UTILIZATION OF WHEY IN KEFIR PRODUCTION

ABSTRACT

In this research, properties of kefir produced from bovine milk including whey in different rates (10%, 20% and 30%) were investigated. In the research, four different kefir samples were manufactured with raw milk without whey (sample 1) and whey were added in rates of 10% (sample 2), 20% (sample 3) and 30% (sample 3) of total milk. According to the results, kefir samples produced with whey were acceptable and they had better results especially for phase separation and taste properties compared to the control sample 1.

АННОТАЦИЯ

В данном исследовании были изучены свойства кефира, полученного из молока крупного рогатого скота, включая сыворотку в различных дозах (10%, 20% и 30%). В исследовании были изготовлены четыре разных образца кефира с сырым молоком без сыворотки (1-й образец) и добавлено сыворотки в количестве 10% (2-й образец), 20% (3-й образец) и 30% (3-й образец) от общего количества молока. Согласно результатам, образцы кефира, полученные с сывороткой, были приемлемыми и имели лучшие результаты, особенно по разделению фаз и вкусовым свойствам, по сравнению с контрольным образцом 1.

Keywords: Kefir, raw whey, pH, milk, fermented product, nutritional.

Ключевые слова: Кефир, сырая сыворотка, pH, молоко, ферментированный продукт, питательный.

Introduction. Whey is a by-product obtained from cheese production and contains high levels of lactose as well as proteins, mineral substances, and small amounts of fat. In our country, whey is generally utilized by converting it into powder form or by using it in curd cheese production. However, factors such as the difficulty of installing drying equipment and its high cost, the inadequacy of existing facilities, and transportation problems arising from the small-scale and dispersed structure of cheese-producing dairies cause a significant portion of whey to be discharged into the sewage system as wastewater. Eliminating these negative effects may be possible by utilizing whey, which is obtained as a by-product of cheese production at approximately ~2 million tons annually in our country, through various methods. Therefore, in this study, the usability of whey in the production of kefir, an important fermented product, was investigated. The main objectives of the study were determined as the recovery of nutrients present in whey, the transformation of kefir into a more functional product, and the improvement of production yield [1-2].

Material and methods. In the study, raw cow’s milk, kefir grains, and whey obtained from White Cheese production.

Raw milk → Separation (50±1°C) → Fat standardization (1–1.2% fat content) →A Control; B sample containing 10% whey; C sample containing 20% whey; D sample containing 30% whey →Heat treatment (90°C for 10 min) → Cooling (25±1°C) → Kefir grain addition (3%) →Incubation (25±1°C); until pH value of 4.5 → Draining → Packaging → Storage (4°C).

Raw milk → Separation (50±1°C) → Fat standardization (1–1.2% fat ratio) →A Control; B Sample containing 10% whey; C Sample containing 20% whey; D Sample containing 30% whey →Heat treatment (90°C 10 min) → Cooling (25±1°C) → Kefir Grain Addition (3%) →Incubation (25±1°C); until pH-value of 4.5 → Draining → Packaging → Storage (4°C) [2].

Milk (raw material) was diluted so that whey constituted 10%, 20%, and 30% of the total sample amount.

Raw milk diluted with whey in rates of 10%, 20%, and 30% of total milk. The titratable acidity values of kefir samples, total dry matter values (gravimetric method), fat contents (Gerber method), total ash contents, and total nitrogen values were determined. The pH values of the samples were measured using a digital pH meter with a combined electrode, and the viscosity values were measured using a HAAKE VT 181/VTR 24 viscometer with the MV II spindle. Viscosity measurements were performed at settings 1 and 4, and viscosity values were calculated by substituting into the following formula [2-3].

Viscosity (cP) = Measured value × Measurement setting × 3 (Spindle constant)

In addition, the serum separation values of the samples were determined according to, and sensory analyses were carried out with the participation of 10 panelists.

Results and discussion. The properties of the raw milk used as raw material in kefir production are presented in Table 1 together with their standard deviations.

Table 1.

Some properties of raw milk (n=2)

Table 2.

