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| Author(s): |
Isabela Camargo Gonçalves
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Centro de Energia Nuclear na Agricultura (CENA/STB) |
| Defense date: | 2023-06-23 |
| Examining board members: |
Fabio Rodrigo Piovezani Rocha;
Juliana Naozuka;
Diogo Librandi da Rocha
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| Advisor: | Fabio Rodrigo Piovezani Rocha |
| Abstract | |
Food analysis is essential for product characterization and quality control, by evaluating physicochemical and organoleptic characteristics. In this context, development of fast, more practical, reliable, and environmental friendly analytical procedures is demanded. This MSc dissertation aimed to develop green analytical methods exploiting digital-image photometry for the protein determination in foods and urea in milk. Protein determination was based on ammonia distillation from Kjeldahl digests, detected by the color change of the phenol red acid-base indicator (acceptor solution), using a cell phone camera. A linear response was achieved within 5.050.0 mg L-1 ammonium, equivalent to 0.0030.03 % protein (r = 0.996). Coefficient of variation (n = 10) and limit of detection (99.7 % confidence level) were estimated at 2.3 % and 2 mg kg1 protein, respectively. A sample throughput of 12 h1 was achieved with simultaneous sample processing. Protein amounts determined in foods of animal (milk) and vegetal (beans and lentils) origin agreed with the results of the micro-Kjeldahl reference procedure at the 95 % confidence level. The procedure for the determination of urea in milk exploited the increase of the pH of the medium due to the formation of ammonia in the enzymatic hydrolysis of urea, using a urease solution. The procedure was applied to detection of milk adulterations, which is one of the main targets of food fraud worldwide. The proposed procedure showed a linear response within 2.0-15.0 mg L-1 urea (r = 0.998), with a coefficient of variation (n = 10) and limit of detection (95% confidence level) estimated at 1.6% and 0.5 mg L-1, respectively. Recoveries from 95 and 112% were estimated from samples spiked with urea and results for commercial milk samples achieved by the standard additions method agreed with the reference values (determined by mid-infrared spectroscopy) at the 95% confidence level. The procedure is applicable to whole, semi-skim, and skim milk either pasteurized or processed under ultra-heat treatment (UHT). The proposed analytical methods overcame limitations of conventional procedures, such as difficulties in sample preparation, high cost and analysis time. The proposed analytical alternatives contribute to the evaluation of food quality and safety, being more accessible, consuming low amounts of reagents and solvents and minimizing the amounts of waste generated (AU) | |
| FAPESP's process: | 21/02590-6 - Development of green analytical strategies for the determination of protein and urea in foods |
| Grantee: | Isabela Camargo Gonçalves |
| Support Opportunities: | Scholarships in Brazil - Master |