Meyve dokularında niteliksel ölçüm yapabilen elle tutulabilir spektroskopik donanım tasarımı ve gerçeklemesi
Design and implementation of a hand-held devi̇ce to spectroscopically assess fruit quality
Yazar: ALİ SARIKAŞ
Danışman: PROF. DR. FATMA İNCİ ÇİLESİZ
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Elektronik ve Haberleşme Mühendisliği Ana Bilim Dalı / Biyomedikal Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2014
Konu: Biyoteknoloji = Biotechnology ; Elektrik ve Elektronik Mühendisliği = Electrical and Electronics Engineering

Özet:
Gıda endüstrisinde, gıdanın güvenilirliği ve kalitesi, doğrudan insan sağlığını ilgilendirdiğinden önemli bir konudur. Hızlı ve tahribat yapmadan algılama yapan spektroskopi tekniği, meyve ve sebzelerin toplama öncesi, toplama sırası ve toplama sonrasında büyümesi ve gelişimini çözümlemede çok önemli bir teknik olmuştur. Spektroskopi tekniği ile meyvelerin dokusunun yapısal değişimi, klorofil pigmentlerinin sayısal ölçümü gibi iç ögeler ile coğrafik yapı, hava ve toprak koşulları, meyvelerin topraktan beslenme durumu gibi dış etmenler hakkında üreticiye hızlı bir geri bildirim sağlanması, üreticinin meyvenin gelişimi için daha erken girişimde bulunmasını da sağlamaktadır.
Literatür incelemesi sonucunda gıda endüstrisinin ürünleri olan günlük tüketilen besinler, süt, meyve, sebze, mısır, yağ, et, balık yağı, meyve suları, zeytinyağı ve daha birçok gıda ürününün UV, VIS ve NIR spektroskopisi kullanılarak nitelik çözümlemelerinin yapıldığı görülmüştür. Yapılan ön laboratuvar çalışmaları sonucunda 280-2500nm dalga boylarında meyve dokusu ile ışık arasındaki etkileşim izlenmiş ve yansıma bantları gözlenmiştir. Tez çalışmasında meyvenin olgunluğunun belirlenmesinde 3 kriter incelenmiştir: 1) Meyvenin renk durumu için kabuğundaki pigmentler, 2) Meyvenin etlenme durumu için hücre yapısı, 3) Meyvenin sulanma durumu için suyun soğurma bantları.
Işığın dokuyla etkileşimi temelde 4 türlüdür: 1) Yansıma ve kırılma, 2) Geçiş, 3)Saçılma ve 4) Soğurulma. Bu olaylar dokudan dokuya ve dalgaboyuna göre farklılık gösterir. Işıma boyunca ışık doku etkileşim mekanizması dokunun fiziksel özellikleriyle belirlenir. Dokunun fiziksel özellikleri optik, ısıl ve mekanik özelliklerdir. Bu özellikler genel olarak soğurma katsayısı, saçılma katsayısı, anizotropi faktörü, ısıl iletim, ısı kapasitesi ve mekanik dayanıklıktır. Bu deneysel çalışmada sıcaklık ölçümü yapılmadığından sadece dokunun soğurma, saçılma ve anizotropi tanımlarından bahsedilmiştir. Işık doku etkileşimlerinde dokuda meydana gelen değişiklikler soğurma ve saçılma olaylarının bir sonucudur. Dokunun saçıcı özelliği, fotonların doku içindeki dağılımı açısından önemlidir. VIS ve NIR bölgesinde (400-1200 nm) saçılma dokuda baskındır. Meyve dokusundaki soğurgan moleküller genel olarak su, porphyrin (klorofiller), flavin, glukoz, yağ asitleri ve aminoasitlerdir. Biyolojik dokular %60-80 kadar su içerdiginden NIR ve IR bölgelerinde soğurma genelde su molekülü tarafından yapılır. Tez çalışmasında yapılan çözümlemelerde dokunun yapısından kaynaklanan bu soğurma ve saçılma olayları sonucu yüzeyden küresel yansıma değerlerinin değerlendirilmesi temel alınmıştır. Tez çalışmasının ilk bölümlerinde saçılma ve soğurma olayları kuantum teorisine göre yeterli bilgi verecek şekilde açıklanmıştır.
Tez çalışmasında spektrofotometre ile yapılan çözümleme sonuçlarına göre aynı çözümlemeyi yapabilecek bir el tipi cihazın prototipi geliştirilmiştir. VIS ve NIR bölgesinin çözümlemelerini yapabilmek için  RGB LED ve IR LED ışık kaynakları kullanılmıştır. Mikrodenetleyici, sayısal/analog ve analog/sayısal dönüştürücüler ve uygun detektörler kullanılarak tasarlanan cihazın, ölçümlerde optimum sonuçları verebilmesi kalibrasyon ayarları yapılarak ve uygun yazılım ile desteklenerek sağlanmış, verimli sonuçlar elde edildiği gözlenmiştir.

Abstract:
In the food industry, food safety and quality are still performed as an important issue all over the world, which are directly related to people's health and social progress. Consumers are gradually looking for quality seals and trust marks on food products, and expect manufacturers and retailers to provide products of high quality. All of these factors have underlined the need for reliable techniques to evaluate food quality. Considering the demands in practice, it is necessary to develop a fast and efficient method such as NIRS technology to evaluate internal quality of food.
A rapid nondestructive sensing technique could be very helpful to monitor and to manage different working steps directly in horticultural production, at harvest as well as in fruit and vegetable preharvest and postharvest processing. Because of the fast response, the inﬂuence of different external factors like geographical site, weather and soil conditions, nutrition status, etc. can be assessed early-on during plant development and the producer may take appropriate measures at an earlier date than conventional.
