Dissertation
DEVELOPING A SENSOR TO DETECT VOLATILE COMPOUNDS IN MILK TO MONITOR SHELF LIFE
Doctor of Philosophy (PhD), Washington State University
01/2017
Handle:
https://hdl.handle.net/2376/117927
Abstract
There is great interest from food industries, and food safety controlling bodies to develop accurate, cost effective, rapid, and reliable methods of evaluating the shelf life and quality of food. This dissertation is focused on developing a Silicon dioxide (SiO2) based sensor capable of detecting VOCs to monitor shelf life. In this study, pasteurized milk (3.9% fat) was stored at 5,7,10,13,13,15 and 19 (±1°C) up to the end of shelf life. Microbial counts including aerobic plate, psychrotrophic bacteria, and Bacillus spp. were done throughout the storage life. The pH, titratable acidity, lipase activity, and protease activity were also measured. The shelf life of pasteurized milk, as determined by aerobic plate count (APC) and acidity indicators, was 24, 36, and 72 hours at 19, 15, and 13°C, respectively. Milk stored at 5, 7, and 10 °C had shelf lives of 30, 24, and 12 days, respectively.
The relationship between bacterial counts and VOC formation in whole (3.9% fat) milk stored under various storage conditions was investigated. In addition, VOC formation was measured using solid-phase microextraction (SPME) with gas chromatography. Microbiological data well correlated with both off-flavors and gas chromatography–mass spectrometry (GC-MS) data. After inception, VOCs increased, with bacterial counts of 5.0 – 7.0 CFU/ mL. Development of a colorimetric VOC detection system for stored milk was the overriding goal of this dissertation. Spoilage bacteria were detected by the nanosensor colorimeter at all storage temperatures. The nanosensor response correlated well with microbial growth counts in the milk samples. Milk spoilage was determined with the sensor to have occurred at 32, 60, and 84 hours at 19 , 15, and 13°C, respectively. Color change, recorded as total color difference (ΔE), correlated well with ABC levels (6.0 -7.0 log10 CFU /mL) in milk (with the exception of the 7°C samples), demonstrating that chemical interactions occur between the nanosensor and the VOCs. These results suggest that the nanosensor has good potential as a real-time VOC sensor for monitoring microbial spoilage in milk during storage and transport. Further development of rapid detection methods for spoilage microorganisms can be based upon the present sensor.
Metrics
11 File views/ downloads
22 Record Views
Details
- Title
- DEVELOPING A SENSOR TO DETECT VOLATILE COMPOUNDS IN MILK TO MONITOR SHELF LIFE
- Creators
- Mohamed Ali Ziyaina
- Contributors
- Barbara Rasco (Advisor)Shyam Sablani (Advisor)Coffey Todd (Committee Member)Gulhan Unlu (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Food Science, School of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 146
- Identifiers
- 99900581717901842
- Language
- English
- Resource Type
- Dissertation