Production and Characterization of Starch Nanocrystal

Abstract

In this study, it is aimed to produce high crystallinity nanocrystals from starch which is a very interesting raw material in recent years as a natural and renewable resource in nano material production. For this purpose wheat starch was acid hydrolyzed using different amount of acid (starch:H2SO4 ratio; 1:2 and 1:4) at 50C temperature for 5 days. After hydrolysis, samples were dialyzed to remove impurities and freze-dried. Native wheat starch and nanocrystals were characterized by using scanning electron microscope (SEM); X-Ray diffaction spectroscopy (XRD) and Fourier Transform Infrared Spectrometer (FT-IR) in terms of size, crystallinity and structure, respectively. Native wheat starch was also characterized as control and the effect of hydrolysis on size, crystalinity and structure. According toSEM images, it can be observed that the size of native wheat starch varied between 5-10 µm. It was observed that the size of starch granule decreased considerably as a result of acid hydrolysis. The size of wheat starch granule decreased below the 50 nm due to the hydrolysis procedure. While native starch granules were observed as independent granules, starch nanocrystals located as aggregates. According to the XRD patterns, it was observed that the starch nanocrystals obtained by acid hydrolysis gave the A-type X-ray diffraction pattern, which is the typical X-ray diffraction pattern of wheat. While there was no difference between X-ray diffraction patterns between native wheat starch and starch nanocrystals in terms of structure, there was a considerable difference between crystallinity index values of these samples. The starch nanocrystals produced by acid hydrolysis had higher crystallinity index values when compared with its corresponding which had 42.2% crystallinity. The crystallinity index value of starch nanocrystals produced by using low acid ratio (1:2) was 57.3%, whereas the crystallinity index value of starch nanocrystalline produced by using higher acid ratio (1:4) was determined as 68.5%. According to FT-IR results, it was observed that starch nanocrystals have the same structure as native wheat starch.

Keywords

• Wheat starch
• starch nanocrystals
• crystallinity
• XRD
• SEM
• FT-IR

Nişasta Nanokristali Üretimi ve Karakterizasyonu

Abstract

Bu çalışmada nano malzeme üretimi konusunda doğal ve yenilenebilir bir kaynak olarak son yıllarda oldukça ilgi çeken bir hammadde olan nişastadan yüksek kristaliniteye sahip nanokristal üretimi hedeflenmiştir. Bu amaçla buğday nişastası farklı oranlarda H2SO4 (1:2 ve 1:4 nişasta:asit) ile beş gün boyunca 50℃ sıcaklıkta hidroliz edilmiştir. Hidroliz sonrasında örnekler diyalize tabi tutularak safsızlıklar giderilmiş, liyofilize edilerek kurutulmuştur. Elde edilen nişasta nanokristalleri taramalı elektron mikroskobu (SEM) kullanılarak boyut; X-Işını Kırınım Spektroskopisi (XRD) kullanılarak yapı ve kristalinite; Fourier dönüşümlü kızılötesi spektrometresi (FT-IR) kullanılarak yapı açısından karakterize edilmiştir. Doğal haldeki buğday nişastası da aynı şekilde karakterize edilmiş ve hidroliz işleminin yapı, boyut ve kristalinite üzerine etkisi incelenmiştir. SEM görüntüleri incelendiğinde buğday nişastasının boyutlarının 5-10 µm arasında değişim gösterdiği belirlenmiştir. Asit hidrolizi sonucunda ise nişasta boyutunun oldukça azaldığı ve 50 nm’nin altına düştüğü gözlenmiştir. Doğal haldeki buğday nişastası birbirinden bağımsız granüller halinde iken nişasta nanokristalleri kümeleşmiş halde görüntülenmiştir. XRD desenleri incelendiğinde asit hidrolizi ile elde edilen nişasta nanokristallerin buğdayın tipik X-ışını kırınım deseni olan A-tipi X-ışını kırınım desenini verdiği gözlenmiştir. X-ışını kırınım desenleri yapı açısından incelendiğinde işlem görmemiş doğal haldeki buğday nişastası ile nişasta nanokristallerin arasında fark görülmese de, bu örneklerin kristalinite indeks değerlerinin farklı olduğu belirlenmiştir. Doğal haldeki buğday nişastasının kristalinite indeks değeri %42,2 olarak belirlenmişken, asit hidrolizi ile üretilen nişasta nanokristallerinin kristalinite indeks değerleri daha yüksek bulunmuştur. Düşük oranda asit kullanılarak üretilen nişasta nanokristalinin (1:2) kristalinite indeks değeri %57,3 iken daha yüksek oranda kullanılarak üretilen nişasta nanokristalininin (1:4) kristalinite indeks değeri %68,5 olarak belirlenmiştir. FT-IR sonuçlarına göre ise nişasta nanokristallerin doğal buğday nişastası ile aynı yapıya sahip olduğu gözlemlenmiştir.

Keywords

• Buğday nişastası
• Nişasta nanokristali
• Kristalinite
• SEM
• FT-IR
• XRD

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