Evaluation of Fibre Enriched and Vitamin - C Fortified Sweetened Probiotic Dahi

Transcription

1 Probiotics in Sustainable Food Production: Current Status and Future Prospects - Probiotic Foods 72 Evaluation of Fibre Enriched and Vitamin - C Fortified Sweetened Probiotic Dahi A. Ramanathan and K. Sivakumar Abstract--- Probiotic dahi fortified with vitamin 50 mg per 100 ml and enriched with oats at 0, 1, 2, 3, 4 percent levels was prepared in the laboratory and were designated as T 1, T2, T3, T4 and T5. A mixed culture consisting of prbiotic organisms viz. Lactobacillus acidophilus, Lactobacillus rhamnosus, Bifidobacterium longum, Bifidobacterium bifidum, Saccharomyces boulardil (Lactobcil Plus) was used for fermentation. The different dahi samples were subjected to organoleptic, chemical and microbiological examination. There was no significant difference in the mean colour and appearance score among control (T1) and dahi samples containing one percent (T2) and two percent (T3) oats powder. However, the mean colour and appearance score was significantly lower (P<0.05) for T4 and T5 samples when compared to others. The mean body and texture score was highest for T3 sample (8.6 ± 0.36) and lowest in T5 sample (7.3 ± 0.30). No significant difference was observed in the body and texture score between T1, T2, and T3 dahi samples. Highest mean flavour score was noted in T2 sample (8.5 ± 0.19). Sample T3 got the highest overall score (8.4 ± 0.21) followed by sample T 1, T2, T4 and T5 with a score of 8.2 ± 0.19, 8.3 ± 0.20, 7.4 ± 0.29 and 7.2 ± 0.25 respectively. Chemical analysis revealed that the fat, protein and total solids content were highest in T5 samples. The mean titrable acidity was also highest in T 5 sample. Microbiological examination revealed highest viable count in control sample when compared to oats added dahi. Coliform growth was observed in none of the samples. Inclusion of oats at two percent level in milk produced dahi of high nutritive value as well as desirable sensory attributes. It is concluded that the maximum level of oats recommended for preparation of fibre enriched dahi is two percent of milk. Keywords--- Fibre Enriched, Vitamin C Fortified, Probiotic Dahi I. INTRODUCTION D AHI is a popular fermented milk product consumed by large sections Indian population from time immemorial. It is consumed either as a part of the daily diet or as a refreshing beverage. Dahi is a nourishing food rich in high quality protein, essential vitamins and minerals. It is also a rich source of calcium and riboflavin. It contains all the nutrients present in milk but in a more easily digestible form. It has been reported that calcium and phosphorus content of dahi are more easily assimilated in the body as compared to milk. Dahi contains more vitamins, which is synthesized by specific lactic acid bacteria. Only vitamin C and fibre are deficient in dahi. In the present study an attempt is made to increase the vitamin C and fibre content of dahi. Antioxidant property of vitamin C prevents cancer, cardiovascular disease and cataracts. The beneficial role of dietary fibre in human nutrition has lead to a growing demand for incorporation of novel fibres into foods. There is little information about fibre fortification in cultured dairy products however various fibers like psyllium, guar gum, gum acacia, oat fiber and soy components can be used. Traditionally dahi is made at home by inoculating boiled and cooled cow or buffalo milk with the left over dahi from the previous day s stock and incubated at room temperature. Homemade dahi culture is dominated by Streptococci and Lactobacilli. Quality and therapeutic value of the dahi can be improved by incorporating specific cultures. Most of the lactic starter cultures used in the preparation of dahi do not adhere and multiply in the intestinal tract. Therefore, they do not survive in the gastro intestinal tract. Contrary to expectations, this type of cultures has no preventive or therapeutic effects. Therefore, selected probiotic bacteria which are capable of thriving in the highly acidic gastric environment and pass in a viable state to the intestinal region A.Ramanathan, Faculty of Agriculture and Animal Husbandry, Gandhigram Rural Institute, Gandhigram, Dindigul District K.Sivakumar, Faculty of Agriculture and Animal Husbandry, Gandhigram Rural Institute, Gandhigram, Dindigul District

