J. Dairying, Foods & H.S., 28 (2) : 95-100, 2009 AGRICULTURAL RESEARCH COMMUNICATION CENTRE www.arccjournals.com / indianjournals.com INFLUENCE OF ADDITION OF GUAVA PULP AND SUGAR ON SENSORY QUALITY OF GUAVA YOGHURT A.P. Patil, K.D. Chavan* and D.N. Bhosale Department of Animal Science and Dairy Science, Mahatma Phule Krishi Vidyapeeth, Rahuri 413 722, India. ABSTRACT Influence of addition of levels of guava pulp and sugar on sensory quality of guava yoghurt was studied with an objective to find out the optimum level of guava pulp that could be incorporated to obtain better quality yoghurt. It was observed that incorporation of guava pulp @ 5 to 15 per cent, after incubation in the stirred form with addition of sugar from 6 to 9 per cent was more acceptable. The guava yoghurt prepared with 5 per cent pulp with 9 per cent sugar was sensorily superior (score 94.6) that of rest of treatments tried in the study. Higher levels of guava pulp adversely affected sensory characteristics of yoghurt. The cost of production was Rs. 26.77 for the most acceptable guava yoghurt. Key words : Guava pulp, Sugar, Guava yoghurt, Sensory quality. INTRODUCTION The production of fermented milk products is increasing rapidly in all the major developing countries of the world. The fermented milk products like yoghurt, cultured butter milk, acidophilus milk, Kefir, etc., are being manufactured in various countries. Dahi, lassi, makhan and chakka are the important fermented milk products of India. Similar popular fermented products produced in different parts of the world are butter milk in Europe, acidophilus milk in Soviet Union, Leben in Egypt, Filbunke and Tattemjolk in Scandinavia, ;Skyr in Iceland, Muzum in Argentina, Cieddu in Itlay Kefir in Balkan countries and Kumiss in Mangolia. Yoghurt is a fermented milk product with custard like consistency. The flavour and texture of yoghurt constitute important aspects of its marketable quality. The characteristics sharp acid flavour with adequate firmness and smooth body and texture without syneresis is essential for a better quality product. Yoghurt has many positive attributes- it is a most refreshing, healthful and flavourful product. * Present address : College of Agriculture, Pune 411 003, India. Yoghurt the magical health food had swept the western world during the last decade. A growing interest towards the consumption of yoghurt due to its higher nutritional and therapeutic properties has been observed throughout the world including countries like Belgium, Switzerland, USA, Italy, Europe and UK but the product has still not gained popularity in India due to lack of characteristic diacetyl flavour (Prasad and Srinivas, 1987). Fruits are considered good source of minerals and vitamins and hence supplementation of yoghurt with fruits will not only improve its flavour but also its overall nutritional quality. Guava (Psidium guajava L.), a native to tropical America, is exceedingly well-known fruit in India, particularly in the plains region of northern India. It is receiving importance as a promising dry land horticulture crop in India. It is 4 th most important local fruit so far as area under cultivation and production in India is concerned. Guava is a rich source of vit. C, pectin and good source of calcium and phosphorus. It is referred as apple of plains due to its high nutritive value with mild flavour. Therefore guava yoghurt will have definite advantage
