ReseaRch PaPeR Journal of Agricultural and Marine Sciences 2022, 27(2): 66–73 DOI: 10.53541/jams.vol27iss2pp66-73 Received 5 December 2021 Accepted 6 march 2022 Evaluation of physical and chemical properties and total phenolic content in baker’s yeast obtained from grape juice Sawsan Mahmood*1, Ali Ali2, Ayhem Darwesh3, Wissam Zam4 Sawsan Mahmood*1( ) sawsanmahmood480@gmail.com,1PhD student at the Department of Food Technology, Faculty of Technical Engineer- ing, Tartous University. 2Professor at Faculty of Technical Engineering, Tartous University. 3Professor at Faculty of Technical Engineering, Tar- tous University. 4Professor at Faculty of Pharmacy, AL- Wade University. Introduction Fermentation is the process of using microorgan-isms to produce valuable products, such as an-tibiotics, industrial enzymes, food, and chemi- cals. Microorganisms which multiply predominantly by budding are collectively called “yeasts” (Saranraj et al., 2017). Phaff (1990) gave the definition for yeasts as unicellular eukaryotes, which at some stage in their life cycle, divide by budding. The known organisms is the strain of Saccharomyces cerevisiae used in the brewing and baking industries. If the term “yeast” is not further specified, Saccharomyces cerevisiae is the commonly re- ferred organism. This strain of yeast has been extensively studied and applied widely both in the laboratory and in industry. Baker’s yeast (Saccharomyces cerevisiae) is one of the oldest products of industrial fermentation. It is still one of the most important fermentation products based on the volume of sales and its use for bread making, a stable food for large section of world population. The Baker’s yeast Saccharomyces cerevisiae has been associated with human beings for more than 6000 years due to its use in food production, baking, wine and beer (Saranraj et al., 2017). Saccharomyces cerevisiae was the first eukaryotic or- ganism to be sequenced in 1996 (Goffeau et al., 1996), and is clearly the most ideal eukaryotic microorganism for biological studies. The impact of Baker’s yeasts on the production, quality and safety of foods and beverages is intimately linked to their ecology and biological activ- ities. Recent advances in understanding the taxonomy, ecology, physiology, biochemistry and molecular biolo- gy of Baker’s yeasts have stimulated increased interest in foods and beverages. This has led to a deeper under- standing of their roles in the fermentation of established products, such as bread, beer and wine. As the food industry develops new products and processes, yeasts present new challenges for their control and exploitation. Food safety and the linkage between diet and health are the issues of major concern to the modern con- تقييم اخلواص الفيزايئية والكيميائية واحملتوى الفينويل الكلي يف مخرية اخلبز املأخوذة من عصري العنب سوسن حممود * ١ ، علي علي ٢ ، أيهم درويش ٣ ، وسام زم ٤ Abstract. Baker`s yeast is mainly produced from molasses in various parts of the world, and other sources, in- cluding grape juice. In this study, the grape juice was chosen. This study aimed to produce a biomass from dry baker`s yeast. Its physical and chemical properties was evaluated. The biomass from baker’s yeast S. cerevisi- ae was equal to 41.50±0.01 g/L. The following fermentation conditions, i.e. temperature (30.1oC), pH (4.75), sug- ar concentration (158.36 g/L), ratio of carbon to nitrogen (11.9), and initial concentration of yeasts (2.5 g/L) were used. The fermentation was carried out for a period 12 h. Grape juice was subjected to four different heat treat- ments as follows: pasteurized grape juice at (65, 70, and 75oC) for 10 min, and sterilized grape juice in the au- toclave at 121oC for 20 min. The effect of each treatment was determined on inhibition of the enzyme polyphe- nol oxidase present in grape juice. The total phenolic content was determined in the yeast. Heat treatments gave the best phenolic content in the resulting yeast. The heat treatments of the juice succeeded in reducing the activ- ity of the enzyme polyphenol oxidase and autoclave heat treatment gave the best phenolic content in the yeast. Keywords: : Baker`s yeast, grape juice, fermentation, phenolic content. امللخص:يتــم إنتــاج اخلمــرة املســتخدمة يف املخابــز بشــكل أساســي مــن دبــس الســكر يف أجــزاء خمتلفــة مــن العــامل ، ومصــادر أخــرى ، مبــا يف ذلــك عصــر العنــب. يف هــذه الدراســة مت اختيــار عصــر العنــب. وعليــه كان اهلــدف مــن هــذه الدراســة هــو إنتــاج كتلــة حيويــة مــن مخــرة املخابــز اجلافــة. حيــث مت تقييــم اخلــواص الفيزايئيــة والكيميائيــة للخمــرة. فقــد كانــت الكتلــة احليويــة مــن مخــرة اخلبــاز S. cerevisiae تســاوي ٤١.50 ± 0.0١ جــم / لــر. وقــد مت اســتخدام ظــروف التخمــر التاليــة ، درجــة احلــرارة )٣0.