Effects of Fermentation Vessels and Addition of Indigenous Plants on Microbial Growth, Physicochemical and Sensory Properties of Cultured Milk

BACKGROUND INFORMATION

Fermentation of dairy products is one of the oldest methods of food preservation. Fermented milk products are produced by the addition of selected bacteria to heat-treated milk, incubated at a suitable temperature and the pH lowered by the action of lactic acid bacteria (LAB) (Savaiano and Hutkins, 2021). Most of the communities in Kenya where milk is produced have historically consumed spontaneously fermented milk products. For instance, maziwa lala is a commonly consumed cultured milk product in many communities (Mwangi et al., 2023). A variety of sources, such as milk, milking equipment, and storage containers, can provide access for bacteria, yeast, and fungi to grow due to the nutritional content of milk. Naryhus and Abrahamsen (2023) reported that acid-producing microorganisms, especially lactic acid bacteria (LAB), can grow in a mixed population and take over the milk’s microbiota, hence suppressing pathogenic and spoilage organisms.

Based on the production technology, spontaneous fermentation, and back-slopping methods have been used. However, currently, starter cultures are used for large-scale production of fermented milk products, with an interest in the probiotic potential of the selected microorganisms (Galli et al., 2022). As a result of the probiotic effect, cultured milk has been recognized as one of the functional foods, which when consumed in adequate quantities, presents a health benefit to the host. This functional food is also packed with numerous nutrients, hence providing essential nutrients such as minerals and vitamins when consumed. Probiotics are microorganisms that remain viable throughout the processing stages, survive in the gastrointestinal tract, and offer health-promoting effects to humans who consume probiotic products. They maintain the normal intestinal microflora, ease inflammatory bowel disease (IBD), and protect against diarrhea (Kaur et al., 2022). Both spontaneous fermentation and back-slopping methods are facilitated by LAB, which utilizes lactose and produces lactic acid. LAB species commonly used include Lactococcus, Lactobacillus, Leuconostoc, and Pediococcus. The formation of lactic acid and modification of milk components leads to improved quality and increased bioavailability of nutrients (Bintsis and Papademas, 2022).

In many African communities, plants have been extensively used as nutritional additives, flavor enhancers, appetizers, and as medicine. Certain plants have been used to improve the flavor and increase the shelf life of milk and milk products. The type of plant used depends on the community, and the mode of application is unique to the people themselves. Some of the methods of application include applying the plant to the milk and the equipment used, either through cleaning, smoking with a burning end of chopped stick, or adding the burnt wood stick to the milk before fermentation (Shambel et al., 2021).

During the fermentation process of cultured milk, different vessels can be used, which include plastic containers, stainless steel containers, earthen pots, and calabashes. Research comparing traditional food fermentation vessels has shown that calabash is a lignocellulosic material that is more suitable for the traditional fermentation process of products intended to maximize their physicochemical, organoleptic, and microbiological properties (Kutaa, 2017). Calabash is used by some Kenyan communities in the manufacture of cultured milk. Among the different communities, cultured milk is in great demand for its taste, aroma, cultural values, and health benefits. Calabash helps in the formation of biofilm of LAB, hence limiting the development of pathogenic bacteria, and serving as an inoculum for the successive fermentation (Tchamba et al., 2021).

PROBLEM STATEMENT

According to Nduko et al., (2016), the fermentation process involved in the production of cultured milk depends on the microorganisms present in the environment, or from a sample of a previous batch of cultured milk as inoculum. Due to the uncontrolled nature of the processes, the final product may have inconsistent taste and quality. The process is inefficient due to the longer lag phase, and the safety of the product is not assured. Using selected starter cultures, there will be a reduction of contamination and the quality of the product will be assured. The increasing consciousness of the health benefits of cultured milk, urbanization, and immigration of people have led to increased demand for these foods. To meet the increased demand, there is a need for improvement in the quality and safety of traditional cultured milk, at the same time maintaining its unique taste, aroma, and characteristics. (Galli et al., 2022).

Studies have characterized the microorganisms present in some Kenyan spontaneously cultured milk (Lore et al., 2005; Mathara et al., 2004; Nieminen et al., 2013; Nyambane et al., 2014), but there is limited technology that has been developed to modernize the production of the traditional cultured milk using starter culture and in a controlled environment. The objective of most of the studies was to identify the microorganisms involved, which is necessary for the development of starter cultures. Modernization of the technologies can ensure consumer safety, provide consistently high-quality products, and gain broad acceptance among communities (Nduko et al., 2016). Current socio-economic changes can lead to the loss of the traditional technologies for the production of cultured milk. These technologies involve the use of indigenous plants to improve flavor and preserve the milk. Exploitation of these technologies can help to meet the consumer demands for probiotic natural food without preservatives (Kutaa, 2017). In some African countries, claims associate the best sensory characteristics with cultured milk fermented in calabashes. However, there is limited information on the effect of fermentation vessels on the microbial growth and physicochemical properties of cultured milk (Tchamba et al., 2021). Therefore, there is a need to investigate the effect of fermentation vessels and the addition of indigenous plants on microbial growth, the physicochemical and sensory properties of cultured milk.

