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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

MethodsFigure 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 that1. Dries’ formulation performs similarly to competitors2. 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.