96 J. DAIRYING, FOODS & H.S. over plain yoghurt. The product will be made mild to suit large cross-section of the Indian population. Further, high pectin content in guava would reduce the amount of stabilizing and gelling agent which are usually added to reduce syneresis. Moreover, much of the need for concentrating milk would be eliminated. Thus use of guava in yoghurt making would not only improve the product quality but would provide one of the outlets for the fruit during peak production period when its market rates are sharply lowered. In view of the above points the present investigation was planned. MATERIAL AND METHODS Milk samples : The composite milk samples of crossbred cows were procured from the Research cum Development project (RCDP) on cattle, MPKV, Rahuri (Table 1). Yoghurt cultures : The freeze dried pure cultures of S thermophilus and L. bulgaricus were procured from the NDRI, Karnal (India). In order to keep these cultures active, they were propagated in skim milk at frequent intervals and preserved in refrigerator. Guava fruits : The normal ripe (greenish to yellow colored) guava fruits of Sardar (Lucknow-49) cultivar were obtained from research farm of Department of Horticulture, MPKV Rahuri, Dist. Ahmednagar and used for experiment. Guava fruits were washed with clean water, skin portion was removed and then they were cut into small pieces. The pieces worked in mixer to obtain pulp. Then pulp was passed through muslin cloth to remove seed material (Table 2). Pectin (manufactured by Sisco Research Laboratory Pvt. Ltd. Bombay India) was used as stabilizer to prevent wheying off in yoghurt. Preliminary trials : Preliminary trials were taken to finalize the form of guava products to be used i.e. pieces, shreds or pulp, stage of addition of fruit, sugar level and pulp level. Yoghurt samples were prepared with 3,6,9,12 and 15 per cent sugar and 5,10,15,20,25 per cent (v/w) fruit pulp levels. On the basis of results of sensory evaluation, 6 and 9 per cent sugar levels and 5, 10, and 15 per cent pulp levels were finalized for final experimental trials. The fruit yoghurt samples were prepared by using standard method described by Sharma and Singh (1981) with suitable modifications. In experimental trials 7 treatment combination with different levels of guava pulp and sugar were studied. Other ingredients viz., SMP 3%, pectin 0.21% were kept uniform in 4% fat cow milk for all treatment combinations. The treatment details were Control : Yoghurt without pulp and (T 0 ) 6 per cent sugar (T 1 ) : Yoghurt with 5% pulp and 6% sugar (T 2 ) : Yoghurt with 5% pulp and 9% sugar P 2 (T 3 ) : Yoghurt with 10% pulp and 6% sugar P 2 (T 4 ) : Yoghurt with 10% pulp and 9% sugar P 3 (T 5 ) : Yoghurt with 15% pulp and 6% sugar P 3 (T 6 ) : Yoghurt with 15% pulp and 9% sugar Cow milk Clarification Standardization Fat 4% Add SMP 3% Stirring Homogenization Addition of sugar (6-9%) and Stabilizer pectin (0.2%) Stirring Pasteurization 85 0 C for 30 min. Cooling to 40 0 C Inoculation with 3 % yoghurt culture (L bulgaricus and S.thermophilus in 1:1 ratio) Incubation at 43 0 C± 1 0 C for 3-4 h Stirring Cooling and quality evaluation (20 0 C) Storage 5-7 0 C Sensory evaluation of fruit yoghurt : Sensory evaluation of yoghurt samples were done by adopting
the procedure described in IS : 6273 (Part Ii), 1972. A 100 point scale suggested by Rangandham and Gupta (1987) was used to adjudge the quality of the yoghurt by a panel of six trained judges. Cost of production of guava yoghurt : The cost of yoghurt preparation was worked out by using the Standard economic procedure (Lal et al., 1980). Statistical analysis : The experiment was laid out in factorial randomised block design. The experiment data was analysed using the methods of Snedecor, and Cochran (1994). RESULTS AND DISCUSSION It was observed that the values for different constituents of cow milk used for these experiments were within the normal range. It was observed that the values for different constituents of guava pulp used for these experiments were within the expected range. Vol. 28, No. 2, 2009 