١ درجــة مئويــة( ، و درجــة احلموضــة )٤.75( ، وتركيــز الســكر )١58.٣6 جــم / لــر( ، ونســبة الكربــون إىل النيروجــن )١١.9( ، والركيــز األويل للخمائــر )٢.5 جــم / لــر(. مت إجــراء التخمــر ملــدة ١٢ ســاعة. تعــرض عصــر العنــب ألربــع معامــات حراريــة خمتلفــة علــى النحــو التــايل: عصــر العنــب املبســر عنــد )65 ، 70 ، 75 درجــة مئويــة( ملــدة ١0 دقائــق ، وعصــر العنــب املعقــم يف جهــاز التعقيــم عنــد ١٢١ درجــة مئويــة ملــدة ٢0 دقيقــة. مت حتديــد أتثــر كل معاملــة علــى تثبيــط إنــزمي بوليفينــول أوكســيديز املوجــود يف عصــر العنــب و حتديــد حمتــوى الفينــول الكلــي يف اخلمــرة. أعطــت املعاجلــات احلراريــة أفضــل حمتــوى فينــويل يف اخلمــرة الناجتــة. جنحــت املعاجلــات احلراريــة للعصــر يف تقليــل نشــاط إنــزمي بوليفينــول أوكســيديز وأعطــت املعاجلــة احلراريــة جبهــاز التعقيــم أفضــل حمتــوى فينــويل يف اخلمــرة. الكلمات املفتاحية: مخرة املخابز ، عصر العنب ، التخمر ، حمتوى الفينول. 67Research Paper Mahmood, Ali, Darwesh, Zam sumer and Baker’s yeasts are emerging in this con- text (Saranraj et al., 2017). On the positive side, there is increasing interest in using Baker’s yeasts as novel probiotic and biocontrol agents, and for the nutri- ent fortification of foods (Gelinas, 2006; Prem Kumar et al., 2015a). Baker’s yeast, Saccharomyces cerevisi- ae, is still one of the most important biotechnological products because of its several industrial applications. Baker’s yeast as a commercial product has several formulations that can be grouped into two main types: compressed yeast, called fresh yeast, and dried yeast (Beudeker et al., 1990). Compressed yeast is the tra- ditional formulation of baker’s yeast and is ready for immediate use. Dried yeast is available in two forms: active dry yeast (ADY) and instant dry yeast (IDY). Ac- tive dry yeast (ADY) is normally sold in airtight pack- ages, vacuum seal or filled with an inert gas such as nitrogen. It is not a problem to maintain quality, but it should be rehydrated before use. Unlike ADY, instant dry yeast (IDY) does not have the cell damage during rehydration. IDY is the most expensive among the three type of baker’s yeast. Baker’s yeast is marketed in two ways, either as compressed cakes or as a dry pow- der, however there is also a saleable intermediate of the process known as ‘Cream yeast’ (Gill et al., 2013). Yeast are a unicellular fungi or plant-like microorgan- ism that exists in or on all living matter i.e. water, soil, plants, and air. They are microbial eukaryote, associated with ascomycetes and are rich in protein and vitamin B (Dunn et al., 2015). As a living organism, yeast primarily requires sugars, water and warmth to stay alive. In addi- tion, albumen or nitrogenous material is also necessary for yeast to thrive. There are hundreds of different species of yeast identified in nature, but the genus and species most commonly used for baking is Saccharomyces cerevisiae. The scientific name Saccharomyces cerevisiae, means a mold which ferments the sugar in cereal (i.e. saccha- ro-mucus cerevisiae) to produce alcohol and carbon di- oxide. Yeasts are usually spherical, oval or cylindrical in shape and a single cell of S. cerevisiae is around 8 μm in diameter. Each cell has a double-layered wall, which is permeable to certain substances and food material is tak- en into the cell and metabolites (Slonimski et al., 2013). Cell division or cell reproduction generally takes place by budding. In the budding process, a new cell forms as a small outgrowth of the old cell, the bud grad- ually enlarges and then separates. Although, most yeast reproduce only as single cells, under some conditions some yeasts can form filaments (Madigan et al., 2003; Sivasakthivelan et al., 2014). Yeasts flourish in habitats where sugars are pres- ent, such as fruits, flowers and bark of trees. Howev- er, commercial yeasts of today are quite different from wild strains due to genetic manipulation, allowing them to grow in previously unsuitable conditions (Liti et al., 2009; Prem Kumar et al., 2015b). Yeasts are of great economic importance. Yeasts, especially different strains of Saccharomyces cerevisi- ae have long been used for the production of alcoholic beverages, solvents and other chemicals. In the modern bakery, yeasts are used for manufacturing of different kinds of bread and confectionaries. It is responsible for leavening the