Influence of Aloe Gel Enrichment on the Physicochemical, Textural and Sensory Characteristics of Dah

R. Pushkala and N. Srividya

Food Technology Division， Department of Home Science， Sri Sathya Sai Institute of Higher Learning， Anantapur， Andhra Pradesh 515001， India

Received: April 15， 2011 / Published: July 20， 2011.

Abstract: Aloe gel， derived from Aloe vera plant is well known for its nutraceutical potential. It is available commercially as a juice with poor sensory quality. The therapeutic benefits of Aloe gel could be extended to food products concomitantly improving its acceptability. Dahi/curd is an Asian fermented dairy product that enjoys tremendous mass appeal. The objective of the present study was to formulate dahi enriched with Aloe gel (AG) as a functional ingredient and to study its effect on the quality of dahi. Plain dahi was prepared by addition of 2.5% skimmed milk powder (SMP) and suitable starter to milk. For the preparation of AG enriched dahi， SMP was replaced by AG at different levels (0.1-0.25%). The products were evaluated for moisture， pH， titrable acidity (TA)， whey syneresis (WS)， total solid content (TS)， water holding capacity (WHC)， total yield (TY)， whiteness index (WI)， and viscosity. Microbial analysis and sensory evaluation were also carried out. Enrichment of dahi with AG was found to improve its quality characteristics by causing a significant reduction in WS and an increase in TA， TS， WHC， TY， WI and viscosity. AG dahi recorded good sensory acceptability. Storage study also indicated AG dahi to perform better in terms of the various parameters studied. The present investigation suggests the feasibility of adding Aloe gel powder as a functional ingredient to dahi to enhance product quality as well as its nutritional and therapeutic potency. It could be commercially exploited as a novel product.

Key words: Aloe gel， dahi， curd， whey syneresis， fermented dairy product， spray dried Aloe gel powder.

1. Introduction

Dahi is a traditional fermented product similar to yoghurt， prepared from cow or buffalo milk or a mixture of them in many of the Asian countries such as India， Bangladesh and Pakistan. Dahi differs from yoghurt in its preparation， involving usually an indigenous， non descriptive starter culture (previously made dahi)， containing LAB and other fermentative organisms. It is a popular item in the Asian meal， and is esteemed for its pleasant and refreshing taste. It is highly nutritious and is also believed to assist digestion and cure intestinal disorders [1].

A clear relation between diet and health is now well established. In this context， functional foods， described as foods claimed to have positive effects on health [2]， are gaining more widespread popularity and acceptance. Advances in medical research， coupled with continuous food technology developments are expected to provide many opportunities for manufacturers to produce cutting-edge functional foods， thus addressing the needs of health conscious consumers. Development of such foods involves fortifying foods with added ingredients that confer health effects on the consumers. In this regard， foods such as curd and yoghurt are being chosen as popular vehicles for the incorporation of therapeutic ingredients.

Dahi， also referred to as curd， is a highly sensitive product. In recent years， several attempts have been made to add ingredients such as probiotics [3]， calcium[4]， fruits and honey [5] among others with the objective of enhancing the dietetic properties of dahi/yoghurt. But， addition of such ingredients has been reported to produce deleterious effects on the product quality in terms of body， consistency and whey syneresis. Altering the composition of curd to make it more nutritious， and at the same time ensuring minimal modification in the sensory and functional properties of the end product， is a major challenge encountered by the dairy industry.

Aloe vera is a popular plant that has been traditionally used for its medicinal and therapeutic properties. It is currently being promoted as a valuable ingredient for the food， pharmaceutical and cosmetic industries [6]. The Aloe gel， obtained from the Aloe vera plant， is the transparent， slippery mucilage produced by the thin-walled tubular cells found in the leaf parenchyma [7]. The polysaccharides present in the Aloe gel， especially the partially acetylated glucomannans， are thought to be responsible for its mucilage-like property. Aloe gel is known to contain diverse compounds which endow it with numerous health benefits [8]. In recognition of its therapeutic potential， Aloe gel is being used in the food industry， essentially in the formulation of health food drinks， manufacture of dairy products and other beverages.

Fresh Aloe gel is however， highly unstable and prone to enzymatic and microbial decomposition [9]. Drying is one of the methods used to reduce degradation and preserve the gel [10]. Among the various dehydration techniques， spray and freeze drying have been recommended to be the most beneficial in retaining the properties of fresh Aloe gel[9， 11]. Among the two， spray drying has been suggested as an efficient and economic option [12]. The present study therefore makes use of spray dried Aloe gel powder for incorporation into curd.

