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Most undergraduate students undertake a research project as an integral part of a degree with 'honours' in Britain and Ireland. Some of these projects are undertaken to a high standard and are worthy of wider dissemination. Due to time and cost constraints the replication required for formal publication is often not possible.
I have decided to provide a forum for the wider dissemination of good quality student projects on the Dairy Science and Food Technology website. Contributions are welcome and should be sent to webmaster at dairyscience.info.
Every year I get requests from students for research topics for final year projects. The following is a short list of potential food science, food technology, food microbiology projects that reflect current issues in 2016.
The growth of thermophilic streptococci in pasteurisers during long production runs has been known for some time (Driessen and Bouman, 1979). These organisms include Streptococcus thermophilus and organisms that are referred to as Str. thermophilus-like (Mullan, 2003); they have some of the phenotypic characteristics of Str. thermophilus but differ in that they grow in 4% salt solutions and utilise maltose and other carbohydrates. The Str. thermophilus-like bacteria were designated as Str waius by Flint et al. (1999) but were later reclassified as Str. macedonicus (Manachini et al., 2002).
Growth of Str. thermophilus and Str. thermophilus-like lactic acid bacteria to high concentration in milk in pasteurizers can cause significant problems in cheese making. These include excessive openness and overt gas production in cheese, off flavours, discoloration particularly in annatto-coloured cheeses and major disruption in process parameters in varieties in which the manufacture is tightly specified e.g. Mozzarella.
In this student project the authors investigated why less starter culture was required throughout the production run in one cheese making plant in Great Britain compared with a similar plant in Ireland.
The project had two major objectives. To:
- determine the concentration of thermoduric LAB in raw milk and milk ex-pasteuriser at the two cheese plants
- identify the thermoduric LAB to species level.
Milk from two cheese production runs was sampled in Ireland. One production run was sampled in Great Britain (due to cost and time constraints). Pasteurised milk samples were taken aseptically, using a syringe, from a sample port post-pasteurisation. Raw milk samples were taken from the pasteurizer-balance tank at both plants. The samples were put into aseptic containers and held at 1-5°C prior to analysis normally within 24 hours of sampling.
Colonies were isolated, purified and allocated to genus as described by Billie et al. (1992) and Aprea et al. (2005) with the exception that the M17 agar used was acidified with hydrochloric acid to give a pH of 5.5 to make it slightly more selective for lactic acid bacteria and to inhibit swarming. API 50 CHL test kits and the API database from Biomerieux, Grafton Way, Basingstoke, Hampshire, England, RG22 6HY were used to confirm genus and allocate isolates to species.
The growth of thermophilic bacteria in pasteurized milk from the cheese plants in Great Britain and Ireland.
No growth was recorded in milk samples plated on Rogosa agar at either plant but growth was recorded on M17 agar.