dough and imparting a delicious flavor to the product (Warringeret al., 2011). Molasses is the most used raw material in the produc- tion of Baker’s yeast, and it may be sourced from sugar beet, or sugar cane, and it contains about 50-55% of fer- mentable sugars, and some vitamins and minerals. These are important in cell proliferation containing fermentable sugars, such as date and grape juices (Gelinas et al., 2000). Yeasts have a positive image with consumers, as they are considered a safe source of ingredients and additives for food processing (Boze et al., 1992; Bekatorou et al., 2006; Tsunatu et al., 2017). Preparations of baker’s and brew- er’s yeasts have been available for many years as dietary, nutrient supplements because of their high contents of B vitamins, proteins, peptides, amino acids and trace min- erals. Yeasts are often considered as an alternative source of protein for human consumption (Buzzini et al., 2005; Chaucheyras-Durand et al., 2008; Pienaar et al., 2012). Many products are now derived from yeasts and, according to Abbas (2006), about 15–20% of the global industrial production of yeasts is used for this purpose. The production of antioxidants, aromas, flavors, colors and vitamins could be done by yeasts. Interest in food phenolics has increased, because of their antioxidant and free radical scavenging abilities (Lugasi and Hovari, 2003), metal chelators and enzyme modulators (Dulg- er et al., 2002). Many phenolics can exhibit antioxidant activity as their extensive, conjugated electron systems allow ready donation of electrons, or hydrogen atoms, from the hydroxyl moieties to free radicals. However, the antioxidant efficacy, in terms of reaction stoichiometry and reaction kinetics may vary considerably (Lugasi et al., 2003). This is dependent on structural features, such as the number and positions of the hydroxyl moieties on the ring systems, and the extent by which the unpaired electron in the oxidized phenolic intermediate can delo- calise throughout the molecule. Thus, most phenolics, especially flavonoids are very effective scavengers of hy- droxyl and peroxyl radicals. Phenolics are chelators of metals and inhibit the Fenton and Haber-Weiss reactions abilities (Lugasi et al., 2003; Dulger et al., 2002), which are important sources of active oxygen radicals. Phenolic compounds inhibited the development of cancerous tu- mours, reduce a risk for cardiovascular disease, and have showed antibacterial, anti-inflammatory, antispasmodic and anti-diarrheic properties (Abdoul-latif et al., 2012). Fermentation is a good technology with great poten- tial for application on the production or extraction of an- tioxidant active compounds from natural sources. New bioactive compounds could be found during fermenta- tion. Moreover, modification of fermentation process could be tailored to increase the bio accessibility of bio- 68 SQU Journal of Agricultural and Marine Sciences, 2022, Volume 27, Issue 2 Evaluation of physical and chemical properties and total phenolic content in baker’s yeast obtained from grape juice active compounds. Production of bioactive compounds yet remains a quite unexplored potential, which could be accomplished by utilizing new fermentation process. Therefore, in the future, it can be anticipated that fer- mentation could be used to design food with health ef- fects. Some fermentation processes are available on the applications of production of antioxidant activity com- pounds (Shahat, 2017). However, the underlying mech- anisms affecting anti-oxidative activity during fermenta- tion are varied, and the production of antioxidant active compounds during fermentation (Hur et al., 2014). Some of the most compelling evidence of a protec- tive effect of diets against cancer, in recent years, is the evidence on the intake of fruits and vegetables (Block et al., 1992; Fokou et al., 2017). EPIC (European Pro- spective Investigation into Cancer and Nutrition) is an important study that indicates that these retrospective- ly obtained results, at least respecting to cancer, might have been somewhat overestimated, however, still a significant reduction of consumption of fruits and veg- etables on colorectal cancer (Bouayed0 et al., 2010). Polyphenols can further act by inhibiting cell pro- liferation, which is deregulated in cancer. This inhi- bition has been demonstrated in vitro in many tumor cell lines. Although the anti-proliferative effects of polyphenols in general and in particular of flavonoids and iso-flavonoids in cell cultures seems well estab- lished, there