Yoghurt incorporating Aloe gel has been marketed in few countries， but scientific reports with regard to the quality of such products are very limited. In a recent study [13]， yoghurt prepared with Aloe gel juice was reported to exhibit lower levels of macronutrients and poorer textural properties in spite of addition of skim milk powder and gelling agent (sodium alginate). Further 7% sugar has been added which is required to overcome the bitter taste of Aloe gel juice. However， this is not desirable when formulating therapeutic products. In an earlier study Shin et al. [14] determined the effect of adding Aloe gel powder on the product quality of yoghurt. The study reported better viscosity and sensory acceptability of yoghurt with the Aloe gel powder along with gelatin and 4% sugar. In set yoghurt， whey syneresis and related parameters are important product quality indicators which have not been evaluated in these studies. Furthermore， studies on the effect of nutraceutical ingredients on the quality of dahi/curd are very few; with no reports on the effect of Aloe gel enrichment on dahi.

Hence， in the present study， an attempt was made to develop dahi enriched with spray dried powder of Aloe vera gel at different concentrations without the addition of sugar or traditional stabilizers， and to study its effect on the physico-chemical， textural and sensory characteristics of the product. The effect of storage on the quality of the product was also investigated.

Enriching curd with Aloe gel powder could help in achieving a dual purpose， the first one being conferring additional therapeutic and physiological properties to the end product. Secondly， due to the presence of the mucilaginous polysaccharides， it could act as a natural thickener and stabilizer. This could help in providing the desired viscosity and mouth feel to the product thereby preserving the product quality.

2. Materials and Methods

2.1 Preparation of Curd

The milk used in the present study was purchased from the local supermarket (Goodlife brand， fat 3.6%， protein 3.2% and carbohydrate 4.6%). For the preparation of curd， the homogenized milk was heated at 85-90 °C for 5 minutes and cooled to 45 °C. Skimmed milk powder was added at 2.5% level and then inoculated with 10% standard curd starter (Hatsun brand， fat 3.1%， protein 3.3% and carbohydrate 4.4%). Amount of starter was selected based on preliminary experiments. The inoculated milk was incubated at 45 °C till the curd was set.

For the preparation of Aloe gel enriched curd， skimmed milk powder was replaced with spray dried Aloe gel powder (200 X powder， procured from Excel Industries， Hyderabad， A.P.， India) at 0.1%， 0.15%， 0.2% and 0.25% levels.

The control and Aloe gel enriched dahi/curd samples were analyzed for chemical， physical (texture and colour) and sensory characteristics. Setting time and total yield was also determined in fresh samples. Analysis was initially carried out in fresh samples.

2.2 Storage Study

On the basis of the data obtained in fresh samples， dahi enriched with 0.15% AG was selected for storage study. Control and 0.15% AG samples were stored for 7 days at 10 °C， and subsequently analyzed for the various physico-chemical and quality parameters.

2.3 Setting Time

The setting time in hours was recorded from the time of inoculation till the formation of a firm coagulum [5]. 2.4 Total Yield (TY)

Yield of the curd samples was determined in terms of grams of curd obtained from 100 mL of milk. 2.5 Chemical Characteristics

The dahi samples were analysed for pH， titrable acidity， and moisture content. Product pH was determined using digital pH meter (Elico make). Titrable acidity was estimated by standard titration method and expressed as lactic acid equivalent [15]. The moisture content was analyzed as per the standard method of AOAC [15].

2.6 Physical Characteristics

Various physical parameters affecting product quality were analyzed. These include total solid content(TS)， whey syneresis (WS)， water holding capacity(WHC)， and total yield (TY). Instrumental analysis of viscosity and colour was also carried out.

2.6.1 Total Solids

Total solid content was analyzed as per the standard method of AOAC [15].

2.6.2 Whey Syneresis (WS)

Whey syneresis was determined by the modified method given by Amatyakul et al. [16]. A cup of set curd was taken from the refrigerator (10 °C)， weighed and kept at an angle of approximately 45° to allow whey collection at the side of the cup. A needle connected to a syringe was used to siphon the whey from the surface of the sample and the cup of curd was weighed again. The siphon was carried out within 10 s to prevent further leakage from the gel. The syneresis was expressed as quantity (mL) of whey obtained per hundred grams of the curd samples.

