Document Type Master's Dissertation Author Lemmer, Yolandi email@example.com URN etd-11102010-174626 Document Title Effect of enzymes and emulsifiers on the shelf life of modified atmosphere packaged par-baked pizza Degree MSc Department Food Science Supervisor
Advisor Name Title Dr M N Emmambux Co-Supervisor Prof E M Buys Supervisor Keywords
- par-baked pizza
Date 2010-09-02 Availability unrestricted Abstract
Par-baked pizza was prepared with three different additives treatments and was packaged in three packaging treatments namely: air (A), 100% CO2 modified atmosphere (MAP) and 100% CO2 modified atmosphere with an oxygen absorber (MAP + OA). The additive treatments were diacetyl tartaric acid esters of mono- and diglycerides (DATEM), an enzyme combination treatment (EC) namely: lipase and maltogenic á-amylase and par-baked pizza without additives (C). The aim of the study was to determine the effects of the different additive and packaging treatments on the shelf life of par-baked pizza. Therefore the following physical measurements and microbiological analysis were conducted: water activity, crumb moisture content, thickness, firmness, stress, strain, springiness, aerobic plate count, lactic acid bacterial count and yeast and mould count.
The results showed that the water activity of par-baked pizza was between 0.95–0.98 . Thereafter the water activity remained stable at 0.96. As the storage time (d) progressed, the moisture content of the par-baked pizza crumb increased, from 36% on d0 to 41% on d16.
The par-baked pizza with added additives was thicker than par-baked pizza without additives. The thickness for par-baked pizza + DATEM, + EC and + C was 21.7 mm, 22.0 mm and 18.3 mm respectively.
The compression test and the three-point bend test showed that the firmness of parbaked pizza increased as the storage time increased until d8. The firmness then decreased from d12 to d16. The par-baked pizza packaged + MAP had a lower firmness than par-baked pizza + A. The firmness of par-baked pizza + EC was lower than par-baked pizza + DATEM and par-baked pizza + C respectively. The results also showed that the re-baked pizza was even softer than originally.
The springiness of par-baked pizza decreased as the storage time progressed. The par-baked pizza + C had the highest springiness of 39% compared to the springiness of par-baked pizza + EC; 37%, and + DATEM; 35%, respectively. The springiness of the re-baked pizza showed trends similar to those of the par-baked pizza in terms of the main effects of the different additives. The springiness of the re-baked pizza was also higher than that of the par-baked pizza. Thus, the additive treatments, DATEM and EC, had beneficial effects on the texture and thickness of par-baked pizza.
The microbial analysis showed that the APC and the mould count were mostly affected by the different packaging treatments. The par-baked pizza + A showed visible mould growth from d12. Hence par-baked pizza + A reached the end of shelf life at d12. The par-baked pizza + MAP showed reduced APC levels, however, and as expected the yeast and lactic acid bacterial levels were unchanged. There were no signs of visible mould growth on any par-baked pizza + MAP. The microbial levels were the lowest with the par-baked pizza + MAP + OA packaging treatment.
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Please cite as follows:
Lemmer, Y 2009, Effect of enzymes and emulsifiers on the shelf life of modified atmosphere packaged par-baked pizza, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-11102010-174626/ >E10/754/gm
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