are relatively few data regarding the in vivo anti proliferative activity, and virtually nothing is known about the clinical relevance of this bioactivity (Birt et al., 2001). This anti-proliferative effect suggests that polyphenols may have an effect via regulating the cell cycle or inducing apoptosis in tumor cells. In fact, many studies have shown the effect of polyphenols on the cell cycle of tumor cells in cultures in in vitro assays. Therefore, in this presented study, grape juice was selected as the sole source of carbon for producing dry biomass from yeast due to its richness in phenolic com- pounds. Then the phenolic content of the yeast obtained from grape juice was evaluated. This study distinguished from previous studies using an organic medium, while previous studies used commercial media to obtain dry yeast with good phenolic content (Shaha, 2017). It is known that grapes contain a good amount of the enzyme, polyphenol oxidase, which causes oxidation of phenolic compounds and reduces their quantity. It also causes enzymatic browning, which may negative- ly effect of the final product quality. In this study, the effect of heat treatment on the activity of the enzyme polyphenol oxidase was evaluated at different tem- peratures with the aim of choosing the best heat treat- ment in reducing the enzyme activity and thus main- taining a good phenolic content in the resulting yeast. Materials and Methods Commercial materials All materials used in these experiments are collected from HiMeda Company, Mumbai, India. Glucose and vitamin solutions were sterilized by filtration and added to the autoclaved medium. Origin and Reactivation of the Yeast S. cerevisiae Dried powder yeast form of S. cerevisiae (ATCC20408/ S288c) was used in this study. It was produced by the Biomatric-The Biostability Company. The yeast was re- activated on agar plates containing YPGA medium com- posed of yeast extract 10 g/L, peptone 10 g/L, glucose 20 g/L, agar 20 g/L with a pH 6, incubated at 30oC for 24 h. Preparation of Grape Juice Baladi grapes (Figure 1), which is one of the white grape varieties, originating in Spain were used. It is known as Cayetana grape. Baladi grapes are among the varieties available in Syria. Its yield is up to 20%. It is a domestic variety characterized by the size of its large mass and has a single conical shape. The grains are spherical in shape, large size, yellowish-white in color, and the peel is thin and light pink in color. The pulp is flaky, has a good taste, has a characteristic flavor, it is a late-ripening variety. It is a popular and luxurious table variety, suit- able for remote transportation and long winter storage. Baladi grape samples were collected from the Sheikh Badr area in the countryside of Tartous city in Syria. The grape berries were removed from their clusters, cleaned and washed with warm water. The juice was extracted by breaking and pressing in doubly folded cloth. Figure 1. The baladi grape 69Research Paper Mahmood, Ali, Darwesh, Zam Thermal Treatment for Grape Juice The heating effect on the grape juice was pasteurized at (65, 70 and 75oC) for 10 min, while fourth treatments was sterilized grape juice in the autoclave at 121 oC for 20 minutes. Then the effect of each heat treatment on inhibiting the activity of the enzyme polyphenol oxidase in grape juice was determined by estimating the pheno- lic content in the yeast. Preparation of Culture Medium Based on Grape Juice and Inoculums The method cited by Kocher and Uppal (Kocher et al., 2013) was used with minor modifications. The obtained grape juice from the above preparation was supplement- ed by mineral salts: magnesium sulfate 0.44 g, urea 12.70 g, and ammonium sulfate 5.30 g. Finally, the medium was distributed in an Erlenmeyer of 250 mL with a ra- tio of 100 mL per flask and sterilized at 120 oC for 20 min. The pre-culture was obtained by inoculating two colonies of the yeast S. cerevisiae in 250 mL shake flasks containing 100 mL of grape juice, mentioned above. The pre-culture was incubated at 30 oC for 3 h, and used fur- ther as inoculums for the yeast biomass production. Fermentation Process The fermentation was carried out within a biological fer- menter with a capacity of 6 liters with an engineering design and initial volume of the fermentation medium (i.e. grape juice) was 3 liters. The initial conditions for the fermentation process were: temperature (30.11 oC), pH (4.75), sugar concentration (158.36 g/L), ratio of car- bon to nitrogen (11.9), initial concentration of yeasts (2.5 