2.6.3 Water Holding Capacity (WHC)

The WHC of the samples was determined as per the centrifugation method given by Amatyakul et al. [16]， with slight modifications. A cup of curd was taken from the refrigerator and stirred using a glass rod. Five grams of the stirred curd was taken and transferred to a 15 mL centrifuge tube. The stirred samples were centrifuged at 5000 rpm for 10 minutes and the separated whey was weighed. The water holding capacity was expressed as percentage weight of whey separated from the gel over the initial weight of the curd.

2.6.4 Viscosity

The viscosity of the curd samples was determined using the Brookfield viscometer (Model DV II + Pro). Viscosity was measured (cps) at 20 ± 1 °C， with spindle number 3 at 10 rpm and 30 rpm.

2.6.5 Whiteness Index

The colour of the curd samples was measured in terms of L， a， and b values using the Minolta colour reader CR-10 (Minolta Co. Ltd.， Japan)， which utilizes the CIELAB system. The whiteness index [17] was calculated from these values as per the following Eq. (1):

2.7 Sensory Analysis

Dahi samples were evaluated for acceptability by a group of ten curd consumers. Colour， appearance， aroma， texture and taste of the yoghurts were evaluated using a 5-point hedonic rating scale on the basis of description of each attribute (5-like extremely to 1-dislike extremely). Overall acceptability was determined by calculating the mean total score based on weighted factors assigned to different attributes [18]. The following weighted factors were used: 0.15 for colour and appearance， 0.20 for flavor， 0.30 for texture and 0.35 for taste. The mean total score for each sample was calculated according to the Eq. (2):

(C × 0.15) + (F × 0.20) + (T × 0.30) + (TS × 0.35) (2)

Where， C is the mean score for colour and appearance， F is the mean score for flavor， T is the mean score for body and texture， and TS is the mean score for taste.

The sensory panelists were given guidelines before the evaluation. The samples were evaluated at 10 ±1 °C. The original unopened containers were given to the panelists， so as to reveal the true conditions of the product.

2.8 Statistical Analysis

Experiments were conducted in triplicate trials and the values expressed as mean with standard deviation(SD). Student t-test was utilized to determine significant difference between control and Aloe gel enriched samples for the various parameters in both fresh and stored samples. Statistical significance was set at P < 0.05. Statistical analysis was carried out using MS Excel 2007 software.

3. Results

The results of the study on the fresh dahi samples followed by that of the storage study are given below.

3.1 Setting Time

Setting time observed for the various dahi samples is shown in Table 1. The control sample took the maximum time to set (232 ± 7.5 min). A reduction in setting time was observed with increasing concentrations of Aloe gel powder (AG). Dahi samples with 0.2% and 0.25% AG exhibited the least setting time of 202 ± 7.5 minutes.

3.2 Total Yield

The yield of the samples (Table 1) was found to be higher in AG enriched dahi samples. The maximum yield was observed in 0.25% AG sample (108.2 g/100 mL)， significantly higher than control (104 g/100 mL). Significantly higher yield was also observed in 0.15% and 0.2% AG samples compared to control， though less than that of 0.25% AG.

3.3 Chemical Characteristics

Table 1 shows the results of the effect of addition of AG on pH， titrable acidity and moisture content of the dahi samples.

A decreasing trend was observed with respect to pH， with increasing concentrations of AG. The control sample recorded the highest pH of 5.05， whereas， 0.15%， 0.2% AG and 0.25% AG samples recorded significantly lower pH values. The lowest pH was observed in 0.25% AG dahi (4.76).

The decrease in pH corresponded to a higher acidity in the AG enriched samples with samples having higher concentrations of Aloe gel exhibiting higher acidity. The acidity in the control sample was found to be the lowest (0.61%). A significantly higher (P < 0.05) acidity was observed in AG enriched samples ranging from 0.75% in 0.1% AG to 1.18% in 0.25% AG dahi sample.

The moisture content of the samples recorded significant differences. Increasing concentration of Aloe gel was found to bring about a reduction in the moisture content. The moisture content of control dahi was recorded as 84.2%. No significant differences were observed between the control and 0.1% AG sample， but 0.15%， 0.2 and 0.25% AG samples recorded significantly lower moisture values. 3.4 Physical Characteristics

3.4.1 Total Solid Content

The total solid content of the dahi samples is depicted in Fig. 1.

Significant differences were observed between the control and AG enriched samples with respect to the total solid content. The sample enriched with the highest concentration of AG (0.25%) was found to record the highest TS content of 18.7%. Samples enriched with 0.15% and 0.2% AG recorded similar TS content of 18%， whereas， the lowest content of total solids was recorded in the control sample (15.5%).

