Physicochemical and sensory profile of spiced yogurt as affected by ginger supplementation

ABSTRACT Food fortification processes are used to improve the functional and dietary characteristics of the final product. The basic aim of the current study was to evaluate the ginger (Zingiber officinalis, Roscoe) fortification in yogurt and to improve its functionality. For this purpose, ginger at different concentrations (0%, 0.5%, 1%, 1.5%, and 2%) was added to yogurt. The results showed a significant influence (p < .05) on physicochemical and phenolic content as well as on the sensory parameters of fortified yogurt. Moreover, the addition of 1.5% ginger powder in yogurt resulted in the best results for protein (3.30%), moisture (79.16%), and water-holding capacity (39.85%), respectively. Furthermore, the total phenolic contents were also higher in T3 (19.91 μg GAE/g); however, the total plate count tends to decrease ranging from 3.94 to 3.58 log CFU/g in different treatments. The results of the sensorial assessment revealed T3 was appreciated the most among all treatments.


Introduction
Dairy products are consumed by almost 6 billion people in the world as a part of their diet because of their composition and are beneficial during adolescence and childhood.The high contents of some micronutrients, protein, and fat (phosphorus, and calcium these two are micronutrients, how about to mention some vitamins) are present in milk and other dairy products, and these are useful to promote neurologic, muscular, and skeletal development.As most of the world's population is lactose intolerant and is unable to gain the benefits of dairy products several fermented dairy products which contain reduced amount of lactose are produced and are famous all over the world. [1]Many diseases can be prevented by high milk diets such as childhood obesity, cardiovascular disease, and type 2 diabetes (need references here) and it also helps to maintain bone health which reduces the risk of osteoporosis. [2]ogurt is a famous fermented dairy food that can be prepared by the action of two essential lactic acid bacteria (Lactobacillus bulgaricus and Streptococcus thermophilus).It is reported that Streptococcus sp.helps to enhance the nutritional worth and edibility of fermented dairy food.Efforts have also been made to fortify yogurt with ingredients that are obtained from natural sources as a new method for yogurt production, which may impart additional.In most cases, these food fortification processes are done to improve the functional and nutritional characteristics of the final food product. [3,4]inger (Zingiber officinalis Roscoe) belongs to the Zingiberaceae family, one of the widely used herbs and spices in large varieties of food and beverages across the world.It is also known to have therapeutic properties as it contains many biologically active compounds which contribute to health benefits. [5]Ginger has revealed good antimicrobial consequences against both gram-negative and positive bacteria.It may help to regulate blood pressure in humans by stimulating the physiological systems. [6]Since ancient times in Asian, Arabic, and Indian herbal ethnic rhizome or stem of this plant has been used as a medication.The ginger rhizome can be used in the form of flavoring in tea, a fresh paste of ginger, preserved slices, and a dried powder. [7]Herbal yogurts (a new category of yogurt that has been fermented from milk in the presence of herbs or bioactive plant materials) have been shown to improve antioxidant activity and high compounds of bioactive peptides which may lead to novel series of yogurts with potential health properties to the customer.Many studies on ginger spiced yogurt have shown its ability to increase the shelf-life of yogurt because of its antimicrobial properties and enhanced antioxidant properties.With increasing concentration, ginger powder has also been shown to improve the nutritive value of yogurt as opposed to ginger extract. [8]Ginger is available in many forms, but here, we have focused on the use of its powder form.The current study was carried out to prepare ginger-fortified yogurt and to evaluate the physicochemical and sensory properties of fortified yogurt.

Procurement of raw material
Raw cow milk was collected from the local dairy farm in Faisalabad.Commercial lactic acid bacterial culture (LAB) was obtained from Dairy Technology laboratory of the National Institute of Food Science and Technology (NIFSAT), University of Agriculture Faisalabad.Ginger was purchased from Jhang Bazar Market Faisalabad.The study was performed at different laboratories of NIFSAT and the Department of Food Science Government College University Faisalabad, Pakistan.

Ginger powder preparation
For the preparation of ginger powder, ginger was washed to remove contaminants, peeled, and sliced into small pieces 2-3 mm thick followed by drying in an oven (40°C for 5-6 h).The Dried ginger was grounded to powder form and stored in food-grade polythene bags at room temperature until required for further analysis.

