1.1 Background of the Study
Roselle (Hibiscus Sabdariffa) and Rosemary (Rosmarinus Officinalis) are annual plant, which is popular in folk medicines. Extracts of Roselle and Rosemary have shown a broad range of therapeutic effects such as antiobesity, antihypertensive, anticancer and antibacterial. Calyces are considered the most important part of the plant and used in various researches while leaves which are used as vegetables are rarely used. Suleiman et al. (2019) affirmed that herbal formulation may be obtained from extracts from stem, bark or leaves of various plants. Almost all parts of most medicinal plants are useful. Sweet potato (Ipomea batatas) is one of the most important crops worldwide including wheat, rice, maize, potato and cassava. Sweet potatoes possess many positive health benefits including sources of anthocyanins, phenolic compounds and other bioactive compounds. It is an economic source of food energy and also possesses antioxidant activities (Oladoye et al. 2016). The crop tubers have been consumed in various forms in developing countries of Africa, including eating in cooked form, incorporation with yam during pounded yam preparation, processing into flours along with yams for edible dough (such as amala in Nigeria) etc. Globally, food spoilage caused by microorganisms still widely affects all types of food and causes food waste and loss, even in developed countries. It has been estimated that the yearly losses of global food reach up to 40% due to various factors including spoilage by microorganisms. Bacteria, yeast, and molds are the common types of microorganisms responsible for the spoilage of a considerable number of food and food products. Once these microorganisms reach food products, they grow by utilizing the nutrients and produce metabolites that cause food spoilage ( Markson et al. 2014). Foodborne disease is another pervasive food safety problem caused by consumption of contaminated food products, which has been a significant safety concern to public health. Microorganisms are available naturally in the surrounding environment; therefore they can easily reach food during harvesting, slaughtering, processing, and packaging ( Adeogun et al., 2014). These microorganisms can survive under adverse conditions used in the food preservation such as low temperature, modified atmosphere packaging, vacuum packaging, as well as resist conventional pasteurization. Thus, there is a considerable concern among consumers regarding the risk of using synthetic additives for human health that led to decrease the use of these chemicals in food preservation. Therefore, new eco-friendly methodologies are required to reduce the growth of pathogenic bacteria and prolong the shelf-life of food products, without using chemical preservatives. Recently, many researchers investigated the possible utilization of some plant extracts as effective natural preservatives. Traditionally, the crude extracts of different parts of medical plants, including root, stem, flower, fruit, and twigs, were widely used for treatments of some human diseases ( Alhussaen et al. 2011). Medicinal plants contain several phytochemicals such as flavonoids, alkaloids, tannins, and terpenoids, which possess antimicrobial and antioxidant properties. The antimicrobial activities of some plant species have been widely researched. For example, the crude extracts of cinnamon, garlic, basil, curry, ginger, sage, mustard, and other herbs exhibit antimicrobial properties against a wide range of Gram-positive and Gram-negative bacteria (Edmad et al. 2012). In addition, it has been reported that the extracts from Chinese chives and cassia can effectively reduce the growth of Escherichia coli and other bacteria during storage of meat, juices, and milk. The understanding of the mechanism of antimicrobial action of medicinal plants extracts is the first step in the optimal utilization of these extracts as natural antimicrobial agents to extend the shelf-life and maintain the food quality. Therefore, the researcher is to embark on the study of antimicrobial activity of Roselle (Hibiscus Sabdariffa) and Rosemary (Rosmarinus Officinalis) extract against spoilage microbes from spoilt sweet potato sold within Awka Metropolies and their effects on tubers quality parameters.