300 ◾ Fundamental Food Microbiology
compounds react with lipases to produce color or fluorescent products have also been developed,
but they have limitations. Recently, a rapid and sensitive sandwich ELISA method was tested to
determine lipases of Pseudomonas spp. An antibody produced against a Pse. fluorescens strain and
linked to horseradish peroxidases reacted with lipases from many strains of Pseudomonas spp. The
reliability and sensitivity of this technique are being studied.
Conclusion
Food spoilage causes not only economic loss but also unavailability of food, especially in places
of food shortage and with high populations, such as in some developing countries. To reduce
both, efficient techniques need to predict storage potential of foods, especially because the consumption of processed foods is going to increase. The methods now used have limitations and
are not highly efficient. New methods that are now being studied could be more effective in the
future. One of these methods is the development of biosensors, which could detect important
bacterial metabolites at very low concentrations. Another method is to determine bacterial load
rapidly by PCR. However, this technique cannot differentiate between live and dead cells. Recent
approaches involve the use of molecular typing methods that allow analysis of the microbial
community to assess the microbial quality of products. As with lactic acid bacteria at present, if,
in the future, the genome sequences of important spoilage bacteria become available, better and
specific biosensors and PCR techniques can be developed to detect spoilage potential of a food
at an early stage.
QUESTIONS
1. List the factors to be considered in selecting indicators of food spoilage.
2. List two spoilage aspects that a suitable food spoilage indicator should indicate to prevent
loss of a food by spoilage. Explain why different indicators need to be selected for different
groups of foods.
3. Suggest and justify suitable microbial spoilage indicators for (a) tray-packed raw sausage;
(b) vacuum-packaged, low-fat, refrigerated ground turkey; (c) fish fillet kept over ice in air;
(d) salsa in a bottle stored at room temperature; (e) ready-to-eat baby carrots, ready-to-eat
salads, and sprouts of seeds packaged aerobically in bags and stored at approximately 15°C;
and (f) cut fruits in aerobically packaged containers at 15°C (consult Chapter 20).
4. List four chemical methods that can be used to detect spoilage of fresh meat stored at refrigerated temperature under aerobic conditions.
5. Explain how pH changes in fresh meats can be used as an indicator of spoilage. How is it
related to WHC and ERV?
6. What promises does genome-based nanotechnology hold for the future to detect microbial
spoilage potential of a food?
References
1. Davies, S., Fighting food poverty, Eng. Technol., 7, 48–49, 2012.
2. Bulushi, I.A., Poole, S., Deeth, H.C., and Dykes, G.A., Biogenic amines in fish: Roles in intoxication,
spoilage, and nitrosamine formation: A review, Crit. Rev. Food Sci. Nutr., 49, 369–377, 2009.
compounds react with lipases to produce color or fluorescent products have also been developed,
but they have limitations. Recently, a rapid and sensitive sandwich ELISA method was tested to
determine lipases of Pseudomonas spp. An antibody produced against a Pse. fluorescens strain and
linked to horseradish peroxidases reacted with lipases from many strains of Pseudomonas spp. The
reliability and sensitivity of this technique are being studied.
Conclusion
Food spoilage causes not only economic loss but also unavailability of food, especially in places
of food shortage and with high populations, such as in some developing countries. To reduce
both, efficient techniques need to predict storage potential of foods, especially because the consumption of processed foods is going to increase. The methods now used have limitations and
are not highly efficient. New methods that are now being studied could be more effective in the
future. One of these methods is the development of biosensors, which could detect important
bacterial metabolites at very low concentrations. Another method is to determine bacterial load
rapidly by PCR. However, this technique cannot differentiate between live and dead cells. Recent
approaches involve the use of molecular typing methods that allow analysis of the microbial
community to assess the microbial quality of products. As with lactic acid bacteria at present, if,
in the future, the genome sequences of important spoilage bacteria become available, better and
specific biosensors and PCR techniques can be developed to detect spoilage potential of a food
at an early stage.
QUESTIONS
1. List the factors to be considered in selecting indicators of food spoilage.
2. List two spoilage aspects that a suitable food spoilage indicator should indicate to prevent
loss of a food by spoilage. Explain why different indicators need to be selected for different
groups of foods.
3. Suggest and justify suitable microbial spoilage indicators for (a) tray-packed raw sausage;
(b) vacuum-packaged, low-fat, refrigerated ground turkey; (c) fish fillet kept over ice in air;
(d) salsa in a bottle stored at room temperature; (e) ready-to-eat baby carrots, ready-to-eat
salads, and sprouts of seeds packaged aerobically in bags and stored at approximately 15°C;
and (f) cut fruits in aerobically packaged containers at 15°C (consult Chapter 20).
4. List four chemical methods that can be used to detect spoilage of fresh meat stored at refrigerated temperature under aerobic conditions.
5. Explain how pH changes in fresh meats can be used as an indicator of spoilage. How is it
related to WHC and ERV?
6. What promises does genome-based nanotechnology hold for the future to detect microbial
spoilage potential of a food?
References
1. Davies, S., Fighting food poverty, Eng. Technol., 7, 48–49, 2012.
2. Bulushi, I.A., Poole, S., Deeth, H.C., and Dykes, G.A., Biogenic amines in fish: Roles in intoxication,
spoilage, and nitrosamine formation: A review, Crit. Rev. Food Sci. Nutr., 49, 369–377, 2009.