3.4.2 Whey Syneresis

Whey syneresis of the dahi samples is depicted in Fig. 2. Whey syneresis decreased with the addition of AG. The sample enriched with 0.25% Aloe gel showed the lowest level of syneresis (0.97 mL)， similar to that of 0.2% AG sample (0.98 mL)， both of which were significantly lower than that of control (1.9 mL). Whey syneresis of 0.1% AG and 0.15% AG samples was also lower than that of control， though in case of 0.1% AG sample， it was not significant.

3.4.3 Water Holding Capacity

Lowest WHC (Table 2) was recorded in control sample (87.7%). Dahi with 0.25% AG exhibited the maximum WHC of 91.8%， followed by 0.2% and 0.1% AG samples (91.5% and 91.4%)， respectively. These values were found to be significantly higher than that of control dahi.

3.4.4 Viscosity

Viscosity (Table 2) of control dahi was found to be 2，518 ± 43 cps recorded at 10 rpm. Aloe gel enrichment had an incremental effect on the viscosity of the dahi samples. Dahi samples with the highest concentration of 0.25% resulted in highest viscosity value of 5，159 ± 59.5 cps. Significantly higher viscosity was observed at both the speeds used for 0.15% AG， 0.2% AG and 0.25% AG dahi samples， compared to control.

3.4.5 Whiteness Index (WI)

The addition of AG at different concentrations and its influence on the L， a， and b values and on whiteness index of curd is shown in Table 3. Control sample recorded a whiteness index of 69.6. A higher whiteness index was observed in the samples enriched with Aloe gel， compared to the control sample. Highest whiteness index of 73.6 was recorded in 0.2% and 0.25% AG samples followed by 0.15% and 0.1% AG samples(72.1 and 71.5)， respectively.

The value “a” is indicative of redness or greenness of the samples and hence did not contribute much in the calculation of WI. “L” value indicates lightness of the samples and positive “b” value indicates yellowness. A higher “L” value with correspondingly lower “b”values in AG enriched samples reflected the WI.

3.5 Sensory Acceptability

Organoleptic properties (appearance， colour， taste， flavor， and body and texture) of the curd samples are presented in Table 4. Significantly higher acceptability score was observed for appearance in all the AG samples compared to control. However， the samples did not differ significantly with respect to colour. With regard to taste， 0.1% AG sample obtained a significantly higher score (4.88) compared to control(4.0). There was a reduction in the taste scores with increase in the level of AG. AG enriched samples obtained higher acceptability scores for flavor (4.33 to 4.55) compared to control (4.08)， though the difference was not significant. A greater acceptability for all the AG dahi samples was observed over the control with regard to body and texture. The values were significantly different from control in all except for 0.1% AG dahi sample.

The total sensory score (Fig. 3)， computed from the various parameters， showed that the least score was obtained by the control sample (4.13)， which was significantly (P < 0.05) lower than all the AG samples， except 0.2% AG sample. The samples with lower AG concentrations， i.e. 0.1% and 0.15% AG samples， recorded the highest scores (4.74 and 4.50)， respectively. Slightly lower scores of 4.43 and 4.47 were obtained for 0.2% and 0.25% AG dahi samples， respectively.

3.6 Storage Study

It can be inferred from the results that dahi with 0.15% AG exhibited good characteristics for maximum of the parameters among the AG enriched samples. Also this level is considered adequate to bring about beneficial physiological effects. Use of Aloe gel as a supplement is recommended in the form of one or two ounces of single strength juice or 150 to 300 mg of 200: 1 gel powder， twice a day [19]. Hence， 0.15% AG dahi was selected for storage studies.

3.6.1 Chemical Characteristics

Table 5 presents the effects of storage upon the pH， titrable acidity and moisture content of control and 0.15% dahi samples.

Upon storage， a drop in pH was observed in both the samples， with a corresponding increase in TA. A significantly lower pH (4.74) and higher acidity(1.37%)， was observed in 0.15% AG sample， over control which recorded a pH and TA of 4.84 and 0.90， respectively， after 7 days of storage.

The moisture content of both the samples showed an increase. The moisture content increased from 84.2% to 85.5% in control， and from 82% to 83% in 0.15% AG sample after 7 days of storage The 0.15% AG sample was characterized by a significantly lower moisture content compared to control after storage.

