Title : The effect of white mulberry addition on selected quality features of fermented milk
Abstract:
The aim of this study was to determine the effect of white mulberry addition on selected features of fermented milk. Fermented milks were prepared using a thermostatic method under laboratory conditions in the following variants: without white mulberry addition (control sample) and with 0.5%, 1.0%, 1.5%, 2.0%, and 2.5% white mulberry fruit. To obtain the fermented milks, a starter culture containing the following microorganisms: Streptococcus salivarius subsp. thermophilus, Lactobacillus delbruecki subsp. bulgaricus, was added to commercial UHT milk ("Łaciate" 3.2% of fat, "Mlekpol") as well as, depending on the variant, previously ground organic dried white mulberry fruit. All variants were obtained in three independent replication series. The average protein content in the tested fermented milks ranged from 3.67% to 4.04%. The lowest protein content was found in the fermented milk with 2.5% white mulberry addition and the highest in the control fermented milk. Whereas the average fat content in the fermented milks ranged from 3.03% for the milk with 2% white mulberry to 3.47% for the milk without addition of white mulberry (control). The addition of white mulberry increased the dry matter content in the fermented milks. The average pH values of the tested fermented milks ranged from 4.49 to 4.77. Fermented milk without added white mulberry had the highest average pH. With the increase in the content of added white mulberry, the pH value in fermented milks decreased. The addition of white mulberry lowered the pH value of fermented milks immediately after their receipt as well as after 10 days of storage in refrigerated conditions. White mulberry fruit also influenced the color parameters of the fermented milks. With the increase in the content of mulberry added to fermented milks, the brightness of fermented milks decreased and the color parameters a* (red-green) and b* (blue-yellow) increased. White mulberry fruit had a significant effect on the textural properties of the tested fermented milks. The highest hardness among the examined fermented milks was found in the milk with addition of 0.5% white mulberry (1.54 N), while the lowest hardness was found in the milk with 2.5% white mulberry addition (0.84 N). The lowest adhesiveness characterized the milk with 2.5% white mulberry added (3.53 mJ), while the highest adhesiveness was found in the control milk (7.39 mJ). Fermented milk containing 0.5% white mulberry fruit was characterized by the highest hardness and adhesiveness compared to the other milks containing white mulberry. As the white mulberry content increased, the hardness and adhesiveness of the fermented milks decreased. Based on statistical analysis, no significant effect of white mulberry addition on the appearance, aroma, or consistency of the fermented milks was found in the organoleptic evaluation, both immediately after production and after 10 days of storage. In terms of taste, the fermented milk with 1.5% white mulberry fruit was rated the best. The addition of white mulberry fruit allowed us to obtain a new, sensorially attractive fermented milk, which may have a positive effect on the human body, considering the bioactive properties of white mulberry.
Research financed by Ministry of Science and Higher Education, Poland, "Research network of life science universities for the development of the Polish dairy sector - research project" SUP-RIM
