation was developed; in the course of laboratory studies using specialized hardware support, the temperature and time regimes of its production were optimized.
The increase in consumer properties, and nutritional and biological values of the finished dairy product was scientifically substantiated and experimentally confirmed.
F I G U R E 5 Amino acid composition of the samples in comparison with the reference protein (FAO/WHO), mg per 1 g of protein

ACK N OWLED G M ENTS
The authors are grateful to the Ministry of Science and Higher Education of the Russian Federation for the financial support in the implementation of this research according to the state assignment of NIIMMP.

CO N FLI C T O F I NTE R E S T
The authors declare that they do not have any conflict of interest.

E TH I C A L A PPROVA L
This study does not involve any human or animal testing.

I N FO R M E D CO N S E NT
Written informed consent was obtained from all study participants.