Industrial visit to Highland Factory Digana

Group 01

Group 01 E.M.S.Udayakumara-GS/MSc/Food/3622/08

T.L.V.Peiris – GS/MSc/Food/3630/08

K.S.L. Perera - GS/MSc/Food/3630/08

B.A.R. Perera- GS/MSc/Food/3627/08

B.K.K.K. Jinadasa-GS/MSc/Food/3608/08

    

About Milco

Milco (Pvt) Ltd was established in 1956 as “The National Milk Board” under the Ministry of Agriculture. It commenced operations with a single Factory in Colombo donated under the Colombo Plan.

Today it has evolved in to 4 factories which are situated in Colombo, Digana, Ambewala, Pollonaruwa and posses a wide network of milk collection, production and sales centers administrated through out the island and continue to contribute towards the enhancement of the rural economy while providing the much needed nutrition to the entire nation.

Colombo Milk Factory

Colombo Milk Factory is a donation under the “Colombo Plan” by the government of New Zealand to Sri Lanka with the establishment of “National Milk Board” in 1956 and the factory was known as” Colombo Central Dairy ” Initially pasteurized milk in bottles were produced. Later on production was expanded to manufacture of sterilized milk and butter with more donations and investment by other agencies. Next step was the addition of Ice cream and yoghurt to the product range. Subsequent introduction of a modern yoghurt machine helped to increase the supply to the market.

Ambewela Spray Dried Milk Powder Factory

Started in 17th January 1974 with 5600 liters of fresh milk collected at Kotagala Chilling Centre, producing only 100 to 150 Lbs of Milk Powder per day. Today Ambewela spray Dried Milk Powder Factory produces 10-13 Metric Tons from 110,000 Liters of fresh Milk collected from 32 Milk Collecting centers from Passara, Bibile, Bandarawela, Welimada, Haputhale and the surrounding areas. Furthermore in 1989 Butter production too started at this factory and today it produce about 33,000 kilos of Butter.

    

Digana Milk Factory

The Digana Milk Factory was established in 1987 and as at present, manufactures many a number of Highland product range such as yoghurt, cheese, Ice cream, Curd, Sterilized milk, Pasteurized milk etc.Initially the staff strength was 55 and processed 4000 – 5000 liters per day. By now the staff strength is increased to 230 and processes around 11,000 liters per day

Pasteurized milk etc.Initially the staff strength was 55 and processed 4000 – 5000 liters per day. By now the staff strength is increased to 230 and processes around 11,000 liters per day

In 1986, the “National Milk Board” was converted into “Milk Industries of Lanka Company Limited” as a government owned company. After that in 1998 “Kiriya Milk Industries of Lanka (Pvt) Ltd.” took over the administration of “Milk Industries of Lanka Company Limited”. Later in 2000, “Kiriya” was taken back by the government and in 2001 it was named as “Milco (Pvt) Ltd.”, which now stands as a 100 % government owned company.

What is yoghurt?

Yoghurt is a dairy product produced by bacterial fermentation of milk. Fermentation of the milk sugar (lactose) produces lactic acid, which acts on milk protein to give yoghurt its texture and its characteristic tang.

There is evidence of cultured milk products being produced as food for at least 4,500 years. The earliest yoghurts were probably spontaneously fermented by wild bacteria Lactobacillus bulgaricus.

Yoghurt has nutritional benefits beyond those of milk: people who are moderately lactose-intolerant can enjoy yoghurt without ill effects, because the lactose in the milk precursor is converted to lactic acid by the bacterial culture. The reduction of lactose bypasses the affected individuals' need to process the milk sugar themselves.

Yoghurt also has medical uses, in particular for a variety of gastrointestinal conditions, and in preventing antibiotic-associated diarrhea. One study suggests that eating yoghurt containing L. acidophilus helps prevent vulvovaginal candidiasis, though the evidence is not conclusive.

Yoghurt is believed to promote good gum health, possibly because of the probiotic effect of lactic acids present in yoghurt. There is wide range of yoghurt varieties all over the world. The most popular type of yoghurt in Sri Lanka is the “Set Yoghurt”. The Yoghurt produce in Digana factory is a set yoghurt which consist of below nutritional values.

