Using some plant extracts (Thymus vulgaris, Musa sp. and Citrus sinensis) to prolong the shelf life of local soft cheese Sadiyha Yasir Al-Jubory 1* and Ruqya Tariq Habeb Al Habeb 2 1 College of Biotechnology, University of Al-Qadisiyah, Al-Qadisiyah, Iraq 2 Researcher, Al-Qadisiyah, Iraq Abstract Powder, aqueous and phenolic extract, of thyme leaves (Thymus vulgaris) (TVL), orange peels (Citrus sinensis) (CSP), and banana peels (Musa sp) (MSP) were added to pasteurized milk before renneting separately for testing their abilities to prolonging the storage period of local soft cheese. These additives were successful in prolonging the storage period of the soft local cheese to 28, 30, and 40 days respectively compared with the control treatment (no additives (NA)), 15 days only. Powder plant additions were the best from the other additions; orange peel powder was the best one. Sensory evaluation of the cheese revealed that the cheese was accepted by tasters for its qualities represented by flavor, taste, bitterness, and color. The use of natural plant additions to cheese led to prolonging the duration of storage, and we recommend that it can be used in food processing rather than industrial preservatives. Keywords: Thymes, Orange, Banana, Soft Cheese. INTRODUCTION Cheese production is one of the most important traditional industries used to preserve milk ingredients from pollution (1) and to be stored for an extended period of time. The product varies according to the materials used in its production, production and marketing method (2). Soft cheese is considered as one of the most requested cheeses. The cheese is considered as a suitable growth medium for microorganisms leading to the contamination of cheese. The plant additions are natural substances with many benefits. Some of them work as antioxidants and antimicrobials. Also, they are rich in essential nutrients such as the availability of thyme, fruits of oranges, and bananas. Unfortunately, the peels of these fruits are trashed away without benefit. So our current study was aimed to use leaves of thyme and the peels of bananas and oranges as preservatives to prolong the storage duration of local soft cheese. MATERIALS AND METHODS Collection of plant samples Dried TVL, CS, and MS were obtained from local markets in Al-Qadisiyah Governorate. TVLs were cleaned out of dust and impurities. The fruits of banana and orange were peeled out, and the crusts were left out to dry and crushed down to powder form. Phenolic compounds extraction The method of Malik et al., (2008) (3) was adopted with some modifications, where 20gm of plant powder was taken from each substance and placed in a filter paper in the Soxhlet. Moreover, 300 ml of petroleum ether was added until the extract became colorless and removed. Moreover, it was left to dry, then returned to the Soxhlet, and 300ml 70% methanol was added at until the extract became colorless. Concentrated the extract in the rotary evaporator was performed until its size became 5ml. Hydrochloric acid was added to remove the stearic bonds between the acid particles in the case where they were existed, and then the mix was incubated in an 80⁰C water bath for 1hr. Then, the extract was placed in a separating funnel and 10ml ethyl acetate was added to three times. It was left for a while, and the top layer was collected and dried (4). Preparation of the water extract Gülçin et al., (2003) (5) method was adopted to extract the active substances by mixing 25gm of powder with 250ml distilled water (DW). Then, the mix was left 30min on a magnetic stirrer, then was filtered by a gauze for two consecutive times, then concentrated the filter by a rotary evaporator, dried in an oven at 40°C, was placed in dark bottles, and was saved in a refrigerator until use. Milk samples The full-fat milk was brought from the Al-Qadisiyah Cow’s Station in the morning in sterile bottles (from the morning ring). Milk was tested to determine some chemical and physiological characteristics such as temperature, acidity, fat, pH, density, and boiling, and the contamination by microorganisms was evaluated to ensure its safety for human consumption. Cheese processing and adding plant extracts The Iraqi soft cheese was produced using a protocol from the Al-Dahan (1983) (6) by pasteurizing the milk at 63⁰C for 30min and cooled to 35⁰C. The traditional rennet from local markets was added after it was dissolved in DW at 1%. Salt, NaCl, at 0.25% was added. The hot water (WE) of Thyme (WET), Citrus (WEC), and Musa (WEM), and the phenolic extract (PhE) of Thyme (PhET), Citrus (PhEC), and Musa (PhEM), and the powder (P) of Thyme (PT), Citrus (PC), and Musa (PM) were added separately before clotting the milk at the concentrations mentioned in table (1). The clot was cut after coagulation and left for 5min, then it was placed in a gauze, squeezed, and drained. The clot was packed in plastic containers preloaded with pre-boiled whey and stored in a refrigerator at 7±2⁰C until the appearance of unwanted odor, color, or appearance growth of microorganisms. A piece of cheese was taken for the sensory evaluation and the chemical analyses on the first day and every 10 days for 40 days. The chemical tests, lipid ratio and acidity, were measured according to the standard method from (7), and the pH was measured according to (8). The percentage of the yield was measured according to the following formula: Product cheese / Milk weight x 100 (7). Sadiyha Yasir Al-Jubory et al /J. Pharm. Sci. & Res. Vol. 11(3), 2019, 767-773 767