97 Flavour : It is observed that the average score given by the panel of judges for flavour of guava yoghurt samples prepared under different treatments differed significantly (P < 0.05) from that of control samples. Similarly, it differed significantly within the treatments (Table 3). The levels of pulp and sugar caused considerable difference in flavour score of the samples; however, their interactions had nonsignificant effect on flavour. The average flavour score ranged from 39.07 (P 3 ) to 44.30 ( ) for treatment samples while that of control was 40.59. P 2, P 3, and P 3 samples were at par with control while,, P 2 were significantly superior over control sample for flavour characteristics. The maximum score (44.30) for flavour was noticed for yoghurt made using 5 per cent pulp ( ) and 9 per cent sugar ( ), while minimum score (39.07) was received for treatment P 3. Flavour of guava pulp at lower level (5%) was more acceptable Table 1. Chemical composition of milk sample (Means of 4 trials) Milk Per cent ph Fat TS Lactose Acidity (L.A.) Cow 3.95 12.75 4.74 0.15 6.56 (3.55-4.1) (12.26-13.00) (4.49-4.93) (0.14-0.17) (6.10-6.62) Table 2. Chemical composition of guava pulp sample (Mean of 4 trials) TSS Titratable ph Sugar (%) ( 0 Brix) acidity Reducing Non reducing Total (% citric acid) Mean 11.5 1.18 3.7 5.29 1.95 7.24 Range 10-13 1.16-1.21 3.5-4.1 4.86-6.10 1.20-2.80 6.90-7.66 Table 3. Effect of treatment combinations on sensory score of guava yoghurt Treatment Flavour Body and texture Acidity Colour and Containers and Total score (45) (30) (10) appearance (10) closures (5) (100) Control 40.59 29.22 7.14 8.51 5.0 90.45 42.19 26.69 8.35 7.25 5.0 89.48 P 2 44.30 27.93 8.95 7.14 5.0 94.57 P 1 40.20 25.16 6.77 5.94 5.0 83.31 P 2 41.88 26.29 7.89 6.49 5.0 87.56 P S 3 1 39.07 24.35 5.96 4.96 5.0 79.54 P S 3 2 40.01 25.05 6.93 5.65 5.0 82.37 Mean 41.27 25.91 7.47 6.23 5.0 86.14 SE ± 0.243 0.319 0.337 0.301 0.238 CD at 5 % 0.720 0.948 1.001 0.893 0.708 Figures in parenthesis are perfect scores.
98 J. DAIRYING, FOODS & H.S. at both the levels of sugar ( and ). However, 9% level of sugar ( ) was preferred. As the level of guava pulp in yoghurt was increased, strong guava flavour was not liked by the judges. It had deleterious effect on delicate flavour blend of normal yoghurt. Body and texture : From the Table 3 it was revealed that the average score for body and texture attribute of guava yoghurt prepared under each treatment ranged from 24.35 (P 3 ) to 27.93 ( ) while control sample secured maximum as 29.22 out of 30 which was significantly ( P < 0.05) higher than rest of the samples tried. Similarly, it differed significantly within the treatments. The levels of pulp and levels of sugar had significant effect on body and texture (Table 3) however their interaction effect was non-significant. Body and texture score declined as amount of guava pulp increased in yoghurt. It was mainly due to presence of gritty particles in guava pulp even after passing it through muslin cloth. Consequently texture of the product was adversely affected with increase in the level of guava pulp. On the other hand body of the yoghurt was thicker at increased levels of pulp but it could not compensate scores lowered due to undesirable texture. Smoothness of texture increased slightly with increase in sugar level. Wheying off of the product is controlled by using pectin as a stabilizer at the rate of 0.20 per cent during standardization. Acidity : It is observed that the scores (Table 3) given for acidity of yoghurt samples prepared under different treatments ranged from 5.96 (P 3 ) to 8.95 ( ) with mean values of 7.47 out of 10. Acidity score of control sample was 7.14, slightly lower than the mean of all samples (7.47). Because of their inverse