g/L), stirrer speed (630 r.p.m), air flow (20 min/L), and period fermentation was 12 h. The temperature of the fermentation medium was set at the required de- gree using the cooling and heating coils in the biolog- ical fermenter. The pH was also adjusted by pumping appropriate quantities of 10 % (w/v) NaOH and 10% (v/v) H2SO4 as needed into the fermentation medium. Biomass Concentration The measurement of biomass was followed by estima- tion of cell dry weight, expressed in g/L. One mL of yeast culture was centrifuged at 5000 rpm for 5 min. The su- pernatant obtained was washed twice with water and dried by incubation at 105 oC until at a constant weight (Jiménez-Islas et al., 2014). Total Phenolic Content (TPC) in the Yeast Biomass Total phenolic content of yeast extracts obtained from grape juice medium was estimated using the Fo- lin-Ciocalteu reagent method (Kahkonen et al., 1999; Ainsworth and Gillespie, 2007). One ml of each sample extracts were mixed with 250 μL of 10% (v/v) Folin-Ci- ocalteu reagent, followed with the addition of 500 μL saturated sodium carbonate (10%, w/v aqueous solu- tion) after 2 min of incubation at room temperature. The mixture was placed in the dark for 1 hour. Absorbance was then measured at λ750 nm. The concentration of to- tal phenols was calculated based on a calibration curve using gallic acid. The phenol content was expressed as gallic acid equivalent (GAE), which reflects the phenol content, as the amount of gallic acid units in liter of ex- tract (mg GAE L-1). Three replicates were used for total phenolic content. Physicochemical Characteristics of the Ob- tained Yeast Proximate composition: total protein, nitrogen, moisture, dry matter and ashes were determined in accordance with the AOAC procedures (1975; 1990). Total carbohy- drates were determined through the colorimetric meth- od from Dubois et al. (1958). Total lipids were extracted through the procedure of Blight et al. (1959) and deter- mined gravimetrically. Fibers were quantified through the method from Asp et al. (1983). Density, pH and ener- gy of dry yeast were determination with the COFALEC (2012): General characteristics of dry baker’s yeast. Test for dispersibility in water: Weigh 5 g of dry bak- er’s yeast or 20 g of fresh baker’s yeast into a 400 ml bea- ker and add 50 ml of distilled water at 40 oC. Leave the product undisturbed for 5 min and thereafter, stirred for 2 min. Take into a one liter graduated cylinder, 900 ml of distilled water at 40 oC in the case of dry baker’s yeast and at 30 oC for fresh baker’s yeast. Pour the slurry from the beaker into the water in the graduated cylinder. Wash the beaker with 50 ml of distilled water, poured it into the cylinder and left it undisturbed for 5 min. Checked for any deposits at the bottom of the cylinder. If no deposits appeared at the bottom of the cylinder, the material shall be considered to have passed the test (Rad et al., 2017). Dough Raising Capacity Fresh baker’s yeast (4 g) or 1.0 g of dry baker’s yeast with 100 g of wheat flour were mixed. Sucrose (1.0 to 1.5 g) was added to a suitable quantity of water (about 55 ml). These were mixed by Knead well Press into a glass beaker until formed a dough. The level of the dough by means of a scale, from the bottom of the beaker was not- ed. It was kept covered for one h at 27 oC. At the end of this period, level was recorded again. The product shall be deemed to have satisfied the test if the level was at least 80 percent of the original for dry baker’s yeast and 110 percent for fresh baker’s yeast (Rad et al., 2017). Yeast survivability was determined as CFUs per gram of dry matter. A microbial test can be used to measure the viability and survivability of yeast cells. Twenty-five grams of yeast was mixed with 175 mL of water. The via- bility of the suspensions was checked by plate counting. Yeast cell suspensions were counted on yeast extract glu- cose-chloramphenicol (YGC) agar (YGC Agar, Merck) after 5 days of incubation at 25 oC. Logarithmic dilutions were carried out in saline, and diluted suspensions were 70 SQU Journal of Agricultural and Marine Sciences, 2022, Volume 27, Issue 2 Evaluation of physical and chemical properties and total phenolic content in baker’s yeast obtained from grape juice cultured on YGC agar and incubated at 25 oC for 5 days (Rad et al., 2017). Statistical analysis Experiments were performed in three replicates and all results were expressed as mean ± standard deviation (SD) using Windows software, version 7.0 (Origin Lab, 2010). Results and Discussion