Preparation of ginger-fortified yogurt
Yogurt was prepared by following the method of Imran [9] with some modifications.The milk was pasteurized in a hot water bath at the temperature of 85-90°C for 5 min.The pasteurized milk was cooled down immediately to the temperature of yogurt starter culture inoculation, which is 39°C.Then, the yogurt starter culture comprising Streptococcus thermophilus and Lactobacillus bulgaricus in a ratio of 1:1 was added (2.5% w/v).After a brief manual stirring of milk ginger powder was added at four different concentrations (i.e.0%, 0.5%, 1%, 1.5%, and 2%), which were labeled as T 0 , T 1 , T 2 , T 3 , and T 4 , respectively.The inoculated milk was then incubated using an incubator (Memmert incubator, Germany) at 37 ± 2°C for 3 h in separate storage boxes.The yogurt formed was left to cool in the refrigerator (4°C) for 3-4 h all yogurt samples were stored at 4-6°C for physicochemical and sensorial evaluation.

Physicochemical analysis of ginger-fortified yogurt
Ginger-fortified yogurt was evaluated by various analyses on every seventh day of storage.The AOAC method was used to determine the pH, titratable acidity, moisture content, protein contents, total soluble contents, fat contents, ash contents, syneresis rate, and water-holding capacity (WHC). [10]

Total phenolic contents
Total phenolic contents were assessed by the method described by Shori. [11]

Microbiological analysis
Yeast and mold count and total plate count were checked according to standard methods for dairy product examination as described by Bakry. [4]Microbial analyses of yogurt samples were performed at 0, 7, and 14 days at 4 ± 1°C of cold storage.One gram of well-stirred yogurt was diluted in 9 ml sterile peptone water (0.1%), yielding a 10 −1 dilution.Serial dilutions were subsequently prepared and bacteria were counted, applying the standard plate count method.

Sensorial evaluation
Sensorial evaluation of the samples was done using a 9-point hedonic scale by a set of trained panels (1-dislike extremely; 9-liked extremely) at the National Institute of Food Science and Technology according to the method by Bouaziz. [12]The product was evaluated at different refrigerated storage periods for its overall acceptance texture, color, aroma, appearance, taste, and flavor.

Statistical analysis
All data were interpreted with respect to statistical analysis following ANOVA under CRD design according to the method as described by the study [13] For the application of statistical parameters, Statistics 8.1 (Analytical Software, Tallahassee, FI, USA) software was utilized.

Titratable acidity and pH of fortified yogurt
The mean results for ginger-fortified yogurt are shown in Figure 1(a), and it illustrates that acidity fluctuated significantly (p < .05) in all treatments throughout the storage and manifested an increasing trend with respect to storage days.Minimum titratable acidity was observed at 0 days and maximum at the end 14 th day of storage.The maximum acidity was observed for T 4 followed by T 3 and the lowest titratable acidity was found in T 0 .The findings were in agreement with Widayat who concluded that at the end of the fermentation period, the titratable acidity of red ginger in yogurt increased from 1.3% to 3.1% as recorded in the current study. [14]The total quantity of lactic acid formed contributed largely to the acidity of that product.During fermentation, lactose is transformed into lactic acid by the action of inoculated bacteria which contributes to .Effect of ginger fortification (0%, 0.5%, 1%, 1.5%, and 2%) on titrable acidity of yogurt during storage intervals (0, 7 th 14 th day) compared with control (To).Each bar represents the mean value for fortified yogurt treatment.(b) Effect of ginger fortification (0%, 0.5%, 1%, 1.5%, and 2%) on the pH of yogurt during storage intervals (0, 7 th 14 th day) compared with control (To).Each bar represents the mean value for fortified yogurt treatment.(c) Effect of ginger fortification (0%, 0.5%, 1%, 1.5%, and 2%) on the moisture content (%) of yogurt during storage intervals (0, 7 th 14 th day) compared with control (To).Each bar represents the mean value for fortified yogurt treatment.(d) Effect of ginger fortification (0%, 0.5%, 1%, 1.5%, and 2%) on total soluble solids (%) of yogurt during storage intervals (0, 7 th 14 th day) compared with control (To).Each bar represents the mean value for fortified yogurt treatment.(e) Effect of ginger fortification (0%, 0.5%, 1%, 1.5%, and 2%) on the protein content (%) of yogurt during storage intervals (0, 7 th 14 th day) compared with control (To).Each bar represents the mean value for fortified yogurt treatment.(f) Effect of ginger fortification (0%, 0.5%, 1%, 1.5%, and 2%) on the water holding capacity (%) of yogurt during storage intervals (0, 7 th 14 th day) compared with control (To).Each bar represents the mean value for fortified yogurt treatment.To (control treatment), T 1 (yogurt fortified with 0.5% ginger powder), T 2 (yogurt fortified with 1% ginger powder), T 3 (yogurt fortified with 1.5% ginger powder), and T 4 (yogurt fortified with 2% ginger powder).
increased acidity in milk products.During the storage period, the acidity of dairy foods generally increases because of the continued bacterial metabolic activity present in the product. [15]he mean results for ginger-fortified yogurt (Figure 1(b)) showed that the pH of yogurts declined significantly (p < .05)with increasing amount of ginger added during refrigerated storage.Initially, the highest pH value was recorded in T 0 (4.67) with T 4 showing the least pH value (4.41).After 7 days of refrigerated storage, ginger fortified yogurt was found highest in T 0 (4.42) and lowest in T 4 (4.15).The pH of T 1 , T 2 , and T 3 were 4.47, 4.23, and 4.24, respectively.On the 14 th day, the results of T 0 , T 1 , T 2 , T 3 , and T 4 treatment were 4.28, 4.24, 4.14, 4.12, and 4.07, respectively.The findings are in agreement with the study that showed the modification in the pH of yogurt supplemented with spices such as cinnamon, nutmeg, and cardamom displayed a similar decrease in pH during storage days as recorded in the present study. [16]Also, the pH of foods containing probiotics decreased during storage due to the presence of bacteria therein in either encapsulated (references) or free (references) form, as reported by Afzaal. [17]This reduction in pH is attributed to the increased metabolic activity of an increasingly higher bacteria population with time which uses carbohydrates in the product as an energy source resulting in the accumulation of organic acids as by-products. [18]