Visual spectroscopy (VIS) covers the wavelength range from 400 to 750 nm. Within this range, several important plant pigment groups (chlorophyll, anthocyanins, and carotenoids) can be detected. Each pigment absorbs light within characteristic wavelength bands. The degree of light absorption in each of these wavelength bands correlates with the relative pigment content of the cell tissue included in the measurement. The Beer–Lambert law shows the relation between wavelength-speciﬁc light absorption and the concentration of absorbing molecules in a sample. NIR spectroscopy utilizes the spectral range from 780 to 2500 nm (12,500-4,000   cm-1) and provides much more complex structural information related to the vibration behavior of combinations of bonds. The record of NIR region of the electromagnetic spectrum involves the response of the molecular bonds O-H, C-H, C-O and N-H. These bonds are subject to vibrational energy changes when irradiated by NIR frequencies, and two vibration patterns exist in these bonds including stretch vibration and bent vibration. These can be measured with NIR spectrophotometer.
In the literature, quality of dairy products such as cheese and milk, fruit and vegetables, corn seed, fatty acids, meat, fish oils, fruit juices, olive oils, and processed food was analysed using UVS, VIS, and NIRS techniques. After our review, light-fruit canopy interactions observed were in the wavelength range from 280 to 2500nm. The spectral signature of plant canopy in VIS and NIR wavelength range indicates sensitively the seasonal development and particularly the effect of stress conditions on chlorophyll and water content. Reﬂectance from plant foliage is largely controlled by plant pigments in the spectral region between 0.4 and 0.7 µm, by internal leaf structure between 0.75 and 1.0 µm, and by foliar moisture content between 1.1 and 2.5 µm. 
In principle, four eﬀects exist which may interfere with its undisturbed propagation:
•	reﬂection and refraction,
•	transmission,
•	absorption,
•	scattering.
These effects vary different tissues and as a function of wavelengths. During irradiation, interaction mechanisms are determined by physical properties of tissues. These properties are generally optical, thermal and mechanical. Interactions are influenced by absorption coefficient, scattering coefficient, anisotropy, thermal propagation, heat capacity, and mechanical strength. Only the absorption, scattering and anisotropy effects of tissue are mentioned in this study because no heat generation. In light-tissue interactions mechanism, absorption and scattering events cause changes in tissue structure. Scattering function of a tissue is important for photon propagation. Scattering effect is a dominating factor in VIS and NIR region (400-1200 nm). Water, phorphryn (chlorophyll), flavonol, glucose, fatty acids and aminoacids are absorber molecules (chromophores) in fruit cell structures. Because the water content is 60-80% in biological tissues, water molecules cause the absorption in NIR and IR regions in general. In this study, diffuse reflection was evaluated/measured. In the first part of the thesis, scattering and absorption processes are explained in a clear and concise manner, according to quantum theory.
The aim of this study is to develop a hand held electronic device that can do measurements like spectrophotometers. To manage this, first, light sources were chosen. RGB LED and IR LED were used to analyse the wavelength range of VIS and NIR regions. Second, to detect the reflected signal from fruit canopy, highly sensitive photodiodes (Silicon PIN Photodiodes) were used. These photodiodes' spectral responsivity covers 190-1250 nm wavelength range and λ0.5 values are between 400 and 1100 nm wavelength range. Reflected light signal is an analog signal and this signal must be first filtered and amplified, then converted to digital to evaluate by a microcontroller. This converting process is performed by analog to digital converters (ADC). The microcontroller used in this study has an embedded 10-bit ADC modul. Because of the inefficiency of programming memory, a microSD memory card was used in addition. All reference values and measurement values were processed and recorded in a text file (.txt extensive file). This file can be easily read by a PC. To drive the RGB LED, 3 digital-to-analog converters (DACs) controlled by microcontroller were used. 10-bit digital signals were applied to the relative inputs of DACs. Conventional calibration models were tested and a novel method was developed. Thanks leading to this new method, acquired spectroscopic data can provide useful information to prediction of maturity and optimum harvest date. Fruit maturity cases were displayed on a 128×64 bit resolution graphical LCD (GLCD). Measurement results can be monitored over the graphical LCD display installed on the developed hand-held device and the corresponding results can be obtained as percentage. Specific percentage intervals are shown on the display for three different states of the fruit. By considering the results of the measurements, it becomes possible to determine the maturity state of the fruit (immature, half-mature, mature) as well as the suitable harvesting time of the fruit according to its maturity. 
In such a device only using UV and NIR light sources degree of aging of human skin, wound / burn healing, can be measured. Also available for this device with the optical fiber probe design more precise measurements can be made from the tissue surface. Using specific wavelengths and powerful light sources can also be more thick-skinned fruits maturity analysis. By changing the light source mentioned in the introduction of the thesis can be made from fruits other qualitative measures. This device provides a record of the reference number of the desired flexible software architecture can be measured by the thousands of species of fruit (~150,000 fruit type) allows. Measuring period (~5 seconds) is too short a period of time in resolution consequently faster measurement provides more instances. Analysis of the material to the thin film coating of composite materials, as well as to improve the strength properties of the compounds employed in the qualitative analysis of the optical properties may also be undertaken.
This manuscript consist of six chapters:
1.Introduction
2.Light-Tissue Interactions
3.VIS-NIR Spectroscopy
4.Materials
5.Methods
6.Results and Discussion