ANALISIS KADAR AIR - Universitas...
Transcript of ANALISIS KADAR AIR - Universitas...
![Page 1: ANALISIS KADAR AIR - Universitas Brawijayamaharajay.lecture.ub.ac.id/files/2014/02/2_Kadar-Air.pdf2014/02/02 · Kadar Air Metode analisis kadar air yang ideal: •Cepat •Dapat](https://reader034.fdocuments.net/reader034/viewer/2022050903/5fecf0a0045eaf25b850acc0/html5/thumbnails/1.jpg)
ANALISIS KADAR AIR
![Page 2: ANALISIS KADAR AIR - Universitas Brawijayamaharajay.lecture.ub.ac.id/files/2014/02/2_Kadar-Air.pdf2014/02/02 · Kadar Air Metode analisis kadar air yang ideal: •Cepat •Dapat](https://reader034.fdocuments.net/reader034/viewer/2022050903/5fecf0a0045eaf25b850acc0/html5/thumbnails/2.jpg)
AIR
Jumlah melimpah
(70% penyusun kehidupan)
Medium transpor nutrien dan energi kimia
Reaksi enzimatis & metabolisme
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• Air dalam bahan pangan:1. Air bebas :
terdapat dlm ruang antar sel dan pori-pori bahan
2. Air terikat :
air berikatan dengan makromolekul (protein, karbohidrat), berbentuk hidrat dg garam-garam dlm sel (Na2SO4.10H2O)
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Why moisture determination is important ?
• Moisture content affect the stability & quality of foods
• High moisture rapid deterioration
• Ex : mold growth well in grain that contain too much water
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Why moisture determination is important ?
• Moisture content influence the rate of browning of vegetables & fruits
• High moisture rapid browning
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Why moisture determination is important ?
1. Mrp faktor kualitas dlm pengawetan bbrp produk & mempengaruhi stabilitas.
Ex. Dried milks
2. Pengurangan kdr air digunakan utk kenyamanan dlm pengemasan atau pengiriman produk.
Ex. Liquid cane sugar (67% solid)
3. Mengetahui komposisi std bahan pangan.
Ex. Keju cheddar hrs memiliki kdr air ≤ 39%
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Moisture Contents of Foods
Foods Moisture Content (%)
Fluid dairy products :Milk, non fat milk, buttermilk
87-91
Cheeses (cottage) 75
Cream 60-70
Ice cream & sherbet 65
Cheeses (cheddar), mayonaise 40
Butter, margarine 15
Dry milk powder 4
Source : Pomeranz & Meloan (1994)
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Moisture Contents of Foods
Foods Moisture Content (%)
Fresh fruits :Melon 92-94
Citrus 86-89
Various berries 81-90
Ripe guavas 81
Avocado 65
After drying 25
Dried vegetables 7-10
Source : Pomeranz & Meloan (1994)
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Moisture Contents of Foods
Foods Moisture Content (%)
Grain, legumes 10-12
Milled grain (flour) 10-13
Macaroni 9
Breakfast cereal < 4
Baked cereals (pies) 43-59
Bread 35-45
Crackers 5-8
Source : Pomeranz & Meloan (1994)
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Moisture Contents of Foods
Foods Moisture Content (%)
Meat & Fish 50-70
Sausages Varies widely
Poultry meat (geese) 50
Chicken 75
Fresh egg 74
Dries egg 5
Source : Pomeranz & Meloan (1994)
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Moisture Contents of Foods
Foods Moisture Content (%)
Fruit jellies, jam, marmalade
35
honey 20
Various syrup 20-40
White sugar (cane, beet), hard candy, plain chocolate)
1
Source : Pomeranz & Meloan (1994)
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Moisture Contents of Foods
Foods Moisture Content (%)
Sweet potatoes < 69
White potatoes 78
Radhises 93
Green lima beans 67
Cucumber 96
Source : Pomeranz & Meloan (1994)
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Metode Analisis Kadar Air
Metode analisis kadar air yang ideal :
• Cepat
• Dapat diterapkan pada berbagai jenis sampel
• Mudah dilakukan
• Akurasi dan presisi yang tinggi
• Tidak berbahaya
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Metode AnalisisKadar Air
Jenis metode analisis kadar air tergantung dari :
1. Komposisi sampel
2. Perkiraan kadar air sampel
3. Tekstur sampel
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Metode Analisis
• Metode oven kering
• Metode oven vakum
• Metode Distilasi (Azeotropik)
• Metode fisik
• Metode kimia (Karl Fischer)
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Metode oven kering
• Digunakan untuk seluruh hasil pertanian, kecuali yg mengandung senyawa volatil dan mengalami kerusakan komposisi pada pemanasan suhu 100oC, pada tekanan 1 atmosfer.