Biomass from baker’s yeast S. cerevisiae in grape juice medium was determined as a sole carbon source, and it was equal to 41.5±0.01 g/L at the fermentation condi- tions of temperature (30.11oC), pH (4.75), sugar concen- tration (158.36 g/L), ratio of carbon to nitrogen (11.9), initial concentration of yeasts (2.5 g/L) and a period of fermentation (12 h). Similarly, Nancib et al. (1997) ob- tained biomass from baker’s yeast S. cerevisiae was 40 g/L, when date fruit byproducts were used. Khan et al. (2017) used six different strains of S. cerevisiae in fer- mentation medium containing date extract (with 60% sugars), 2 g/L ammonium sulfate and 50 mg/L biotin. Their results showed that the theoretical yields were about 42.8%. In addition, Al Obaidi et al (1986) studied two substrates (i.e., date syrup and molasses) for the propagation of baker’s yeast strain S. cerevisiae on a pi- lot plant scale. The results showed that higher produc- tivity of baker’s yeast was observed when date extract was used. In fact, the optimal biomass production (6.3 g/L) was depicted at 24 h using Saccharomyces cerevisiae DIV13Z087C0VS on a medium containing sweet cheese as a sole carbon source (Boudjema et al., 2015). On the other hand, the production of baker’s yeast from apple pomace gave a yield of 0.48 g/g (Bhushan et al., 2006). Therefore, it was concluded from these studies that the medium containing the grape juice as a sole carbon source is an excellent fermentation medium for baker’s yeast production. The total phenolic content was esti- mated by Folin-Ciocalteu method using gallic acid as the standard reference (Figure 2). Total phenolic content in the yeast extract were 1275.39±0.01, 1623.3±0.01, 1739.17±0.01, and 2087±0.01 mg/L at thermal treatment of grape juice 65, 70, 75, and in autoclave at 121oC, respectively. It was noted that the heat treatment of the juice succeeded in reducing the activity of the enzyme polyphenol oxidase by about 50% at temperature 65oC, 70% at temperature 70oC, 75% at temperature 75 oC, and 90% at temperature 121oC, re- spectively. The best heat treatment was observed in the case of autoclave, as it helped to maintain the best phe- nolic content in the resulting yeast. Shahat (2017) were determined for four commercial mediums after steril- ized in the autoclave at 121 °C for 20 min. The pheno- lic contents were 1387±0.01, 1990±0.01, 1129±0.01 and 982±0.01 mg/L for the yeast-peptone-dextrose medium, corn meal, oat meal and sugar cane medium, respective- ly. The best result was with corn meal, and was close to the result of this current study at 121 °C for 20 min. Con- sequently, the yeast produced from grape juice can play an important part in the human health and nutrition due Figure 2. Standard calibration urve for galic acid at a wavelength of 765 nm 71Research Paper Mahmood, Ali, Darwesh, Zam to its biological effectiveness and its antioxidant and an- ticancer activities. The results of physico-chemical char- acteristics of yeast are shown in Table 1 with the corre- sponding values according to the COFALEC (2012). Dry yeast cells was dispersed in water as required and no yeast cell was deposited. The level of dough became 80 percent of the original as required , and yeast cells have satisfied the test. Colony counting of the samples showed that the number of cfu/mg yeasts was 15×1010 cfu per milligram in the dry matter of yeast. According to the COFALEC (2012), Coliform count was below 1000 cfu/g, thus the yeast produced from grape juice was acceptable. Conclusion This study showed that the heat treatments of the juice reduced the activity of the enzyme polyphenol oxidase and autoclave heat treatment gave the best phenolic content in the yeast. It is clear that the use of grape juice can be possible as the sole source of carbon in order to produce bread yeast. It demonstrated a good yield of dry biomass from bread yeast and these could be used by food industries, and it contained high level of phenolic content. It can also make a nutritional supplement and could beneficial to human health. References Abbas CA. (2006). Production of Antioxidants, Aromas, Colours, Flavours, and Vitamins by Yeasts. In: yeasts in food and Beverages (eds. Querol A, Fleet GH). Springer Verlag, Berlin, chapter, 10, pp. 285-334. Abdoul-latif FM, Bayili RG, Obame LC, Bassolé IHN, Dicko MH. (2012). Comparison of phenolic com- pounds and antioxidant capacities of traditional sorghum beers with other alcoholic beverages. Af- rican Journal of Biotechnology 11(81): 14671-14678. Ainsworth EA, Gillespie