Introduction pH fresh milk (between 6.7 and 6.5) Slightly acidic Value lower 6.5 (considerable acid taken place) Value higher 6.7 (mastitis infection) Litmus paper : indicate pH (test milk activity) pH measurement : acceptance test for milk Measuring milk acidity is important to determine milk quality
Advantages data logger :- Can collect data independently of a computer- Mistake of misread the data will not happen- Graphs & tables produce automatically Disadvantages data logger :- Cost of purchasing- If break down, some data will be lost / not recorded- If malfunction, cost needed to repair is higher- Drawing skills become weaker
Problem statementAhmad bought milk from the nearby shop. He drank in a little amount and then left it on the table. He forgot to store the milk into the refrigerator.The next day, he drank the leftover milk. But, he found out that the taste was totally different than yesterday. The milk tasted sour. He wonders what happened to the milk when it is left and exposed.
Why does the taste of the milk changes as it is exposed? Is the sour milk acidic or basic? If the milk is acidic or basic, what is the pH value?
Equipment required:1. Data logger Electronic device that records data over time Automatically collect data in wide range of time Accurate data on the environment conditions being monitored can be obtained.Data logger Data logger compartments
2. pH sensor To measure pH of milk. Provide automatic data collection. Can measure pH from range 0 to 14.3. Milk
Methodology 1. The milk from bottle is pour into a glass. 2. The milk is then allow to reach the room temperature without cooking and re- pasteurising it. 3. The pH probe is plug into the data logger socket. 4. The pH probe is inserted into the milk. 5. Run the software. 6. All data are recorded and displayed in graph form.
Data logger connected to PCpH probe inserted into milk
The reduction in pH can be seen shortly after starting the experiment. When exposed to air, bacteria will start to grow rapidly contributing to the sourness of the milk. After few days, we can see that the pH starting to decrease to a lower value. Milk contains lactose, but at the same time milk also contained bacteria.
Some bacteria work efficiently in warm conditions and causes milk become sour. pasteurized milk undergo series of steps, bacteria are not completely killed in this process. The left bacteria will gradually reproduce and turns the milk into sour.
The main reason why milk turns sour is because the lactose in the milk is converted to lactic acid. As the acid level increases, the pH levels drops. If milk is exposed, the bacteria in the milk will start to produce and forms gases and chemicals which change its smell, taste, texture.
If we incubate UHT milk in a closed arrangement :- Provide higher bactericide effect- Decrease contamination- Bacteria activity decrease- Milk become stable (taste) If we consume contaminated food :- Cause by microorganisms- Cause disease (food borne illnesses)- Common symptoms : diarrhea, vomit, fever, jaundice
If we consume food contained higher acidity :- Our stomach is an acidic place- When we eating, acid secreted into the stomach (digestion)- Secretion acid + food (higher acidity) very acidity- Cause : sour tummy / sour stomach, acid reflux
Reduction in pH is not constant over entire the experiment, From the graph, the gradient significantly increases half way. As the time increases, the pH is reduced. Means that acidity increases. Milk begins to sour. Milk’s sugar acids (by bacteria)
The extent of change in pH during experiment, The pH of milk in first day is 6.75. In contrast, the pH of milk in fourth day is 4.8. So, the change in pH is = 6.75 – 4.8 = 1.95
Many of the cheese are produced in food industry. Cheese can be produced by using milk and soy milk
How curd or cheese can be produced by own at home or in kitchen? Explain.
Yogurt is one of the Malaysian’s choices.Yogurts come from milk that may help prevent from Osteoporosis.
A milk+ vinegar/ lemon juice + heat A milk + acid (produced by bacteria) + heat A milk + rennet + heat Milk fat & protein separate from the liquid cheese
Need acidifiers to convert Milk sugar lactic acid Acidifiers = lemon juice / bacterial special starter cultures purchased from a cheese-making suppliers. Bacteria are added to acidify the milk. So, rennet will work.
Milk is fermented + lactose-loving bacteria = yogurt. The lactose-loving bacteria consume lactose - produce lactic acid Lactic acid responsible for tart flavor + thickening (acting on the casein protein in the milk.)
Different compositions lactic-acid bacteria = vary in yogurt-like products. US’s yogurt, made with lactobacillus bulgaricus and streptococcus thermophilus. The milk needs to be fairly warm between 105 and 115 degrees in order to the organisms in this culture to function.
1. Repeating the experiment using unpasteurized and Ultra Heat treated milk,2. Keeping the container of milk at different temperature whether in fridge or an incubator,3. Using different milk source such as goat’s milk, cow’s milk and soy milk in experiment, and4. Using different milk product such as Dutch Lady, Marigold, Everyday, Nestle and Farmhouse Milk (F&N).
Educational data logger motivates students & increase student’s interest in learning process. In future, data logger can be used in school in Malaysia and also educational institutions. Make students more familiar with technology instrument / computer. The data that viewable make students more easily to analyse the data.