2 Probiotics in Sustainable Food Production: Current Status and Future Prospects - Probiotic Foods 73 such as Lactobacillus acidophilus, Lactobacillus rhamnosus, Bifidobacterium longum and Bifidobacterium bifidum is used in the present study to enhance its therapeutic value. Oats contain more soluble fibre than any other grains and are generally regarded as a healthy food. In this context the study was carried out to develop dahi with the nutrients that are absent in milk namely vitamin C and fibre and to find out the optimum level of oats that can be added in milk to produce fbre enriched dahi with desirable sensory attributes. II. MATERIALS AND METHODS Dahi samples were prepared from standardised milk with 4.5 percent fat and 8.5 percent solids-not-fat (SNF) at Dairy Science Laboratory of Faculty of Agriculture and Animal Husbandry, Gandhigram Rural Institute, Gandhigram during the period from January to March The milk was heated to 85 C for 30 minutes. During heating 10 percent sugar and finely ground oats powder was added at different levels. Vitamin C was 500 mg per litre after cooling the milk to 39 to 40 C. The milk was then inoculated with the mixed culture containing probiotic organisms viz. Lactobacillus acidophilus, Lactobacillus rhamnosus, Bifidobacterium longum, Bifidobacterium bifidum, Saccharomyces boulardil (S. lactis) at the rate of two percent. The inoculated milk was distributed in 100 ml plastic cups with suitable lid and incubated at 39 C for 4-6 hours or until a firm coagulum was formed. Table 1: Description of Dahi Samples Prepared with Different Levels of Oats Ingredients T1 T2 T3 T4 T5 Milk (ml) Sugar (g) Oats powder (g) Vitamin C (mg) Inoculum (%) The samples were subjected to chemical analysis to find out the percent acidity, ph, fat, protein, total solids and moisture content as per AOAC (2003) procedure. All the samples were organoleptically evaluated by a panel of experts for acceptability on a scale using 9 points ranging from like extremely to dislike extremely. Microbiological examination of the different samples was also carried out to find out the total bacterial count, coliform and yeast and mould counts. The data obtained were statistically analyzed using the software SPSS (Statistical Package for Social Science) version 10 to find out whether there was any significant difference in various parameters between different dahi samples. III. RESULTS AND DISCUSSION Chemical Parameters Table 2: Mean ± S.E Value of Fat, Protein, Acidity, Moisture, and Total Solids Content of Sweetened Dahi with Different Levels of Oats S.No. Parameter Dahi samples T1 T2 T3 T4 T5 1. Fat (%) 4.5 ± ± ± ± ± Protein (%) 3.5 ± ± ± ± ± Acidity (%) 0.46 ± ± ± ± ± Moisture (%) 76.2± ± ± ± ± Total solids (%) 23.8± ± ± ± ±0.00 From the above table it can be observed that sample T5 had the highest fat content of 4.9 ± 0.60 percent followed by sample T4, T3, T2, and T1. The fat content of the sample showed a gradual increase as the level of

3 Probiotics in Sustainable Food Production: Current Status and Future Prospects - Probiotic Foods 74 oats was increased. The increase in fat content of oats added dahi may be attributed to 6 percent oil present in oats. The fat content of dahi depends on the initial fat content of milk used for curd making or raw material used to prepare the curd and level of volume reduction of milk during boiling (Chowdhury, et al., 2011). The fat percent of plain misti dahi varies from 4.3 to 8.8 percent with an average of 3.8 percent (Gosh and Rajorhia, 1984). The percent titrable acidity showed a gradual increase from T1 to T5 samples as the level of oats increased. However their differences were not statistically significant. The acidity of dahi noted in the present study does not matches the reported value of 0.68 to 0.81 percent (Dey et al., 2011); 1.02 to 1.11 percent (Salunkhe, 2008) and 0.87 to 1.13 percent (Younus et al. 2002). The lower titrable acidity observed in the present study may be due to controlled incubation and postproduction handling and storage at 4 C. Uncontrolled incubation and postproduction handling and storage cause increase in acidity especially during summer. A decreasing trend was noted in the moisture content of the samples starting from T1, to T5. The decrease in moisture content is obviously due to increase in total solids content as the level of oats increased from 1 percent to 4 percent. Conversely the total solid content progressively increased from T1 to T5. Desai et al. (1994) reported that the mean total solids content of plain sweetened dahi was 22.0 percent. In fact, total solids content of dahi depends on different factors such as types of milk used and concentration of sugar (Ghosh and Rajorhia, 1987) as well as the heat treatment (Sarkar et al., 1996 and Ray and Srinivasan, 1972). Ghosh and Rajorhia (1987) observed that total solids content of sweetened market dahi varied from 26.9 to 43.0 percent with an average value of 34.6 percent. This is in conformity with present findings. The higher total solid percentage noted in the present study could be attributed to added sugar and oats powder. Desai et al. (1994) reported that the protein percentage of fresh milk dahi were within the range of 3.7 to 4.3 percent. Hussain et al. (2012) stated that plain dahi contain higher amount of protein than fruit dahi. Addition of increased level of non-fat dry milk increased the protein percentage of dahi (Begum et al. 2011). The protein content of the dahi samples showed gradual increase (Table 2) as the level of oats was increased from 1 to 4 percent. The increase in protein content is due to higher level of protein (17%) in oats than in milk. Table 3: Mean ± S.E Values of Scores of Sensory Evaluation of Different Dahi Samples S.No. Characteristic Score T1 T2 T3 T4 T5 1. Colour and 8.3± ± ± ± ±0.31 appearance 2. Body and texture 8.2± ± ± ± ± Flavour 8.2± ± ± ± ± Sweetness 8.2± ± ± ± ± Consistency 8.5± ± ± ± ± Overall acceptability 8.2± ± ± ± ±0.25 The mean colour and appearance score was highest in T3 sample and lowest in T5. There was no significant difference the mean colour and appearance score among control and dahi samples containing 1 percent (T2) and 2 percent (T3) oats powder. However, the mean colour and appearance score was significantly lower (P<0.05) for T4 and T5 samples. The colour and appearance score showed significant improvement upon addition of oats powder up to 2 percent level. However, it showed declining trend above 2 percent level. The oats does not possess any strong colouring agent. Addition of oats at higher level caused a decrease in the concentration of carotene pigment in the finished product and thus may responsible for lower colouring score. Similarly the body and texture score was highest for T3 sample and lowest in T5 sample. No significant difference was observed in the body and texture score between T1, T2, and T3 dahi samples. However T4 and T5 samples obtained significantly lower texture and body score when compared to other samples. Bhuiyan et al. (2010) also observed improved body and texture score in dahi samples prepared from cow milk added with commercial starch powder at 2 percent level. The increase in body and texture may be attributed to increase in total solid content. However, the decrease in body score at higher oats level may be due to higher crude fibre content of oats. García and McGregor (1997) used seven types of insoluble dietary fibres from five different sources (soy, rice, oat, corn and sugar beet) to fortify sweetened plain yogurt and observed that soy