KM. (2007). Estimation of total phenolic content and other oxidation substrates in plant tissues using Folin-Ciocalteu reagent. Natural Protocol 2: 875-877. Al Obaidi ZS, Mohamed NA, Hasson NA, Jassem M A. (1986). Semi-Industrial production of Baker’s yeast using date extract and molasses. Journal of Agricul- tural and Marine Sciences. Water Resource Research 5: 162–174. AOAC. (1975). Association of Official Agricultural Chemists. Official Methods of Analysis. HORWITZ, W., Washington, D.C. AOAC. (1990). Association of Official Agricultural Chem- ists, Official Methods of Analysis, 15th edition, Arlington. Aziz H, Zahra K. (2017). A comparative study on dif- ferent methods for the evaluation of baker’s yeast bioactivity, International Journal of Food Properties 20(1):100-106. Bekatorou A, Psarianos C, Koutinas AA. (2006). Pro- duction of Food Grade Yeasts. Food Technology and Biotechnology 44: 407-415. Beudeker FR, Van Dam HW, Van der Plaat JB, Vellenga K. (1990). Developments in baker’s yeast production. In Yeast Biotechnology and Biocatalysis, ed. H Ver- achtert. New York: Marcel Dekker, Inc. pp 103-146. Bhushan S, Joshi V K. (2006). Baker’s yeast production under fed batch culture from apple pomace. Journal of Science and Industrial Research 65: 72-76. Birt DF, Hendrich S, Wang W. (2001). Dietary agents in cancer prevention: flavonoids and iso flavonoids. Pharmacol Therapeut 90: 157-177. Blight E G, Dyer W J. (1959). A rapid method of total lipid extraction and purification. Canadian Journal of Biochemistry and Physiology 37(7): 911-917. Block G, Patterson B, Subar A. (1992). Fruit, vegetables, and cancer prevention: a review of the epidemiolog- ical evidence. Nutr Cancer, 18: 129. of Biochemistry and Physiology 37(7): 911-917. Bouayed J, Bohn T. (2010). Exogenous antioxidants-Dou- ble-edged swords in cellular redox state: Health ben- eficial effects at physiologic doses versus deleterious effects at high doses. Oxidative Medicine and Cellu- lar Longevity 3: 228-37. Table 1. The Physico-chemical characteristics of the obtained yeast. parameter Requirement value for dry yeast Result value for obtained yeast Moisture (%) Dry matter (%) Total protein (%, dry matter) Nitrogen (% / dry matter) Total carbohydrate (%, dry matter) Total fat (%, dry matter) Fibers (%, dry matter) Ashes (%, dry matter) Density (g/cc) pH value Energy value (kcal/100 g dry matter) < 8% (92-96)% 46%±10% 7.5%±1.5% 20%±9% 6%±2% 28%±5% 6%±2% (0.75-0.95) 6±2 373 – 310 kcal/100g dry matter 5±0.013% 95±0.021% 42.5±0.014 % 7 ±0.0321% 18±0.014% 7.5±0.0342 % 23±0.015 % 4±0.0212 % 0.89±0.012 6±0.01 324.975±0.01 kcal/100g dry matter 72 SQU Journal of Agricultural and Marine Sciences, 2022, Volume 27, Issue 2 Evaluation of physical and chemical properties and total phenolic content in baker’s yeast obtained from grape juice Boudjema K, Fazouane-naimi F, HellaL A. (2015). Op- timization of the Bioethanol Production on Sweet Cheese Whey by Saccharomyces cerevisiae DIV13- Z087C0VS using Response Surface Methodology (RSM). Rom. Biotech. Lett. 20: 10814–10825 Boze H, Moulin G, Galzy P. (1992). Production of food and fodder yeasts. Critical Reviews in Biotechnology 12: 65-86. Buzzini P, Gasparetti C, Turchetti B, Cramarossa MR, Vaughan-Martini A, Martini A, Pagnoni UM, Forti L. (2005). Production of volatile organic compounds (VOCs) by yeasts isolated from the ascocarps of black (Tuber melanosporum Vitt.) and white (Tuber magnatum Pico) truffles. Archives of Microbiology. 184: 187-93. Chaucheyras-Durand F, Walker ND, Bach A. (2008). Effects of active dry yeast on the rumen microbial ecosystem: Past, present and future. Animal Feed Science and Technology. 145: 5-26. COFALEC (2012): General characteristics of dry baker’s yeast. Confederation of EU Yeast Producers, pp.1-7. DRAFT UGANDA STANDARD (DUS) 1717:2017. Bak- er’s Yeast — Specification. ICS 67.220.20. Dubois M, Gilles KA, Hamilton JK, Rebbers PA, Smith F. (1958). Colorimetric method for determination of sugars and related substances. Analitical Chemistry, 28(3): 350-356. Dulger B, Ergul CC, Gucin F. (2002). Antimicrobial ac- tivity of the macrofungus Lepista nuda. Fitoterapia, 73(7-8): 695–697. Dunn B, Levine RP, Sherlock G. (2015). Microarray Karyotyping of Commercial Wine Yeast Strains Re- veals Shared, as well as Unique, Genomic Signatures. BMC Geno. 6(1): 53. Fokou TJBH, Menkem EZ, Yamthe LRT, Mfopa AN, Kamdem MS, Ngouana V, TSAGUE IFK, BOYOM FF. (2017). Anti-yeast potential of some Annonace- ae species from Cameroonian biodiversity. Interna- tional Journal of Biological and Chemical Sciences., 11(1): 15-31. Gelinas P, McKinnon C. (2000). Fermentation and mi- crobiological processes in cereal foods, in handbook of cereal science and technology, 2nd Ed., Kulp K, Ponte JG. Jr. Ed. Marcel Dekker Inc. pp.741-754. Gelinas, P. (2006). Yeast in bakery products science and technology, Y.H. Hui, H. Corke, I. De Leyn, W.K Nip and N. Cross Ed. Blackwell Publishing. pp.173-191. Gill FR, Saez IC, Prieto J. (2013). Genetic and phenotyp- ic characteristics of Baker’s yeast: Relevance to Bak- ing. Annual Review of Food Science and Technology. 