3.6.2 Physical Characteristics

Fig. 4 and Table 6 show the effect of storage on total solid content (TS) of control and 0.15% AG samples. A decrease in TS from 15.5% to 14% in control， and from 18% to 16% in 0.15%AG sample was observed after 7 days of storage. The TS content remained significantly higher than the control on storage.

The effect of storage on whey syneresis is depicted in Fig. 5 and Table 6. Table 6 also presents the effect of storage on the water holding capacity (WHC) and viscosity of the control and 0.15% AG sample.

A considerable increase in WS and subsequent decrease in WHC was observed in both control and 0.15% AG sample. A significantly higher WS of 2.96 mL and lower WHC of 85.2% were recorded in control sample over the 0.15% AG sample， which showed WS and WHC of 2.3 mL and 89.1%， respectively.

A reduction in viscosity was observed in both the samples upon storage， with the control sample showing a significantly lower viscosity of 2，100 ± 48.1 cps compared to 0.15% AG sample (2，846 ± 59.3 cps).

The whiteness index and L， a， b values of the control and 0.15% AG samples are presented in Table 7. A reduction in whiteness index was observed in both control and 0.15% AG samples， upon storage for 7 days， with the decrease being greater in control sample compared to the AG enriched sample. A significantly higher WI value of 55.1 was recorded in 0.15% AG sample compared to control (53.9).

3.6.3 Sensory Analysis

Table 8 shows the effect of storage on the sensory acceptability of control and AG enriched curd. Significantly higher scores were obtained for 7 day old 0.15% AG sample than control for all the sensory parameters i.e. appearance (4.44 vs. 3.83)， colour (4.55 vs. 4.11)， taste (4.22 vs. 3.53)， flavor (4.11 vs. 3.83)， and for body and texture (4.33 vs. 3.88). The results of the total sensory score (Fig. 6) also showed significantly higher value for 0.15% AG dahi (4.29) compared to control samples (3.75).

4. Discussion

With respect to chemical parameters， a higher acidity and lower pH value was observed for AG enriched curd samples compared to control. This is in agreement to those obtained by Shin et al. [14]. The study reported the pH of control yogurt (prepared using mixed strains of S. thermophilus and L.bulgaricus at 1:1 level) to be 4.80 with an acidity of 1.1%， whereas， Aloe gel enriched yogurt was reported to have a lower pH of 4.33 with an acidity of 1.4%. A study by Ghadge et al. [5] also reported lower pH and higher acidity in yogurt fortified with honey and apple pulp compared to control. Higher acidity in yoghurt samples than curd， generally reported could be due to the use of different starter culture organisms. A similar pH (4.93) to that observed in the present study has been reported in probiotics dahi [3]

Upon storage， a reduction in pH and subsequent increase in acidity was observed in all the samples， with the AG enriched samples showing higher acidity. A study on probiotic dahi by Yadav et al. [3] reported the pH and acidity of fresh dahi to be 4.93 and 0.89， respectively， and 4.73 and 1.27 after 7 days of storage. Another study has also reported a reduced pH and increased acidity in yoghurt samples upon storage [20]. Hassan and Amjad [21] attributed this reduction of pH to the breakdown of lactose to lactic acid， thereby increasing the acidity upon storage. A study by El-Sayed et al. [20] on the addition of polysaccharides like xanthan gum， carageenan， locust bean gum and CMC to yoghurt， reported no marked effect of addition on the pH of the samples， both in the fresh state as well as upon storage. This indicates that Aloe gel polysaccharide unlike the traditional polysaccharides have a stimulative effect on curd metabolic activity.

The TS content of dahi prepared in the present study were found to increase with increasing concentrations of AG. This result is in concurrence with that obtained by Ahmed et al. [22]， who reported increased TS content in yoghurts fortified with defatted wheat germ protein (DWGP)， with higher concentrations showing greater % TS contents.

Whey syneresis， an important parameter for set yoghurt was found to be significantly reduced in AG enriched dahi products， which also exhibited higher total solids. Total solid content has been identified as a major factor affecting whey syneresis [23] and has been found to negatively correlate with whey syneresis in yoghurts [16， 22]. Harwalkar and Kalab [24] and Jaros et al. [25] also reported a reduction in whey separation in set yoghurt when total solids were increased. Similar findings have also been reported by Kogh and Kennedy [26] when different hydrocolloids and stabilizers were added to yoghurt.

Investigations by El-Sayed et al. [20] revealed that addition of xanthan gum to yoghurt at concentration of 0.005% resulted in complete inhibition of syneresis， in fresh as well as in samples stored at 10 °C for 10 days. In the present study， there was a significantly lower WS in 0.15% AG compared to control after storage at 10 °C for 7 days. AG enrichment did not however， inhibit WS completely on storage. Addition of stabilizers such as xanthan gum could be recommended to further inhibit WS on storage.

