GCRIS

Now showing 1 - 2 of 2

Bioactive Compound Retention and Shelf Life Extension of Strawberry Juice by Selected Nonthermal Processing Technologies
(Izmir Institute of Technology, 2017) Yıldız, Semanur; Ünlütürk, Sevcan; Barbosa-Canovas, Gustavo V.
Shelf life extension of fruit juices while maintaining quality and functional properties is of great interest. Nonthermal food processing technologies have been emerged as innovative preservation methods alternative to thermal pasteurization of fruit juices. The objectives of this Ph.D. thesis were to (i) ensure microbial safety of strawberry juice (SJ) by thermal and nonthermal technologies, i.e. high pressure processing (HPP), ultrasound (US), pulsed electric field (PEF) and UV-C irradiation; (ii) evaluate physicochemical and phytochemical properties of SJ after processing and during storage; (iii) extend microbial shelf life of SJ without unduly affecting quality. HPP (300 MPa, 1 min), US (120 m, 5.15 J/mL, 55 C, 3 min), PEF (35 kV/cm, 27 s, 155 Hz), and thermal pasteurization (71.7 C, 15 s) conditions were determined based on equivalent inactivation of E.coli (ATCC 11775) in SJ studied at Washington State University. UV-C irradiation (1.01 J/mL, 53.9 C, 6 cycles, 5.8 min) and thermal pasteurization (72 C, 101 s) conditions were determined considering inactivation of E. coli K-12 (ATCC 25253) in SJ studied at IZTECH. Consequently, microbial shelf life of SJ treated by HPP, thermosonication, UVC+mild heating, thermal pasteurization was extended up to 42 days while PEF prolonged up to 35 days at refrigerated storage. Multivariate data analysis revealed that HPP and PEF enhanced phytochemical characteristics of SJ compared to thermosonication and thermal pasteurization. Although UV-C irradiation did not alter physcicochemical properties, total phenolic content, and antioxidant activities of SJ, total anthocyanin content was significantly decreased by UV-C light compared to untreated juice.
Investigation of the Effect of Different Processing Techniques on the Overall Quality and Shelf Life of Local Apricot Variety of Iğdır (prunus Armeniaca L., Cv. Şalak)
(Izmir Institute of Technology, 2017) Hakgüder Taze, Bengi; Ünlütürk, Sevcan
cv. Şalak apricot is a specific type of product with its unique size, shape and taste. However, its distribution and marketing is very limited due to its perishable nature and restricted shelf life. Since drying is not applicable for cv. Şalak apricot due to its low dry matter content, a novel method which would not alter the fruit quality and maintain the product safety was urged to be developed. The objective of this thesis was to explore the effect of combined processing (mild heat (MH) treatment+UV-C irradiation+CaCl2 dipping=MUC) and MAP on the shelf life of cv. Şalak apricots during cold storage. Characteristics of the samples and the effect of MUC on physicochemical properties, enzymatic activities and sensory were determined. At last, samples packed either with MAP or without MAP were stored at 1°C. Microbial quality and physicochemical properties were assessed throughout the storage. Optimum treatment conditions were 19 min at 3.23 mW/cm2 for UV-C irradiation; 6% of CaCl2 at 40°C for 21 min for MH + CaCl2 dipping. MUC treatment did not alter the physicochemical and sensorial properties, PPO and PME activities. After MUC, coliforms were completely inactivated whereas Total Aerobic Plate Count (TAPC) and Yeast and Mould Count (YMC) were reduced by 2.1-log and 2.67-log, respectively. Microbial shelf life of apricots could be extended from 3-5 days up to 14 days by MUC+MAP. Firmness was also maintained. But, MUC adversely affected the colour. On the other hand, MAP application alone was not sufficient to provide the microbial quality.

Phd Degree / Doktora

Browse

Filters

Settings

Sort By

Results per page

Search Results