Mishtidahi

Mishti dahi or mishti doi is a popular traditional sweetened fermented milk product.The eastern parts of India, especially in West Bengal, Assam, Bihar and Orissa, the sweetened variety of dahi known as Mishti dahi, Lal dahi or Payodhi is quite popular. The product is prepared by the Halwais on a small scale. It is a delicacy of choice during religious festivities and is considered an auspicious item to serve while starting journey or any important work. The product is commonly sold in earthen pots of varying sizes, and served chilled.

i. Composition of Mishti Dahi

Mishti dahi is a fermented milk product, having creamish to light brown colour, firm body, smooth texture, sweet-acidic flavour, and pleasant aroma. As such, there is no prevention of food adulteration (PFA) Act or BIS standards for mishti dahi. In the absence of legal standards, mishti dahi differs in terms of chemical composition as well as sensory attributes. The typical composition of mishti dahi is given in table 2.

Composition of different grades of mishti dahi

The quality of mishti dahi is depend upon the type of milk, level of concentration, and fermentation conditions employed in its manufacture. The effect of levels of starter culture addition on physico chemical and sensory properties of mishti dahi is given in table .

                                                       Influence of amount culture on physico-chemical and sensory

properties of Mishti dahi

ii. Method of Manufacture of Mishti Dahi

i) Traditional method: Traditionally, mishti dahi is prepared from cow or mixed milk. The fresh good quality milk is boiled with a required amount of sugar and partially concentrated by simmering over a low fire. This heating is continued for quite some time during which milk develops a distinctive light cream to light brown caramel colour and flavour. The content is then cooled to ambient temperature and cultured with dahi (lactic) culture). It is then filled into earthen pots of consumer size or bulk size vessels and incubated over night. Normally the curd is set within 12-14 hours. After firm setting of curd, it is transferred to a cool place or stored under refrigeration.

ii) Industrial production: In the organized sector, mishti dahi is manufactured employing improve technological process. A wide range of milk products for sourcing milk solids is used in the production of mishti dahi. For this purpose, milk solids are used from fresh cow/ buffalo milk, cream, skim.Milk powder (SMP), whole milk powder (WMP), evaporated whole milk,sweetened condensed milk and white butter.

The required ingredients are blended in proper proportion, keeping in view the final compositional standard of the product in terms of fat, SNF, and sugar. There is a need to select fresh and good quality ingredients in relation to microbial and sensory quality. The raw material (milk) used for mishti dahi preparation should be fresh, free from off-flavours and has negative clot-on-boiling test.

The most common sweetening agent used in preparation of mishti dahi is cane sugar. Other sweeteners such as corn sugar, corn syrup, and also sugar or maltose can be used as sweetening agent. Some times in preparation of some special varieties of mishti dahi, fresh palm jaggery is used as a sweetener. Commercially cane sugar of high microbiological quality and free from extraneous matter is used as sweetening agent.

Mishti dahi is coloured and flavoured commonly with caramel. Caramel is prepared from heating sugar and it is available commercially in a viscous form (76% TS). Caramel is soluble in water and having a specific gravity of 1.315 to 1.345. Synthetic flavours like caramel, vanilla, cardamom, rose, pineapple, etc may also be used. Fruits and dry fruit, nuts may also be used for developing a wide variety of mishti dahi.

The most critical and important step in the manufacture of the mishti dahi is the selection of appropriate type of starter culture since it affects the flavour, consistency and acidity development in the presence of sugar and caramel at relatively higher TS levels. As such starter culture is regarded as heart of mishti dahi preparation. Mixed strain culture may be used since it yields a superior product and most reliable under variable processing conditions. The optimum activity of the mishti dahi culture is expected in a narrow temperature range of 40-42oC. Normally a good starter culture with 1.0 percent inoculum develops 0.70 percent acidity within 6-8 hours.

Process: The required quantities of milk, cream, skim milk powder and sugar are blended. Caramel is added normally at the rate of 0.10 to 0.12 per cent. The mix is heated to 80o – 900C in a vat or a plate heat exchanger.Various time- temperature combinations have been tried but heating the mix to 85oC for 15 minutes resulted in a highly desirable flavour and textural qualities. After heat treatment, the mix is cooled to 40-42oC either employing heat exchanger or by circulating chilled water in the jacket of vat. The starter culture is added to the mix at the rate of 1.0 percent and thoroughly mixed using stirrer. Thereafter, the mix is filled in samtized cups of required sizes and covered with lids. The cups are properly heat sealed to make them airtight and prevent leakage. These cups are then incubated at 40-42oC for about 6-8 hours till the acidity develops to about 0.70 to 0.80 percent LA. At this acidity the mix will well set and a desired consistency and firmness is attained. After proper setting, these cups are transferred to a cold store of 4-5oC temperature. For long storage, normally the temperature of cold store is maintained at 0oC.

iii) Production of Mishti Dahi from buffalo milk: Fresh buffalo milk is standardized to 3.5% fat and 9.0% SNF, heated to 65oC in a plate heat exchanger and homogenized at a pressure of 56 kg/cm2 (one stage). Milk is concentrated at 1.44 fold in a vacuum evaporator. After adding cane sugar, the milk is heated at 85oC for 5 min to generate cooked flavour. The mix is water cooled to 40oC before inoculation with the mixed culture (LF-40). In some cases, sugar caramel, jaggery and artificial colours are added to impart brown colour. The inoculated mix is aseptically distributed into pre-sterilized polystyrene containers (200 ml) and mechanically transferred to incubation chamber at 40oC. After 7 h of incubation, the product is shifted to cold store maintained at 4oC. During gel formation, milk must remain stationary. In the flow chart (Fig.2),

fermentation is designed as a batch process. In all post fermentation activities,gel should be subjected to a minimum amount of external influences. The influences of varying inocula on physico-chemical and sensory properties of Misti dahi are shown in Table 

Flow diagram for manufacture of Mishti Dahi