Production of probiotic ice cream with improved functional properties

This study aimed to use milk fermented with dietary fibre (wheat fibre and inulin) and cultures (yoghurt cultures, Lacticaseibacillus rhamnosus, Shouchella clausii and Weizmannia coagulans) in ice cream production. Besides, it was also aimed to use spore-forming probiotics in the production of ice cream, which attracts attention with their resistance to harsh conditions. In order to evaluate the quality characteristics of the produced ice cream samples, viable cell and spore numbers, sensory, physical, chemical, thermal properties and caloric values were examined. For the ice cream production, milk samples were prepared with the addition of 1.5% (w/w) dietary fibre and 5% (w/w) culture and fermented until 4.6-4.7 pH (mix 1). Also, mixtures prepared using milk, cream, milk powder, sugar, stabilizer and emulsifier were matured at 4 °C for 24 hours (mix 2). 30% (w/w) mix 1 and 70% (w/w) mix 2 were used to prepare the final mix (100%). For 90 days, inulin and S. clausii added ice cream samples showed the highest viability, while L. bulgaricus in fibreless and wheat fibre-added yoghurt ice cream samples showed the lowest viability. L. bulgaricus was the culture that suffered the most viable cell loss. On the other hand, L. rhamnosus showed good growth in fermented milk and ice cream samples. However, wheat fibre also stimulated this culture, allowing it to show high viability for 90 days at -25 °C. It has been observed that L. rhamnosus is a more suitable culture for freezing medium than L. bulgaricus. It was determined that S. clausii and W. coagulans were found in both vegetative and spore forms in ice cream samples. S. clausii was slightly higher than W. coagulans in terms of viable cell count in ice cream samples. It is important to optimally adjust the initial amount of culture used in the production of yoghurt ice cream and probiotic ice cream. In cases where it is more or less, unwanted live culture numbers can be obtained during storage. In some cases, a high initial amount can have the opposite effect and cause a rapid decrease in the number of ice creams during storage. Considering all samples, at least 6.72 log viable cells were found in the ice cream samples at the end of 90 days. It can be said that the initial viable cell counts are at a suitable level to provide the desired bacterial counts for 90 days. In sensory evaluations, ice cream samples received moderate (5 out of 9) and close to medium scores in terms of elongation in the spoon, degree of sweetness and melting time in the mouth parameters. When the sweetness scores of all samples (5.00-5.50) were examined, it was understood that the appropriate sweetness was achieved. In the ice cream samples with fermented milk, the sour taste was not felt very much in terms of sensory. The acidity of ice cream samples was slightly lower than the general acidity values of yoghurt and probiotic ice cream samples. In this way, low sourness scores were obtained. Acidic sour taste can suppress the sugar taste in the yoghurt ice cream and the probiotic ice cream. It is seen that the sweetness of the products is neither too much nor too little, at the most favourable degree by the panellists. The fact that the frosted structure scores are below 2 out of 9 indicates that the ratio of stabilizer and emulsifier, processing and storage temperatures were adjusted appropriately during the preparation of the mixes. Ice cream samples had colour and appearance scores in the range of 7.81-8.22 out of 9. There was no difference between the samples in terms of this parameter. Since no colouring components were used in the ice cream samples, they all had the same colour and appearance sensory. This shows that the parameters of structure and consistency, taste & smell and general acceptability were evaluated in a way that is not related to colour and appearance. The samples with the highest structure and consistency scores were the fibre-free ice cream containing S. clausii and the ice cream sample containing W. coagulans and inulin. These samples got 7.67 and 7.85 points out of 9, respectively. Ice cream with inulin and L. rhamnosus was the most liked sample in terms of both taste & smell and general appreciation. Yoghurt ice cream sample with wheat fibre added was the least liked sample in terms of these two parameters. Nevertheless, this sample has scored in the satisfactory-good range with 6.44 taste & smell and 6.78 general appreciation points. All of the samples were appreciated above the average. The samples with the highest structure and consistency scores were the fibre-free ice cream sample containing S. clausii and the ice cream sample containing W. coagulans and inulin. They