    

Nutrition Information Average Value Per 100g Per one

Cup Fat 3.00g 2.70g Protein 3.50g 3.15g Carbohydrates15.04g 13.53g Vitamin A 10.00mcg 9.00mcg Iron 0.1mg 0.09mg Phosphorous 130mg 4117mg Calcium 140mg 126mg Thiamin 10.00mg 9.00mg Riboflavin 150mcg 135mcg Energy 99.51cal 89.56cal

In addition to the standard set yoghurt they produce several varieties of flavoured yoghurts too such as Banana, Mango and Vanilla.

Production Process

Digana milk factory produces 2 types of yoghurts

1. Sweetened plain yoghurt- Sugar or Colouring are not added

2. Unsweetened yoghurt- sugar and colourings are added.

Flow diagram for yoghurt production

Production of milk by farmers 

Milk collection by chilling centers 

Transportation to factory by insulated trucks 

Storage of chilled milk at 40C 

Pasturization of milk 

(72oC for 15sec)

Storage of pasteurized milk 

Raw materials mixing at 450C 700Lts 

Separation and Standardization of milk 

Cold Storage 4oC‐10 oC for 10 hrs 

Filling 

 4500 cups/h 

Culture inoculation (2%)/ Flavour addition 

Incubation 44oC 2.5‐3.5 hrs 

Cooling to 44oC 

Heat treatment of milk at 80oC for 30 mins 

Homogenization 550C‐150 Kg/Cm2  1000L/h 

    

Milk collection by chilling centers

Milk is collected by from milk farmers by chilling centers and chilled. Due to chilling the temperature is reduced and this leads to lowered enzyme activity of spoilage microorganisms.

Transportation to factory by insulated truck

Due to insulation temperature variations do not occur during transportation. Therefore spoilage of milk during transportation is prevented.

Storage of chilled milk

At factory the milk brought in by insulated trucks are temporarily stored at 4oC until taken to used.

Pasteurization of milk

Stored milk is then pasteurized by HTST (high temperature short time) method by keeping milk at 72 oC for 15 seconds using a plate heat exchanger. This will reduce the microbial load.

Separation and Standardization of milk

The pasteurized milk is then separated into skim milk and cream by centrifugation. After separation standardization is done to achieve the desired fat content for the product. For milk the desired fat content is 3%.

Raw material mixing

Milk, gelatin and sugar are added together and blended at 45oC using an agitator in a mixed tank.

Homogenization

Mixture is homogenized at 55oC using a pressure of 150 Kg/cm2.In addition to thorough mixing Homogenization also prevents creaming and wheying off during incubation and storage. This increases stability and enhance the texture and consistency.

Heat treatment of milk

The mixture which underwent the homogenization is then goes to a heat treatment where the milk is kept at 80oC for 30 minutes. This severe high heat treatment is necessary to produce a relatively sterilize and conductive environment for starter culture. Furthermore this denatures and coagulates whey proteins to enhance the viscosity and texture.

Cooling

    

The above mixture is then cooled down to 44oC. This is the optimum temperature for bacterial starter culture to survive. When mixture achieves this point 2% of freeze dried thermophilic lactic culture and flavours are added to the mix. This particular culture is an imported culture. Then this mixture is thoroughly agitated to ensure a even distribution of the culture throughout the mixture.

Filling

After the above step the mixture is filled into cups at a rate of 4500 cups per hour.

Incubation

Filled cups are then kept at 44oC for 2.5-3.5 hrs for incubation. There will be no agitation and this will facilitate the formation of yoghurt curd or “Coagulum”. Formation of coagulum is formed due conversion of lactose to lactic acid by starter culture bacteria. In this case the lowered PH coagulate the milk proteins. Lactic acid is a product formed due to partial oxidation of lactose sugar under anaerobic conditions by the organism. Enzymes with in the bacterial cells catalyze the lactic acid formation reaction.

Cold storage

Due lactic acid formation the PH value of the mixture goes down. When it comes to iso electric point of casein (PH 4.6-4.7) is approached, it sent to cold storage where yoghurt is stored at 4oC -10oC for about 10 hours to hinder the fermentation, chemical, microbiological and physical degradation.