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• Kelebihan:Sangat sederhana, relatif cepat, dan dpt digunakan utk jumlah sampel yg banyak
• Kekurangan:dekomposisi selama pengeringan, penguapan komponen volatil
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Prinsip:sampel dikeringkan dg oven 100-102oC sampai berat konstan
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Prosedur
• Wadah dikeringkan dlm oven 15 menit
• Dimasukkan desikator, dinginkan, dan timbang
• Timbang sampel ± 2-5 g
• Dikeringkan 3 jam
• Dinginkan dlm desikator dan timbang
• Panaskan lagi dlm oven 30 menit
• Dinginkan dlm desikator dan timbang
• Perlakuan ini diulangi hingga diperoleh berat konstan (selisih penimbangan berturut-turut 0,2 mg)
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Perhitungan
a = berat awal sampel (g)
b = berat konstan sampel (g)
a - b Kadar air (%bb) = x 100 %
a
a - b Kadar air (%bk) = x 100 %
b
b Kadar total padatan (%) = x 100 %
a
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Perhitungan
W1-W2
Kadar air (bb)= ------------ X 100%
W1-W3
W1-W2
Kadar air (bk)=----------- X 100%
W2-W3
Keterangan: W1=berat sampel basah+cawan
W2=berat sampel kering+cawan (konstan)
W3=berat cawan
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Metode Oven Vakum
• Digunakan utk bahan yg mengandung komponen-komponen mudah rusak pd suhu tinggi (bahan yg byk mengandung gula)
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• Kelebihan: pemanasan pd suhu rendah shg
mencegah dekomposisi sampel
pemanasan seragam mencegah case hardening
• Kekurangan: Efisiensi pengeringan rendah
Tidak dapat menganalisis sampel dlmjumlah banyak
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Prinsip
Sampel dikeringkan pd suhu rendah dg tekanan di bawah 1 atmosfer
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Prosedur
• Wadah dikeringkan dlm oven 105oC selama 30 menit
• Dinginkan dlm desikator dan timbang
• Timbang sampel ± 2-5 g dlm wadah yg telah diketahui beratnya
• Keringkan dlm oven vakum selama 6 jam, suhu 60-70 oC dg tekanan ± 25 mmHg
• Lakukan pengeringan sampel hingga diperoleh berat konstan
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Metode Distilasi
• Digunakan utk bahan yg mengandung senyawa volatil (bunga cengkeh, kenanga, bahan jamu tradisional) dan bahan mengandung lemak
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• Kelebihan:
transfer panas efektif dan dan efisien
penghilangan air lbh cepat
atmosfer inert kerusakan oksidasilbh rendah
• Kekurangan :
Jumlah sampel yang dapat dianalisis bersamaan sedikit
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Prinsip
• Air dlm bahan disuling dg menggunakan pelarut organik (toluen, benzena dan xylene).
• BJ air > BJ pelarut organik, shg air ada di lapisan bawah dan bisa dibaca volumenya
• Titik didih air < titik didih pelarut organik
• Pelarut organik tdk dapat bercampur dg air
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Labu Sterling-Bidwell
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Prosedur
• Labu didih diisi sampel (misalnya timbang 3-4 g sampel (W))
• Isi labu dg solvent (toluen, n-hexan)
• Hubungkan labu Sterling-Bidwell dg kondenser dan labu didih
• Lakukan destilasi
• Baca jumlah ml air (V)
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Perhitungan
V = volume air (ml)
W = berat awal sampel (g)
VKadar air = x 100 %
W
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PRACTICE PROBLEMS
You have the following gravimetric results: weight of dried pan and glass disc = 1. 0376 g, weight of pan and liquid sample 4.6274 g, and weight of the pan and dried sample 1.7321 g. What was the moisture content of the sample and what is the percent solids?
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• Sampel awal = (4,6274 – 1,0376) g = 3,5898 g
• Sampel kering = (1,7321 – 1,0376) g = 0,6945 g
• Air yg dihilangkan = (3,5898 – 0,6945) g
= 2,8953 g
Kadar air = (2,8953/3,5898) x 100%
= 80,65%
Total padatan = (0,6945/3,5898) x 100%
= 19,35%
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TERIMA KASIH