Moisture content
The moisture content of yogurt showed a significant (p < .05)decline trend that can be noted in Figure 1(c).The maximum decline in moisture was noticed by the 14 th day.Initial moisture content was in the range of 80-85%.After 14 days, values for moisture content were reduced to 82.39%, 80.41%, 79.63%, 79.16%, and 77.40% for To, T 1 , T 2 T 3, and T 4 , respectively.A study also concluded that the moisture in yogurt decreased at the end of (2 weeks) storage days to 83.05%. [19]The addition of fruit pulp, herbs, and spices decreased the moisture content of yogurt and caused an increase in the total solids of yogurt, this might be due to the presence of pectin in herbs which bound the water. [20]As the consistency of yogurt depends upon the total solids and moisture content, higher total solid and lower moisture percentages as a result of ginger addition increase might be increased due to the high level of pectin in ginger and the firmness of yogurt. [19]The decreased moisture content of yogurt Effect of ginger fortification (0%, 0.5%, 1%, 1.5% and 2%) on the Total phenolic content (μg GAE/g) of yogurt during storage intervals (0, 7 th 14 th day) compared with control (To).Each line represents mean value for fortified yogurt treatment.To (control treatment), T 1 (yogurt fortified with 0.5% ginger powder), T 2 (yogurt fortified with 1% ginger powder), T 3 (yogurt fortified with 1.5% ginger powder) and T 4 (yogurt fortified with 2% ginger powder).
during storage days as observed in the present studies can be attributed to the evaporation of moisture under refrigerated conditions. [20]tal soluble solids TSS of ginger-fortified yogurt is shown in Figure 1(d).TSS varied from 11.90% to 13.30% in all different treatments and throughout the storage periods.The highest value of TSS was found in T 4 (12.69%)followed by T 3 (12.30%),whereas T 0 (11.90%) had the lowest TSS in the study also reported that of the addition of sour cherry pulp into yogurt resulted in an increasing TSS from 13.64% (into 21.25% by the end of the fermentation period). [21]In general, TSS is reduced with the progression of refrigerated storage which is considered not dependent on the storage conditions.Hence, TSS in yogurt depends entirely on the nature and amount of the herbs and fruits added.

Protein contents
Based on protein analysis, red ginger used for fermentation had no protein that causes red ginger extract to make yogurt and had no significant impact on protein content.A significant (p < .05)increasing trend was observed for ginger-fortified yogurt (Figure 1(e)).During storage, the highest value of protein contents was found in T 3 (3.30%)and the lowest value of protein contents was found in T 0 (2.69%).As the concentration of ginger powder and storage period increase protein contents of different treatments also increased, which showed that there was a direct relation between spices addition and protein contents.This is in agreement with the study which reported that the addition of garlic may increase protein content by up to 4.19%. [22]rotein has a great impact on the structure and nutritional value of yogurt. [22]In fact, the practice of adding varied plant materials into yogurt can effectively enhance the protein, fat, and total solids contents with the potential benefits of altering the physicochemical properties of yogurt. [23]ter holding capacity (WHC) increased significantly from 34.84% to 41.54% in all treatments during storage (see Figure 1(f)).WHC was noted highest in T 3 (39.85%),whereas the lowest WHC value was recorded in T 0 (34.86%).WHC of T 1 , T 2 , and T 4 treatments were 37.26%, 38.58%, and 37.71%, respectively.As the storage period increased WHC was also increased, which implies a direct relation between ginger addition and water-holding capacity.The study investigated the impact of different herbs on yogurt in the storage of 28 days, and they also found that the WHC of fortified yogurt was increased to 41.25%. [24]The increased total solids due to the addition of plant materials c can act as hydrocolloids which are responsible for the increase in WHC. [25]