OBJECTIVES

Main Objective

This study seeks to investigate the effects of fermentation vessels and the addition of indigenous plants on microbial growth, physicochemical and sensory properties of cultured milk,

Specific Objectives

1. To manufacture cultured milk using different fermentation vessels, with the addition of burnt wood sticks from indigenous plants.
2. To determine the physicochemical properties of the manufactured cultured milk samples.

• To determine the influence of fermentation vessels and the addition of burnt wood sticks on the growth of lactic acid bacteria.

1. To assess the sensory attributes of cultured milk obtained from different fermentation vessels, with the addition of burnt wood sticks.
2. To determine the shelf-life of the manufactured cultured milk samples.

METHODOLOGY

The production process of cultured milk among the Kikuyu community will be established through focus group discussion. The inquiries will be made on the type of fermentation containers used, how they are treated before fermentation, and a step-by-step production process. A laboratory-based production of cultured milk will be carried out, simulating the traditional processing method. Fermentation vessels will be prepared by the addition of burning embers of the selected indigenous plant (Nakavuma, 2012). Milk will be boiled to 85⁰C for 15 minutes, followed by rapid cooling to 25℃. A starter culture of mesophilic bacteria will be added at 0.2%. The milk will be allowed to ferment for 11-18 hours until a titatable acidity of 0.6% is attained. At the end, a field sample of traditionally cultured milk will be obtained. Both the field and laboratory fermentation samples will be analyzed for their microbial, physicochemical, and sensory properties.

REFERENCES

Narvhus, J. A., & Abrahamsen, R. K. (2023). Traditional and modern Nordic fermented milk products: A review. International Dairy Journal, 105641.

Savaiano, D. A., & Hutkins, R. W. (2021). Yogurt, cultured fermented milk, and health: A systematic review. Nutrition reviews, 79(5), 599-614.

Mwangi, A. W., Kunyanga, C. N., & Onyango, C. M. (2023). Development, nutritional and microbial evaluation of cultured bovine milk supplemented with baobab fruit pulp. CyTA-Journal of Food, 21(1), 198-208.

Galli, V., Venturi, M., Mari, E., Guerrini, S., & Granchi, L. (2022). Selection of yeast and lactic acid bacteria strains, isolated from spontaneous raw milk fermentation, for the production of a potential probiotic fermented milk. Fermentation, 8(8), 407.

Kaur, H., Kaur, G., & Ali, S. A. (2022). Dairy-based probiotic-fermented functional foods: An update on their health-promoting properties. Fermentation, 8(9), 425.

Bintsis, T., & Papademas, P. (2022). The evolution of fermented milks, from artisanal to industrial products: A critical review. Fermentation, 8(12), 679.

Shambel, Z., Kebede, E., Mengistu, M., & Lamboro, T. (2021). Identification and Evaluation of Preservative Plants on Traditionally Fermented Cow Milk. Current Research in Nutrition and Food Science Journal, 9(1), 329-337.

Nduko, J. M., Matofari, J. W., Nandi, Z. O., & Sichangi, M. B. (2016). Spontaneously fermented Kenyan milk products: A review of the current state and future perspectives.

Lore, T. A., Mbugua, S. K., & Wangoh, J. (2005). Enumeration and identification of microflora in suusac, a Kenyan traditional fermented camel milk product. LWT-Food Science and Technology, 38(2), 125-130.

Mathara, J. M., Schillinger, U., Kutima, P. M., Mbugua, S. K., & Holzapfel, W. H. (2004). Isolation, identification and characterisation of the dominant microorganisms of kule naoto: the Maasai traditional fermented milk in Kenya. International journal of food microbiology, 94(3), 269-278.

Nieminen, M. T., Novak-Frazer, L., Collins, R., Dawsey, S. P., Dawsey, S. M., Abnet, C. C., & Rautemaa, R. (2013). Alcohol and acetaldehyde in African fermented milk mursik—a possible etiologic factor for high incidence of esophageal cancer in western Kenya. Cancer epidemiology, biomarkers & prevention, 22(1), 69-75.

Nyambane, B., Thari, W. M., Wangoh, J., & Njage, P. M. (2014). Lactic acid bacteria and yeasts involved in the fermentation of amabere amaruranu, a Kenyan fermented milk. Food Science & Nutrition, 2(6), 692-699.

Kutaa, G. (2017). Microbial content and anti-microbial activity of Namibian traditionally fermented milk (Doctoral dissertation, Stellenbosch: Stellenbosch University).

Tchamba, N. M. M., Mohammadou, B. A., Pahane, M., Maiwore, J., & Tatsadjieu, L. N. (2021). Physicochemical, Sensory, and Microbial Characteristics of Kindirmou and Pendidam, Two Traditional Fermented Milks of Adamawa-Cameroon, as Affected by the Fermentation Vessels. Asian Journal of Biotechnology and Bioresource Technology, 7(4), 25-38.

Nakavuma, J. L., Møller, P. L., Jakobsen, M., Salimo, P., & Nasinyama, G. W. (2012). Processing steps and lactic acid bacteria involved in traditional cultured milk (Kwerionik) production in Uganda.