Enzyme activity related to the production of yoghurt

Yogurt is a product obtained through milk fermentation with a specific yogurt starter culture consisting of a mixture of two species of lactic acid bacteria (LAB), Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus .The main roles of this mixed starter in the production of yogurt are (i) acidification through the conversion of lactose into lactic acid, (ii) creation of the viscous texture by the production of exopolysaccharides, and (iii) development of the typical yogurt flavor The typical yogurt flavor is caused by lactic acid, which imparts an acidic and refreshing taste, and a mixture of various carbonyl compounds like acetone, diacetyl, and acetaldehyde, the latter of which is considered the major flavor component .The relatively high concentration of acetaldehyde (in the range of 5 to 21 mg/liter) found in yogurt must be due to a low utilization rate of this metabolite since the yogurt bacteria lack the main enzyme for acetaldehyde conversion into ethanol, alcohol dehydrogenase . The production of acetaldehyde by LAB seems to be strain dependent. L. delbrueckii subsp. bulgaricus has been reported by some authors to be a greater acetaldehyde producer than S.

    

thermophilus, whereas other authors have reported the contrary.Although it is presently unclear what the major pathway for acetaldehyde production by LAB is, several metabolic pathways have been shown to lead to its formation and it is possible that more than one metabolic pathway operate simultaneously. During yogurt fermentation, acetaldehyde can be produced directly from lactose metabolism as a result of pyruvate decarboxylation. It can be produced (i) directly via pyruvate decarboxylase or pyruvate oxidase or (ii) indirectly through the formation of the intermediate acetyl coenzyme A by pyruvate dehydrogenase or pyruvate formate lyase. Furthermore, acetaldehyde can be formed by the activity of deoxyriboaldolase, which degrades thymidine into acetaldehyde and glyceraldehyde-3-phosphate. Finally, while several amino acids can be converted into acetaldehyde via pyruvate as a metabolic intermediate, threonine can be directly converted into acetaldehyde and glycine by the activity of threonine aldolase (TA)

Overview of different metabolic pathways in LAB that could lead to acetaldehyde formation Acetyl CoA, acetyl Co-enzyme A.

In the yogurt bacterium S. thermophilus, the only enzyme with TA activity (interconversion of threonine into acetaldehyde and glycine) seems to be the serine hydroxymethyltransferase

    

(SHMT; EC 2.1.2.1). This is an important enzyme involved not only in the formation of glycine and serine but also in the turnover of folate in all organisms.However, the role of TA in acetaldehyde formation in mixed yogurt cultures is still not fully understood. The aim of this work was to investigate the role and importance of SHMT in the production of acetaldehyde by S. thermophilus. It was observed that the main pathway for acetaldehyde formation in this microorganism is through the activity of SHMT since the inactivation of the encoding glyA gene led to the almost complete abolition of TA activity. This result indicates the absence of an alternative pathway for acetaldehyde production and thus establishes the importance of SHMT in the production of this key aroma compound. Overexpression of the glyA gene showed an increase in TA activity and in acetaldehyde and folic acid formation. These results indicate that, in S. thermophilus, SHMT with its TA activity constitutes the main pathway for acetaldehyde formation under our experimental conditions. These findings could be used to control and improve acetaldehyde production in fermented (dairy) products by using S. thermophilus as starter culture. They also allow the selection of natural S. thermophilus variants with improved flavor-forming characteristics and the improvement of acetaldehyde formation through the metabolic engineering of SHMT.

Quality Assurance

Food base industries are engaged in introducing different kind of food products to meet the customer satisfaction. In this regard, important facts are assuring quality and safety of the food while processing and delivering. Therefore, it is very necessary to ensure that food product is safe for human consumption, and it has the necessary quality characteristics expected by the customers. In this connection, the most acceptable recognized management system with regard to the quality and safety of food in the world are identified as ISO 22000: 2005. ISO 22000 is a integrated management system with management system and the Food Safety System named as HACCP (Hazard Analysis Critical Control Point) In this HACCP system it is aimed at preventing hazards at the earliest possible points in the food chain.

Ambewela spray dried milk factory was awarded with ISO 22000 Food Safety Management System Certificate in the year 2007, by Sri Lanka Standards Institution. Following benefits were obtained after certification of this award.

Quality control methods used at Digana milk factory

    

1. In collecting centers the quality of milk is tested by using lactometers

2. The milk which is transported to factory from chilling centers are checked for below quality parameter

i.Microbial load

ii. Adulterants

iii. Fat

iv. Total soluble solids

3. Yoghurt cups are randomly collected and checked for microbial quality after incubation.

4. CIP (clean in place) system is in used to clan the equipments.

5. Standard GMP and GHP methods are in practice to avoid cross contamination.