4 Probiotics in Sustainable Food Production: Current Status and Future Prospects - Probiotic Foods 75 and sugar beet fibres caused a grainy flavour and a gritty texture whereas those made with oat fibre gave the best results in terms of good body and texture and increases in apparent viscosity. Highest mean score of flavour was noted in T2 sample followed by T3, T1, T4 and T5 samples. T1, T2 and T3 samples obtained significantly higher flavour score when compared T4 and T5 samples. However there was no significant difference in flavour score between T4 and T5 samples. Similar trend was noted in sweetness score for various samples of dahi. Begum et al. (2011) reported that addition of vegetable oil and non-fat dry milk with skim milk increased the smell and taste score of reported dahi. The flavour of the product depends on the volatile constituents of milk and also influenced by the quality of the raw milk and fermentation pattern of the product (Chowdhury et al., 2011). The variations in flavour and sweetness score observed in the present study could be attributed to different levels of added oats with a constant sugar level. Sample T3 got the highest overall score (8.4 ± 0.21) followed by sample T1, T2, T4 and T5. Hence, the addition of oats at 2 percent level in milk seems to be good for sweetened dahi. When the concentration of oats increased above 2 percent, the taste, appearance, colour, body and texture score showed a steady decline and the product became less acceptable to consumer. Therefore the addition of oats to increase the nutritive value of dahi may be limited to 2 percent level. Table 4: Total Bacterial Count, Coliform, Yeast and Mould Count of Different Dahi Samples S.No. Characteristics T1 T2 T3 T4 T5 1 Total bacterial 5 x10 5 4x10 5 3x10 5 2x10 5 2x count Coliform Nil Nil Nil Nil Nil 3 Yeast and mould 2x10 2 2x10 2 2x10 2 2x10 2 2x10 2 The total bacterial count was highest in T1 sample (5 x10 5 ) and showed a declining trend with increase in level of oats. The total viable count (log cfu/ml) of dahi in market samples varied from 5.84 to 5.92 (Dey et al., 2011); to (Chowdhuri, et al.,2011). The total viable count in the dahi plays a significant role for establishment of intestinal flora and accounts for its therapeutic property. There was no growth of coliform group of organism in the present study as dahi samples were made in the laboratory under strict hygienic conditions. Yeast growth was observed in all the samples. Yeast growth observed in the present study could be attributed to Saccharomyces boulardil present in the culture used for fermentation. In other situation, presence of yeast was the indication of contamination. These organisms get entry into the product from atmosphere, utensils and human hands under natural conditions. Due to their ability to tolerate acidic condition, yeasts can multiply in dahi and produces gassiness and flavour defects associated with lipolysis of milk fat, if the product is held too long at ambient temperature. However, they grow slowly and their numbers will be low unless the inoculum is transferred from old and yeasty dahi (Gandhi and Natarajan, 2006). REFERENCES [1] AOAC Official Methods of Analysis (17 th ed.). Association of Official Analytical Chemists. Washington, DC, USA. [2] Begum, J, A.Nahar, M.N.Islam and M.M.Rahman, Quality characteristics of dahi prepared from non-fat-dry milk fortified with vegetable oil. Bangladesh Res. Pub. J., 6(1): [3] Bhuiyan, A.I, A.Wadud, A. Nahar and M. Al-Amin, Effects of different approaches on the quality of dahi J. Bangl. Agril. Univ. 8(2): [4] Chowdhury, N.A, K.Paramanik and W.Zaman, Study on the quality assessment of curd (dahi) locally available in Bangladesh market. World J. Food Dairy Sci., 6(1): [5] Desai, S.R, Tono, V.A and Joshi, S.V, 1994: Utilization of different fruits in the manufacture of yogurt. Indian J. Dairy Sci., 47: [6] Dey, S., A. Iqbal, A. Ara and M. H. Rashid, Evaluation of the quality of dahi available in Sylhet Metropolitan City. J. Bangladesh Agril. Univ. 9(1):

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