got 7.67 and 7.85 points out of 9, respectively. The most appreciated sample in terms of taste & smell scores is the ice cream samples containing L. rhamnosus and inulin with a score of 7.93 out of 9. In terms of general acceptability, with 7.52-7.81 points out of 9, the most liked samples were L. rhamnosus fibre-free and inulin ice creams, S. clausii fiber-free and wheat fibre ice creams, and W. coagulans wheat fibre and inulin ice creams. As long as legal limits are followed, it is possible to produce ice creams in many different types and compositions. In this respect, the product range is quite wide, but in order to ensure the sustainability of these products, some other features should be considered besides the number of cultures. The first of these is the sensory properties for the consumer, and then the properties such as viscosity, texture, freezing, and melting point for industrial production. In addition, physical properties such as melting time, L*, a*, b*, and whiteness index (WI) correlate with sensory quality; also, considering chemical properties such as pH and titration acidity can be useful for understanding and interpreting product quality. Viscosity increased from 1.08 Pa.s to 2.77 Pa.s with the addition of culture and dietary fibre. Overrun in ice cream samples was achieved naturally, and the 13.6-25.8% range values were obtained. Culture addition increased the overrun (%), while dietary fibre supplementation decreased it. Initial drip and complete melt times were recorded as 2029 s and 3130 s, respectively, on average during storage. While adding wheat fibre increased the first dripping time in yoghurt ice cream and probiotic ice cream samples, it showed different effects on complete melting times in ice cream samples containing different cultures. While inulin did not affect the first dripping time, it slightly shortened the time of complete dissolution. Average values of 73.33 L*, -1.51 a*, 6.49 b*, 72.51 WI, 12.65 YI, 1.61 ΔE were obtained in all samples during storage. During storage, the hardness values are on average 1.672 N at -10 °C and 0.419 N at 5 °C; adhesive strength values 0.418 N at -10 °C, 0.104 N at 5 °C; Adhesive strength values were measured as 2,196 mJ at -10 °C and 1,303 mJ at 5 °C. Although ice cream samples had low fat destabilization values in the 10.39-31.43% range, melting values that did not decrease the sensory quality were obtained. The acidity level in yoghurt ice cream and probiotic ice cream remained at levels that would not cause a sensory disturbance, with the average pH of 6.27 and 0.32% titration acidity values recorded during storage. All ice creams contain an average of 36.17% dry matter, 5.79% protein and 5.91% fat. There was no difference between the crystallization temperatures (Tc) of the samples; the average Tc was measured as -19.37 ºC. Glass transition temperatures (Tg) range from -31.73 ºC to -28.17 ºC. The approach of Tg to the storage xxv temperature of -25 °C is desirable in terms of maintaining stability during storage. Melting temperatures (Tm) are between -2.79 ºC and 1.88 ºC. While control ice cream had the highest Tm, Tm values decreased with addition of culture and dietary fibre. All ice creams have an average caloric value of 167 kcal/100 g. As a result, the desired number of viable cells was achieved in all yoghurt ice cream and probiotic ice creams, and low acidity values were obtained, thus, the desired sensory taste was achieved. In terms of general acceptability, all yoghurt ice cream and probiotic ice creams had the same or higher scores than the control sample, except for the yoghurt ice cream with wheat fibre added. Ice cream production with the addition of dietary fibre and fermented milk with a single probiotic culture can be preferred both economically and in terms of the balance of cell viability and sensorial quality. Production of yoghurt and probiotic ice cream without the use of extra flavouring ingredients can be an economical option. Providing the lowest desired number of viable cells with a single probiotic culture is also economically advantageous. Further studies can be conducted on the types and amounts of dietary fibre. More dietary fibre can be added to the mix for noticeable changes in physical properties. Fermentation of spore probiotics in milk medium and use in ice cream production increases the original value of this study. The fact that probiotics with spores create a pleasant aroma in ice cream adds value to the study. In this way, it is hoped that the study will lead to further academic and industrial studies. Probiotic ice cream production with dietary fibre and a single probiotic culture can be preferred in terms of sensory properties, cell viability and economic aspect.