Some properties of whey (n=2)

When Table 1 is examined, it is seen that the fat, total dry matter, protein, and titratable acidity values of the raw milk used as raw material. Some characteristics of the whey used in kefir production are presented in Table 2 together with their standard deviations [4].

The properties of the rennet whey used in the study, as indicated in Table 2, show values close to the whey composition reported in various studies. However, the fat content of the whey used in this study is slightly higher than the whey fat contents (0.12–0.95%) reported in previous studies. This situation is considered to result from the parameters used by the plant from which the whey was obtained in White cheese production (such as coagulation temperature, curd cutting size, etc.), particularly from the use of whole milk in production [5].

Some chemical properties of the kefir samples are given in Table 3. The milk fat content in kefir should be at most 10%, while the total protein content should be at least 2.7%. However, no value to be complied with in terms of dry matter is specified in the notification. The standardization of the fat content to approximately 1% in order to produce low-calorie kefir and the addition of whey are the main reasons for the lower fat and dry matter contents. In the statistical analysis performed, the differences among samples in terms of fat, dry matter, ash, and protein contents were found to be significant [6].

Table 3.

Some properties of kefir samples (n=2)

The pH and titratable acidity values of the kefir samples are presented in Table 4.

Although very small increases (maximum 0.05) were observed in the pH values of the kefir samples during the storage period, no significant changes were generally detected (Table 4). It is known that in fermented dairy products such as yogurt, decreases in pH values are observed during storage due to the activity of lactic acid bacteria. However, a similar situation may not occur in kefir. In a manner similar to the samples examined within the scope of this study, another study reported that the pH values of kefir samples increased during storage [7]. The presence of yeasts in addition to lactic acid bacteria in the starter cultures and kefir grains used in kefir production may slow down acidity development; therefore, increases and very minor changes in pH values may be observed. In addition, it can be considered that the changes in dry matter and lactose levels caused by the use of whey, as well as buffering properties, are effective in the pH increases observed in the samples [8].

The titratable acidity values of the kefir samples showed a slight increase during the storage period. The production of kefir using starter cultures different from those of fermented products such as yogurt and ayran is the most important factor contributing to the slower development of acidity. Similar results have also been obtained in studies conducted on kefir. Among the samples, the highest titratable acidity value was observed in the control sample (Table 4). This situation also indicates that the addition of whey has an effect on acidity development [9].

In the statistical evaluation performed, the interaction between samples and storage days in terms of pH values and the difference among the titratable acidity values of the samples were found to be significant. At the same time, while the differences among storage days in terms of pH and titratable acidity values of the samples were found to be statistically significant, no interaction was found between samples and storage days [10].

Table 4.

The serum separation and viscosity values of the kefir samples are presented

As can be seen from the examination of Table 4, except for the 14th-day value of sample 2, the serum separation values of the whey-added samples were considerably lower than those of the control sample1. In this case, it can be stated that the increases in serum protein ratios in the whey-added samples and the interaction of these proteins with casein were effective in increasing the water-holding capacity of the samples. In addition, it may be considered that the increases in lactose content could be effective in terms of buoyancy. In a study conducted on kefir, it was also reported that the addition of whey protein concentrates positively affected the curd stability of kefir samples and reduced serum separation, similar to the results observed in our samples. During the storage period, serum separation increased in the samples. Sample 1 similar trend has also been reported in studies conducted on kefir [10-11].

The differences among the samples in terms of serum separation and viscosity values, as well as the differences among these values during the storage period, were found to be significant. In addition, the interaction between samples and storage days in terms of serum separation values was also found to be significant [11].

Conclusion. In this study, the usability of whey in the production of kefir, which is the most widely consumed fermented milk product in our country after yogurt and ayran, was investigated. The research results showed that kefir produced by adding whey to raw milk at different ratios (10%, 20%, and 30%) had acceptable physical and chemical properties. In addition, it was determined that the addition of whey reduced the serum separation value of kefir and positively affected the curd structure.

The sensory evaluation results also revealed that the whey-added samples were more preferred than the control sample. These findings demonstrated that whey can be used in kefir production.

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