OPTIMIZATION OF AN ALGINATE BASED EDIBLE COATING WITH BEESWAX, NISIN AND EDTA TO MAXIMIZE SHELF LIFE OF FRESH MUSHROOMS (Agaricus bisporus)

Open Access
Author:
Luttmann, Anneliese
Graduate Program:
Food Science
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
September 08, 2011
Committee Members:
  • Ramaswamy C Anantheswaran, Thesis Advisor
  • John D Floros, Thesis Advisor
Keywords:
  • nisin
  • beeswax
  • alginate
  • edible coating
  • optimization
  • Mushrooms
  • EDTA
  • minimal processing
Abstract:
Fresh white button mushroom (Agaricus Bisporus) is a highly perishable crop with limited shelf life. Enzymatic browning, bacterial spoilage and high respiration rate are the main causes of quality deterioration. Calcium alginate coatings with lipids, antimicrobial, and chelating agents can delay quality deterioration and extend shelf life. The three objectives of this thesis were to evaluate the effect of three coatings: alginate (A), alginate containing beeswax (AB), and alginate containing beeswax, nisin and Na2EDTA (ABN) on the quality of fresh white button mushrooms; to determine the effect of alginate, beeswax, nisin and Na2EDTA concentration on the quality of fresh white button mushroom as measured by color change (&#916;L*), weight loss (WL), degree of cap opening (MI) and bacterial growth (BG); and to optimize the coating composition that maximizes shelf life using response surface methodology. As part of the first objective of this thesis, mushrooms were coated with A, AB and ABN and stored at 12°C/60%R.H. for 16 days. After 8 days of storage, mushrooms coated with ABN had significantly (p<0.05) lower &#916;L* as compared to uncoated control (C). Coatings AB and A had significantly (p<0.05) lower &#916;L* as compared to C after day 14 and 16 respectively. No significant difference (p>0.05) was found in the rate of WL compared to C. Mushrooms coated with A, AB and ABN had significantly (p<0.05) lower MI as compared to C. Mushrooms coated with ABN had significantly (p<0.05) lower BG during the early days of storage. Overall, shelf life of mushrooms coated with ABN was extended by 6 days. These results indicate that edible coatings can be used to extend shelf life of fresh mushrooms. As part of the second objective of this thesis, mushrooms were coated with various concentrations of alginate, beeswax, nisin and Na2EDTA as determined by a central composite experimental design, and stored at 12°C/60%RH for 16 days. Alginate significantly (p<0.01) reduced the rate of BG throughout storage. Beeswax significantly decreased &#916;L* (p<0.01) and BG (p<0.05) after 6 days in storage, but increased WL (p<0.10). Na2EDTA significantly reduced &#916;L* (p<0.05) and BG (p<0.01), while nisin significantly decreased &#916;L*(p<0.10) and MI (p<0.01) during days 0-6. Nisin also increased WL significantly (p<0.05) throughout storage, but significant (p<0.01) interactions indicated that at high concentrations of Na2EDTA and alginate, this effect was reduced. As part of the third objective of this thesis, response surface methodology (RSM) was used to find the optimal concentration of each compound to maximize shelf life by reducing &#916;L*, MI and BG. The optimal coating contained 2.49% alginate, 0.82% beeswax, 8.18mg/mL Na2EDTA and 4000IU/mL nisin. In a validation study, &#916;L* and MI measurements of mushrooms with the optimal coating were compared to those of the uncoated control. The optimal coating significantly (p<0.05) reduced &#916;L* and MI, extending the shelf life 7 days past that of the control.