Determinação da matéria mineral (Cinzas)

Summary

This lesson covers the process of determining mineral matter (also known as ash) in organic substances. It explains that mineral matter is the inorganic residue left after burning organic material, with the combustion process releasing gases like carbon dioxide and water. The procedure involves using a muffle furnace to incinerate food samples at around 600°C for 3-5 hours. The results allow for the quantification of inorganic elements like calcium and phosphorus, which are vital for calculating other nutrients in animal feed. The importance of using porcelain crucibles and precise laboratory techniques is emphasized for accurate results.

Takeaways

• 😀 Mineral matter (also known as ashes) is the inorganic residue left after burning organic material at high temperatures.
• 😀 The process of determining mineral matter involves burning the sample at approximately 600°C for 3-5 hours in a muffle furnace.
• 😀 The muffle furnace should be equipped with porcelain crucibles, as these are the only containers that can withstand the high temperatures of 600°C.
• 😀 The method requires the food sample to be finely ground to about 1mm and placed into porcelain crucibles for incineration.
• 😀 After burning, the crucibles with the remaining mineral matter are cooled and weighed to determine the amount of inorganic content in the sample.
• 😀 The percentage of mineral matter in the food sample can be calculated by dividing the weight of the mineral matter by the weight of the original sample, then multiplying by 100.
• 😀 The process of calculating organic matter involves subtracting the percentage of mineral matter from 100 to obtain the percentage of organic content in the sample.
• 😀 The knowledge of mineral matter is essential for assessing the content of organic components in food, as it helps estimate the quantity of nutrients like carbohydrates and proteins.
• 😀 This method plays an important role in animal nutrition by helping to understand the mineral composition of food ingredients.
• 😀 For accurate results, the muffle furnace should reach 600°C before starting the burning process, and the samples should be analyzed in a controlled environment to avoid contamination.
• 😀 The method of determining mineral matter provides critical data that influences food formulation and nutritional assessment in various applications, particularly in animal feed.

Q & A

What is mineral matter (ash) in food analysis?

Mineral matter, also known as ash, is the inorganic residue left after the combustion of organic matter in food. It consists of elements like calcium, phosphorus, and other minerals, which remain after volatile substances like carbon dioxide and nitrogen are eliminated during burning.

Why is the ash content important in food analysis?

The ash content is crucial because it represents the mineral content in the food. Understanding the mineral content helps assess the nutritional value of the food, especially the amount of inorganic nutrients like calcium, phosphorus, and other trace minerals.

How is mineral matter determined in a laboratory?

In a laboratory, mineral matter is determined using a muffle furnace, where the food sample is placed in a porcelain crucible and heated to 600°C for 3 to 5 hours. The resulting inorganic residue is the mineral matter, which is then weighed to calculate its percentage in the sample.

What is the role of the porcelain crucible in the ash determination process?

The porcelain crucible is essential because it can withstand the high temperature of 600°C required for the combustion process. Other materials, like glass or aluminum, would melt or break under these temperatures, making porcelain the ideal choice.

What is the temperature and duration for the combustion process in the muffle furnace?

The muffle furnace is set to a temperature of 600°C, and the combustion process lasts for about 3 to 5 hours to ensure complete burning of the organic matter.

How is the percentage of mineral matter calculated?

The percentage of mineral matter is calculated by dividing the weight of the mineral matter (ash) by the initial weight of the sample before combustion. This value is then multiplied by 100 to get the percentage.

How does the determination of mineral matter help in calculating organic matter in food?

Since food is made up of dry matter, which is split into organic and inorganic fractions, knowing the mineral matter (ash) allows us to calculate the organic matter by subtracting the percentage of mineral matter from 100.

What equipment is used in the process of determining mineral matter?

The main equipment used includes a muffle furnace for heating the samples, porcelain crucibles to hold the samples during combustion, a desiccator to cool the crucibles post-incineration, and a drying oven to remove moisture from samples before weighing.

Why is it necessary to grind the sample to 1mm before placing it in the crucible?

Grinding the sample to 1mm ensures uniform combustion and prevents incomplete incineration. A fine, consistent sample size helps achieve accurate results in determining mineral content.

What happens if the wrong type of crucible is used, such as glass or aluminum?

Using the wrong type of crucible, like glass or aluminum, can lead to melting or breaking at high temperatures, compromising the analysis and potentially damaging the equipment. Porcelain crucibles are preferred because they can withstand the 600°C heat without any issues.