4: 191-214. Goffeau A, Barrell BG, Bussey H, Davis RW, Dujon B, Feldmann H, Galibert F, Hoheisel JD, Jacq C, Johnston M, Louis EJ, Mewes HW, Murakami Y, Philippsen P, Tettelin H, Oliver SG. (1996). Life with 6000 Genes. Sci.74: 563-567. Hur SJ, Lee SY, Kim YC, Choi I, Kim GB. (2014). Effect of fermentation on the antioxidant activity in plant- based foods. Food Chem. 160: 346-356. Jiménez-Islas D, Páez-Lerma J, SotoCruz NO, Gracida J. (2014). Modelling of Ethanol Production from Red Beet Juice by Saccharomyces cerevisiae under Ther- mal and Acid Stress Conditions. Food Technol. Bio- technol. 52: 93– 100. Kahkonen MP, Hopia AI, Vuorela HJ, Rauha JP, Pihlaja K, Kujala TS, Heinonen M.1999. Antioxidant activity of plant extracts containing phenolic compounds. Jour- nal of Agricultural and Food Chemistry.47: 3954-3962. Khan JA, Abulnaja KO, Kumosani TA, Abou-Zaid AA. (2017). Utilization of Saudi date sugars in production of baker’s yeast. Bioresour. Technol. 1995, 53, 63–66. Foods, 6, 64 17 of 17. Kocher GS, Uppal S. (2013). Fermentation variables for the fermentation of glucose and xylose using Saccha- romyces cerevisiae Y2034 and Pachysolan tannophilus Y-2460. Indian Journal of Biotechnology. 12: 531–536. Liti G, Carter DM, Moses AM, Warringer J, Parts L. (2009). Population Genomics of Domestic and Wild Yeasts. Nat. 458: 337-341. Lugasi A, Hovari J. (2003). Antioxidant Properties of Commercial Alcoholic and Nonalcoholic Beverages, Nahrung/Food 47: 79–86. Madigan MT, Martinko JM, Parker J. (2003). Brock Bi- ology of Microorganisms, 10th Edition, Pearson Ed- ucation Inc. Nancib N, Nancib A, Boudrant J. (1997). Use of waste date products in the formation of baker’s yeast bio- mass by Saccharomyces Cerevisiae. Bioresource Technology. 60: 67–71. Phaff, HJ. (1990). Isolation of yeasts from natural sources in Isolation of Biotechnological Organisms from Nature (Labeda, D. P., Ed.). McGraw-Hill, New York. pp. 53–79. Pienaar GH, Einkamerer OB, van der Merwe HJ, Hugo A, Scholtz GDJ, Fair MD. (2012). The effects of an active live yeast product on the growth performance of finishing lambs. South African Journal of Animal Science 42(5): 464-468. Prem Kumar D, Jayanthi M, Saranraj P, Kavi Karunya S. (2015a). Effect of Potassium Sorbate on the inhibition of growth of fungi isolated from spoiled Bakery prod- ucts. Arch Life Sciences. 1(4): 217-222. Prem Kumar D, Jayanthi M, Saranraj P, Kavi Karunya S. (2015b). Effect of Calcium propionate on the inhibi- tion of fungal growth in Bakery products. Indo-Asian Journal of Multidisciplinary Research. 1(3): 273-279. Rad HA, Kasaie Z. (2017). A comparative study on dif- ferent methods for the evaluation of baker’s yeast bioactivity. International Journal of Food Properties. 73Research Paper Mahmood, Ali, Darwesh, Zam Taylor&Francis group. VOL. 20, NO. 1: 100–106. http://dx.doi.org/10.1080/1094 2912.2016.1141297. Saranraj P, Sivasakthivelan P, Suganthi K. (2017). Baker’s Yeast: Historical Development, Genetic Character- istics, Biochemistry, Fermentation and Downstream Processing. Journal of Academia and Industrial Research (JAIR). ISSN: 2278-5213.Volume 6, Issue 7. Shahat SA. (2017). Antioxidant and Anticancer activities of yeast grown on commercial media. International Journal of Biological and Chemical sciences. 11(5): 2442-2455. Sivasakthivelan P, Saranraj P, Sivasakthi S. (2014). Produc- tion of bioethanol by Zymomonas mobilis and Saccha- romyces cerevisiae using sunflower head wastes–A comparative study. Int. J. Microb. Res. 5(3): 208-216. Slonimski PP. (2013). Adaptation in microorganisms. Third Symposium of the Society for General Micro- biology, Cambridge University Press, p.76. Tsunatu DY, Atiku KG, Samuel TT, Hamidu BI, Da- hutu, DI. (2017). Production of Bioethanol from Rice Straw Using yeast extracts paptone Dextrose. Nigeri- an Journal of Technology 36(1): 296 – 301. Warringer J, Cubillos FA, Zia A, Gjuvsland A. (2011). Trait Variation in Yeast is Defined by Population His- tory. Plan Genetics. 7: 102-111.