relationship interaction effect of these factors on acidity in guava yoghurt was found nonsignificant. The maximum score (8.95) for acidity was noticed for yoghurt made from 5 per cent pulp and 9 per cent guava pulp. In general combinations of higher proportion of guava pulp and lower sugar felt more acidic than the desired and hence these samples (P 2, P 3, P 3 ) scored lower for acidity characteristics. Colour and appearance : The average score for colour and appearance attribute of guava yoghurt prepared under different treatments (Table 3) ranged from 4.96 (P 3 ) to 7.25 ( ) which was considerably lower than the score for control sample (8.51). Addition of guava pulp reduced attractive bright colour and glossy smooth appearance of the product. Within the treatments colour and appearance score of different samples also differed significantly (P < 0.05). From the results given in Table 4 it is seen that increased level of guava pulp, lowered scores while Table 4. Effect of interaction between level of guava pulp and level of sugar on sensory quality of guava yoghurt. Treatment Flavour Body and texture Acidity Colour and Containers and Total score (45) (30) (10) appearance (10) closures (5) (100) 43.24 27.31 8.65 7.19 5.0 92.02 P 2 41.04 25.72 7.33 6.22 5.0 85.43 P 3 39.54 24.70 6.45 5.30 5.0 80.96 SE ± 0.182 0.226 0.223 0.182 5.0 0.468 CD at 5 % 0.550 0.682 0.673 0.548 1.410 40.48 25.40 7.03 6.04 84.11 42.06 26.42 7.92 6.43 88.16 SE ± 0.149 0.185 0.182 0.148 0.382 CD at 5 % 0.449 0.557 0.549 N.S. 1.511 Interaction P x S 41.27 25.91 7.474 6.234 86.14 SE ± 0.258 0.320 0.316 0.257 0.662 CD at 5 % N.S. N.S. N.S. N.S. N.S. Figures in parenthesis are perfect scores.
increased level of sugar, improved colour and appearance scores considerably for this attribute. However, interaction effect of these factors was found non-significant. Control sample of yoghurt was quite attractive, bright, shiny when pulp was added to the extend of 15 per cent (P 3 ), yoghurt showed slightly greenish shade and mealy surface, which lowered their scores for colour and appearance. Slight shadow ness increased with increase in level of pulp. Container and closure : Containers and closures used for storage and presenting the samples of yoghurt to the members of judging Panel were purchased in single lot having same size, shape, colour, etc. They were also kept clean, neat and tidy. Hence all samples received perfect score (5) for this attribute from all judges. Moreover logically levels of guava pulp and sugar used would not affect on score for this parameter. Total sensory score : The average total score for guava yoghurt prepared under different treatment Vol. 28, No. 2, 2009 99 samples ranged from 79.54 (P 3 ) to 94.57 ( ). It is noticed from the results presented in Table 3 that there was significant ( P < 0.05) difference in the total scores for different samples under study. Treated samples differed within themselves as well as from that of control samples. The levels of pulp and levels of sugar had significant effect while their interactions had non-significant effect on total sensory score of guava yoghurt. Higher level of guava pulp led to make its flavour unacceptable might be due to two reasons, first was strong guava flavour had deleterious effect on delicate appealing flavour of plain yoghurt and second was increased acidity in the finished product than the desired. The maximum total score (94.57) was noticed for yoghurt made by addition of 5 per cent pulp and 9 per cent sugar ( ) which was more than 90.45 received for control sample while that of minimum (79.54) was observed in P 3 samples. Total organoleptic score of guava yoghurt samples differed considerably due to levels of pulp and levels of sugar used. But their interaction