A significantly lower TS content in the control sample， compared to 0.15% AG samples upon storage， could have resulted in higher WS.

AG enriched samples were also characterized by a significantly higher WHC compared to control both in fresh as well as 7 day stored samples. This could be attributed to lower whey syneresis and higher total solid content of the samples. Yiqiang et al. [27] also reported a correlation between low whey syneresis and high water holding capacity of defatted wheat germ protein fortified samples.

Total yield is estimated after removal of whey. Hence， an increased whey syneresis could have resulted in lower yield of curd in the control sample and conversely a greater yield in AG dahi samples.

AG enriched samples also exhibited significantly higher viscosity compared to control in fresh and stored samples. Similar observation has been reported by Shin et al. [14]， wherein plain yoghurt prepared with mixed strains of S. thermophilus and L. bulgaricus exhibited a lower viscosity of 2，604 cps， whereas similar yoghurt prepared with AG enrichment showed a higher viscosity of 4，100 cps， after 24 h of incubation at 37 °C.

The higher viscosity recorded in the present study in AG dahi samples could be again attributed to the higher TS in these samples. Savello and Dargan [28] also reported yoghurt samples with increased average total solids to exhibit increased gel strength and viscosity. Other studies have also reported that addition of ingredients which increase the dry matter content increase the rheological properties of fermented milk [29， 30].

A reduction in the viscosity was observed in the samples after 7 days refrigerated storage. Yadav et al.[3] also have reported a reduction in viscosity in probiotic dahi on storage for 8 days.

In the present study the lower viscosity observed in the control sample， both in fresh and stored condition， could be attributed to lower acidity of control samples compared to AG dahi. Lower acidity has been postulated to give lesser protein coagulation and formation of soft curd， which could have offered reduced resistance to flow i.e. viscosity [5].

An increase in the instrumental viscosity of the curd samples was observed with increase in AG content in the dahi. This increase was also reflected in the sensory acceptability scores for AG dahi samples.

The whiteness index， computed through instrumental colour analysis was significantly different between the control and AG dahi samples. However， there was no significant difference in the acceptability between the dahi samples in terms of colour. A significantly lower acceptability value was obtained by the control sample for appearance， compared to the AG enriched samples. This could be attributed to the smoother and continuous surface of the set AG dahi compared to control dahi which was characterized by rough surface.

Control dahi recorded lowest score with regard to taste and flavor. This could be due to the lower acidity and insufficient metabolic activity of microorganisms in the sample， resulting in blandness in taste and flavor. Conversely， AG dahi samples with higher acidity had better scores. Among the AG enriched dahi samples， the scores were lower in 0.2% AG and 0.25% AG samples. This could be due to the slightly bitter aftertaste encountered in these samples which could be attributed to the higher concentration of AG used.

The total sensory scores have revealed a significantly higher preference for AG dahi samples. Among the AG samples， 0.2% and 0.25% AG samples， in spite of obtaining higher scores for appearance， colour and consistency， recorded lower preference. This could be due to the lower scores obtained for flavor and taste. Jaworska et al. [31] studied the relative importance of various sensory attributes in the consumer acceptability of yoghurt. Their study revealed flavor (off-flavor) and taste (bitterness) to be critical sensory attributes for consumer acceptance.

Upon storage， a considerable reduction in all the sensory attributes was observed in the case of control sample. On the other hand， the 0.15% AG sample recorded only slight reduction in the sensory attributes， indicating the beneficial role of AG enrichment on maintenance of sensory quality.

5. Conclusion

Enrichment of naturally fermented dahi with spray dried powder of Aloe gel resulted in better product quality in terms of physicochemical， textural and sensory characteristics. The AG dahi also stored well at 10 °C for 7 days. The present investigation demonstrates the feasibility of incorporating Aloe gel to dairy products in particular. This would not only help in improving the product quality characteristics， but would also bestow functional benefits to the product. Further optimization of the product in terms of addition of stabilizers and alternative sweeteners is being currently explored.

Acknowledgments

The first author acknowledges the Junior Research Fellowship (JRF) provided by the University Grants Commission (UGC)， New Delhi， India. The authors thank the founder Chancellor and the management， Sri Sathya Sai Institute of Higher Learning， Andhra Pradesh， India for the research facilities provided.

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