This project aimed to determine the cause of bursting bottles in a local cider manufacturer's extended shelf life product. Tests found that initial microbial contamination was similar to competitors and preservatives were effective. Experiments varying bottle headspace showed less headspace led to faster pressure increase. Therefore, the manufacturer was recommended to reduce the amount filled in each bottle to increase headspace and reduce bursting.

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Improving Apple Cider
Keerthana Krishnarajah, Katherine Mayer, and Joel Toro
Dries Orchards, Inc.
Department of Chemical Engineering, Bucknell University, Lewisburg, PA
Abstract
References
Through the bacterial plating test, we determined that our client had similar or fewer initial colonies than their
competitors. From this, we believe that contamination is not the cause of the bursting problem.
Our experiments to test the effectiveness of the preservatives used by our client showed no change under accelerated
conditions. The pressure gauges on all of the cider samples showed no pressure evolution over a period of two weeks.
Additionally, the turbidity testing displayed no change for each sample over the same timeframe.
Acknowledgements
Dries Orchards is a local cider manufacturer that
provides the private label apple cider brand for Weis
markets. They are currently providing Weis with half
gallon extended shelf life cider. They would like to
expand their sales to include full gallons.
However, a problem with their extended shelf life cider
has arisen where some bottles burst during transit. To
address this issue, we looked at two main areas of
concern:
1. Formulation of the cider
2. Headspace in the bottle
The formulation of the cider is relevant to this problem in
two ways, initial contamination and preservative
effectiveness. Both of these factors contribute to the
formation of gas inside the bottle, which leads to
pressure buildup and subsequent bursting.
We believe that headspace is also a possible cause of
the issue, as if there is not enough space within the
bottle for gas to expand, the bottle will burst.
This project focus on finding possible causes for the variance in shelf life of a local apple cider manufacturer’s product. To do this, the performance of this manufacturer's cider was compared to that of their competitors through an accelerated aging
experiment and microbial plating
Formulation Discussion
Conclusion
Introduction Results
We would like to thank Dries’ Orchards for the opportunity to work with
them. We would also like to extend our thanks to Dr. Prince,
Dr. Vigeant, and all others who lent us their support.
Cider
Average Number
of Colonies (CFU)
Date of First Formation
Competitor 1 1362 4/15/2016
Competitor 2
772 4/15/2016
Competitor 3
378 4/13/2016
Client 425 4/15/2016
Figure 2. Setup to determine the effect
of varying headspace on the time
required to reach certain pressures
Figure 1. Warm bath set up to
measure pressure evolution over time
in competitors’ and client’s cider
Figure 3. A comparison of the amount of time required to reach several pressures with various
amounts of available headspace in a rigid 150 mL bottle
Volume
(mL)
Headspace
(%)
Average Time
to 3 psi (sec)
Factor Time
Changed By
Factor
Headspace
Changed By
160 100 10.7 - -
110 68.8 8.7 1.2 1.5
60 37.6 3.0 3.5 2.7
Methods
Figure 4 (left) Petri dish showing bacteria growth after one day
Figure 5 (right) Petri dish showing bacteria growth after several days
Table 1. An example of how different headspace in a bottle affects the response time for pressure
Table 2. Average number of initial colonies found in tested ciders
Headspace Discussion
The headspace experiments support our initial
hypothesis that as the bottle’s headspace is reduced by
adding more water, the time it takes to reach a certain
pressure is faster. Based on the results from the
formulation experiments, we believe that headspace is
the real problem behind Dries’ bottles bursting.
Using the results of the headspace experiments, we can
recommend a mass of cider that Dries should fill their
bottles with in order to increase headspace. This is
beneficial in two ways:
1. The pressure that builds in the bottle over time will be
reduced
2. Dries will be giving away less free product
From our gathered data we can conclude that
1. Dries’ formulation performs similarly to competitors
2. Headspace does have an effect on the rate of
pressure build up
Based on these results, we recommend that Dries fill
each bottle with less product. We feel this will reduce
the bursting issue, as well as increase profitability.
We also recommend Dries apply this concept to their full
gallon product, in order to be able to sell at Weis.