vi
PENGARUH SUHU DAN LAMA PENYIMPANAN TERHADAP
KADAR NITRAT DAN NITRIT DALAM BROKOLI
(Brassica oleracea. L)
ABSTRAK
Sayuran merupakan sumber utama paparan nitrat dalam makanan. Nitrat terbentuk secara alami di dalam tumbuhan melalui daur nitrogen. Nitrat memiliki efek racun yang rendah bagi tubuh manusia, namun nitrat dapat berubah menjadi nitrit dimana nitrit memiliki tingkat berbahaya yang lebih tinggi dibanding nitrat. Akumulasi nitrat dan nitrit didalam tubuh dapat menyebabkan kanker usus serta methaemoglobinaemia pada bayi berumur kurang dari 6 bulan. Faktor suhu dan lama penyimpanan dapat menyebabkan perubahan kadar nitrat dan nitrit. Tujuan penelitian ini adalah untuk mengetahui pengaruh suhu dan lama penyimpanan terhadap kadar nitrat dan nitrit pada brokoli.
Dalam penelitian ini sampel yang dianalisis adalah brokoli yang berasal dari pasar induk lau cih, Medan tuntungan. Sampel disimpan selama 0 jam, 6 jam, 12 jam, 24 jam, 30 jam dan 36 jam pada dua suhu penyimpanan yaitu suhu lemari pendingin (± 10°C) dan suhu kamar (± 30°C). Sampel dihaluskan, ditimbang, dipanaskan dan dilakukan metode analisis kualitatif dan kuantitatif. Analisis kualitatif nitrit dilakukan dengan menggunakan pereaksi asam sulfanilat dan N-(1-naftil) etilendiamin dihidroklorida dan dengan menggunakan pereaksi KMnO4 dan
H2SO4 (p). Analisis kualitatif nitrat dilakukan dengan menggunakan pereaksi
Serbuk Zn dan NaOH(e) dan dengan menggunakan pereaksi KI dan Asam Asetat. Penentuan kadar nitrit dilakukan secara spektrofotometri sinar tampak dengan menggunakan pereaksi asam sulfanilat dan pereaksi N-(1-naftil) etilendiamin dihidroklorida pada panjang gelombang maksimum 540 nm. Penentuan kadar nitrat dilakukan dengan cara mereduksi nitrat terlebih dahulu menjadi nitrit dengan menggunakan serbuk Zn kemudian diukur menggunakan spektrofotometri sinar tampak.
Hasil Penelitian menunjukan bahwa pada suhu kamar selama penyimpanan 0 jam sampai 36 jam, kadar nitrit meningkat dari kadar awal 1,53 mg/kg menjadi 1,75 mg/kg dan kadar nitrat dari penyimpanan 0 jam sampai 36 jam meningkat dari kadar awal 64,19 mg/kg menjadi 154,51 mg/kg. kadar nitrit suhu lemari pendingin selama penyimpanan 0 jam sampai 36 jam meningkat dari kadar awal 1,53 mg/kg menjadi 2,09 mg/kg dan kadar nitrat dari penyimpanan 0 jam sampai 36 jam meningkat dari kadar awal 64,19 mg/kg menjadi 113,06 mg/kg.
Kata Kunci : Brokoli, Nitrat, Nitrit, Spektrofotometri Sinar Tampak, Suhu dan lama penyimpanan
vii
THE EFFECT OF TEMPERATURE AND STORAGE TIME
AGAINTS NITRATE AND NITRITE IN
BROCCOLI (Brassica oleracea. L)
ABSTRACT
Vegetables are the major source of nitrates in human intake. Nitrate occurs naturally in plant by nitrogen cycle. Nitrate has low level of acute toxicity, but it can be transformed into nitrite, which has much higher acute toxicity. Accumulation of nitrate and nitrite in the body can increase risk of colon cancer and methaemoglobinaemia in infants under 6 months of age. Temperature and storage time might changes in nitrate and nitrite level in vegetable. The purpose of this research is to investigate the effect of temperature and storage time againts nitrate and nitrite level in broccoli.
The sample were analyzed was broccoli which were obtained from Lau cih market, Medan Tuntungan. Samples were stored for 0 hours, 6 hours, 12 hours, 24 hours, 30 hours and 36 hours in separated storage condition, that is refrigerated (± 10° C) and room temperature (± 30° C). Sample which has been mashed, weighed and heated were subjected to qualitative and quantitative analysis. Qualitative analysis of nitrite was performed by using sulfanilic acid and N- (1-naphthyl) ethylenediamine dihydrochloride and using KMnO4 and concentrated H2SO4.
Qualitative analysis of nitrate was performed using Zn powder and NaOH 0.2N solution and by using KI and Acetic Acid. Determination of nitrite level was conducted by using visible spectrophotometry method at maximum wavelength of 540 nm with addition of sulfanilic acid and N-(1-naphthyl) ethylenediamine dihydrochloride prior to analysis. Determination level of nitrate was conducted by reducing nitrate to nitrite first by using Zn powder, and then determination level of nitrite were performed as in the step of determining the reduced nitrite level.
The results show that nitrite level of broccoli stored in room temperature during 0 to 36 hours of storage increased from 1.53 mg / kg to 1.75 mg / kg and nitrate levels during 0 to 36 hours storage increased from 64.19 mg / kg to 154.51 mg / kg. Nitrite levels of broccoli storage from refrigerator temperature during 0 to 36 hours of storage increased from 1.53 mg / kg to 2.09 mg / kg and nitrate levels increased from 64.19 mg / kg to 113.06 mg / kg.
Key Words: Broccoli, Nitrate, Nitrite, Visible Spectrophotometry, temperature and storage time