Total phenolic content
The total phenolic content as a result of fortification of yogurt with ginger increased significantly (p < .05)from 14.64 to 19.91 μg GAE/g Figure 2Figure 2.
The highest value of total phenolic contents was found in T 3 (19.91μg GAE/g) followed by T 4 (18.32 μg GAE/g), whereas the lowest value of total phenolics was found in T 0 (14.64 μg GAE/g).Extended refrigerated storage to 14 days resulted in the highest total phenolic content compared to day 0 and day 7 of storage.Total phenolic contents in T 1 , and T 2 treatments were 15.34 μg GAE/g and 16.24 μg GAE/g, respectively.These findings as well as that of the study are expected since milk proteins proteolysis during refrigerated storage release amino acids with phenolic side chains, chiefly tyrosine contributing to the total phenolic content measured. [26]Moreover, bacterial breakdown of phenolic contents in spicefortified yogurt and the construction of new phenolic acids in acidification might also result in the added increase in phenolic groups. [27]The study observed a decrease in TPC and suggested that this could be due to the proteolysis of milk proteins which may release amino acids with phenolic side chains, mainly tyrosine.Furthermore, microbial metabolism of phenolic compounds in ginger powder yogurt treatments as well as the production of new phenolic acids during acidification may result in an increase in phenolic groups.

Yeast and mold count
Yeast and Mold Counts (TYMC) are used to identify the amount of fungal development on plant material and allow for reorganization of viable yeast and mold species existed.The number of fungi is described as the number of colonies forming units (CFUs).Mold and yeast counts are known as important indicators of the quality and shelf life of yogurt.Both were undetected in the control yogurt control sample as well as other treatment samples until the beginning of 2 nd week of storage.Mold and yeast counts ranging from log 0.9-1.06log CFU/g in yogurt fortified with ginger powder (Table 1) which indicates a significant response (p < .05).It was detected at the beginning of 3 rd week of storage.
Fortified spices in yogurt and found that no unwanted microbes were present throughout the storage days. [28]The study also found that there was no yeast or mold present in fortified yogurt during the first 2 weeks of storage. [29]However, yeast or mold was detected only after the 3 rd week with values ranging from log 3.82 log Cfu/g in the control to log 2.66 log Cfu/g in fortified yogurt with spices.In general, the addition of plant materials is able to suppress the growth of mold and yeast in fortified yogurt samples and this can be attributed to the inhibitory effects of bioactive compounds with anti-microbial properties present in spices reported. [4]

Total plate count
The mean results for total plate count (TPC) for ginger-fortified yogurt were shown in Table 1.TPC was found to fluctuate from 3.94 to 3.58 log CFU/g during storage.TPC was significantly (p < .05)different and showed a rising trend from 2.78 ± 0.01 at the 0 day to 6.97 ± 0.04 on 7 th day.The increase in TPC at the beginning of the storage period followed by a decline at the end of fermentation time as observed in the present as well as previous study can be explained by the increase in acidity of the product and formation of components like diacetyl, carbon dioxide, and ethanol formation in fermentation media. [29,30]From the results, it can be suggested that the addition of ginger in yogurt inhibits the growth of microbes due to the presence of natural antimicrobial compounds in it.However, a significant (p < .05)increase in the total plate count as well as mold count can be observed in the control treatment.

Sensory evaluation of ginger-fortified yogurt
The mean results obtained for sensory evaluation of ginger-fortified yogurt are shown in Table 2. Sensory evaluation was carried out according to a 9-point hedonic scale with a significant difference (p < .05).The last scored yogurt treatment was the control treatment (T 0 ) and T 1 (0.5% ginger powder).T 3 treatment received the highest score implicating it was liked extremely by all the evaluators.The effect of plant additives on the decrease in yogurt color during refrigerated storage (using mint) was similar to ginger-fortified yogurt in the present study. [31]The study also investigated the flavor of yogurt during 14 days of storage and found that scores of flavors of fortified yogurt decreased at the end of cold storage as in current research. [32]The findings completely agreed with the study who investigated the texture of yogurt during cold storage and found that scores for texture. [14]

Conclusion
Fortification of ginger powder in yogurt enhances its physicochemical, sensory profile, and total polyphenolic content of yogurt.The use of natural ingredients like ginger gave an acceptable flavor, color, odor, and texture to yogurt and helps to increase shelf life.The addition of ginger not only gives a unique flavor to yogurt but also increases the health benefits of yogurt by increasing anti-oxidant and total viable cell.The use of ginger powder in yogurt enhances the sensorial features of yogurt but no substantial impact was recorded in the overall acceptability of the yogurt.