had Table 5. Cost of production of guava yoghurt (1 kg) under different treatments. (Figures in rupees) Item Treatments Control P 2 P 1 P 2 P S 3 1 P S 3 2 Milk 8.50 8.50 8.50 8.50 8.50 8.50 8.50 (33.66) (32.29) (31.75) (31.04) (30.54) (29.87) (29.41) SMP 3.00 3.00 3.00 3.00 3.00 3.00 3.00 (11.88) (11.39) (11.20) (10.95) (10.77) (10.54) (10.38) Pectin 3.60 3.60 3.60 3.60 3.60 3.60 3.60 (14.25) (13.67) (13.44) (13.15) (12.93) (12.65) (12.45) Sugar 0.90 0.90 1.35 0.90 1.35 0.90 1.35 (3.56) (3.42) (5.04) (3.29) (4.85) (3.16) (4.67) Starter 3.00 3.00 3.00 3.00 3.00 3.00 3.00 culture (11.88) (11.39) (11.20) (10.95) (10.77) (10.54) (10.38) Fruit 0.72 0.72 1.44 1.44 2.16 2.16 pulp (2.73) (2.69) (5.26) (5.17) (7.59) (7.47) Empty 3.00 3.00 3.00 3.00 3.00 3.00 3.00 cups (11.88) (11.39) (11.20) (10.95) (10.77) (10.54) (10.38) Labour 1.54 1.89 1.89 2.23 2.23 2.58 2.58 charges (6.09) (7.18) (7.06) (8.14) (8.01) (9.96) (8.92) Heating 1.20 1.20 1.20 1.20 1.20 1.20 1.20 charges (4.76) (4.56) (4.48) (4.38) (4.31) (4.21) (4.15) Miscella 0.51 0.51 0.51 0.51 0.51 0.51 0.51 neous (2.02) (1.93) (1.90) (1.86) (1.83) (1.79) (1.76) Total 25.25 26.32 26.77 27.38 27.83 28.45 28.90
100 J. DAIRYING, FOODS & H.S. non-significant effect on all sensory characteristics. Sample had good blend of natural flavour of guava and yoghurt, desired body, smooth texture with attractive colour and appearance. So it was judged as the best among all treatments including control samples. Treatment scored very close to that of control sample. Cost of production : The cost of production of 1 kg fruit yoghurt under different treatments was calculated by taking into consideration the prevailing market prices for the various items required (Table 5). The major cost items were milk, pectin, empty cup, starter culture, skim milk powder, fruit pulp and sugar, while the other charges such as labour, heating etc, were worked out on the basis of actual hours of the work performed for the preparation of product. The cost of production of guava yoghurt under different treatment ranged from Rs. 25.25 (control) to Rs. 28.90 (P 3 ). These differences were mainly because of variable levels of guava pulp and sugar used as well as requirements of labour. They were in the increasing order for increased level of pulp and compared to control which was prepared without pulp. Therefore, lowest cost of production (Rs. 25.25) was in the case of control sample prepared with 6 per cent sugar and without guava pulp. The highest production cost of Rs. 28.90 was observed for P 3 yoghurt which was due to the highest levels of both guava pulp (15 % and sugar (9%) used. The overall results of this investigation suggested that the good quality guava yoghurt could be made by addition of 5 per cent guava pulp and 9 per cent sugar ( ). Therefore, if such technology is given to small dairy product processors and to housewives, it will encourage consumption of yoghurt and will gradually replace traditional method of consumption of Dahi (Curd) to certain extent. Those who are reluctant to consume plain dahi or yoghurt may accept fruit yoghurt because of the attractive flavour of the fruits used. REFERENCES IS 6273 (Part-II), (1972). Guide for Sensory Evaluation of Foods (Part-II). Methods and Evaluation Cards. Indian Standards Institution, Manak Bhavan, New Delhi. Lal, M. et al., (1980). Indian Dairyman. 32(6):483. Prasad, D.N. and Srinivas, K. (1987) Cult. Dairy Prod. J. 22(10):12. Cited in Indian Dairyman. 47(4):35. Ranganadham, M. and Gupta, S.K. (1987). Indian Dairyman. 39(10):493. Sharma, D.K. and Singh, J. (1981). Dairy Guide. 37(10):274. Singh, R. (1996). Indian Dairyman. 48(8):19-20. Snedecor, G.W. and Cochran, W.G. (1994). Statistical Methods. 8 th Ed. East-West Press Pvt. Ltd. New Delhi.