Scientists working in the Department of Food Science at the University of Foggia claim that the shelf life of amaranth-based homemade fresh pasta could be extended by up to 25 days with use of the polysaccharide chitosan. The team also expects its findings to be applicable at an industrial level.
The shelf life of fresh pasta is affected by microorganisms such as bacteria, yeast and moulds which can grow in the product.
Although research has been carried out into methods of reducing this, such as modified atmosphere packaging, the Italian scientists believe theirs is the first study to examine closely the microbiological stability of fresh pasta based on the traditional grain amaranth.
The scientists examined the antimicrobial activity of the natural compounds thymol, lemon extract, chitosan and grapefruit seed extract (GFSE) on mesophilic and psychotropic bacteria, total coliforms, Staphyloccocus spp., yeasts and moulds. They reported that “chitosan is the most successful among the investigated compounds in slowing down the growth of the above spoilage microorganisms, whereas lemon extract is the least effective”.
Study details
The scientists used amaranth flour and tap water to prepare their own pasta dough. They separately added each of the natural compounds to obtain concentrations of 2000mg/kg of pasta for each of the compounds.
Several controls were also set up: Pasta with no antimicrobials; pasta with 0.3 per cent lactic acid solution; and pasta with 0.16 per cent ethanol.
Each pasta sample weighed 30g and was packed in a high-barrier plastic film and stored at 4ºC, with microbiological analyses performed on each sample over a period of 25 days to determine the activity of the microorganisms.
Results showed that for the entire period of the study, the presence of yeasts and moulds were below experimental detection limits, so these were not taken into account when compiling the results.
The study showed that chitosan was the most effective compound at slowing down the growth of all the microorganisms, with lemon extract having little to no effect in each case. The scientists claim this is consistent with previous studies which have suggested that chitosan can improve food quality and prolong shelf life.
GFSE also had an effect on the growth of all the microorganisms, although this was not as pronounced as that of chitosan. Thymol was effective to a degree in all cases but total coliforms.
Taste test
Tests were also carried out to investigate the influence of the active compounds on the sensorial qualities of the pasta, with a panel of eight trained testers investigating colour, aroma and overall acceptability. They concluded that there was little to no difference between the various pasta samples, “suggesting that the investigated active agents could be advantageously used to control the microbial quality without affecting the sensorial properties”.
Commenting on the results of the study, the scientists said: “It is possible to assess that the technique could advantageously used to prolong the shelf life of amaranth-based homemade fresh pasta. Results also highlight that the above approach could be scaled up to a factory level and combined with other packaging techniques, such as modified atmosphere packaging, to reach higher shelf life.”
Source: Food Microbiology
DOI: 10.1016/j.fm.2008.10.003
Published online ahead of print
“Use of Natural Compounds to Improve the Microbial Stability of Amaranth based Home-Made Fresh Pasta”
Authors: M.A. Del Nobile, N. Di Benedetto, N. Suriano, A. Conte, C. La macchia, M.R. Corbo, M. Sinigaglia