Phone: (+39) 0250316659
Fax: (+39) 0250316672
Via Celoria 2, 20133 Milano (Italy)

Shelf Life

Freshness decay and shelf life predictive modeling of European sea bass (Dicentrarchus labrax) applying chemical methods and electronic nose

European sea bass (Dicentrarchus labrax) is one of the finfish species preferred by the consumer, who requires fish freshness to be maintained during distribution and retail. For this reason, the purposes of this study were to define: the shelf life at three storage temperatures (-0.5, 4.8 and 16.5 °C) by applying both chemical (TVB and TBA assays) and olfactometric (e-nose) method; the actual time–temperature exposure conditions during marketing; the prediction of remaining shelf life in the commercial chain, on the basis of time–temperature history data and on appropriate integration routine. Shelf life study revealed the efficacy of chemical markers and electronic nose in describing the freshness decay and in defining a freshness threshold. Freshness of sea bass was kept for about 8 days for fish preserved in melting ice (-0.5 °C), 4 days at 4.8°C and about 1 day at 16.5 °C. When fresh European sea bass was purchased, 9 out of 10 times the remaining shelf life was more than 55% at an average temperature of 1.19 °C. Therefore, the freshness of fish can be assured for 3–4 days in commercialization. A joint effort (sales point management and consumer advertising) could reduce the exposure temperature by 1–2°C and justify an extension of the shelf life to 2–3 days after purchase.

Limbo, S., Sinelli, N., Torri, L., Riva, M. 2009. Freshness decay and shelf life predictive modelling of European sea bass (Dicentrarchus labrax) applying chemical methods and electronic nose. Food Sci. and Tech. (LWT). 42: 977–984

Prediction of Remaining Shelf Life of fresh sea bass during the whole commercialization chain: (:) TVB stability times, (r) TBA stability times, (C) electronic nose stability time. 0. Delivery to retailer; 1. Storage at the retailer; 2. Rest in the truck (before transport); 3. Delivery; 4. Storage at the sale points; 5. Rest on the exposure bench; 6. Transport to home; 7. Home storage.

Predictive modelling of the freshness of minced beef meat stored in MAP at different temperatures.

The aims of this work were: 1) to follow the freshness decay of packaged minced beef meat stored at different temperatures (4.3, 8.1 and 15.5°C) by applying both traditional methods (microbiological counts, TBA assay, headspace gas composition) and non-invasive methods (e-nose and color measurement); 2) to model the kinetics in order to obtain information about the maximum acceptability time as function of storage conditions. The minced beef, packaged with high gas barrier materials in modified atmosphere was directly supplied by a manufacturer at the beginning of its commercial life and analyzed at different times according to the storage temperature. Shelf life study revealed the ability of the traditional methods in describing the kinetic of freshness decay. The classical modeling of the experimental data and the comparison with microbiological or chemical thresholds allowed the setting, for each index, of a stability time above which the meat was no longer acceptable. The quality decay of meat was also evaluated by inspecting the headspace fingerprint of the same set of samples by means of a commercial e-nose. A clear discrimination between “fresh”, “old” and “very old” samples was obtained by using PCA and CA, determining at each temperature a specific range of stability time. Colour attributes were evaluated by using conventional colorimeter. All the stability times estimated for each index allowed the building of a generalized time-temperature tolerance chart, obtaining also a Q10 mean value. The results show that the Q10 values from the traditional methods (3.6-3.8 range) were accordingly overlapped with the Q10 estimated with e-nose and colour indexes (3.4 and 3.3 respectively).

Limbo, S., Torri, L., Sinelli, N., Franzetti, L., Casiraghi, E. 2009. Predictive modeling of the freshness of minced beef meat stored in MAP at different temperatures. Submitted to Meat Science.

Shelf-life modeling of moisture sensitive food products.

The water vapour sorption isotherms of different types of dried “starch-based” products were determined at 25°C and the experimental data were fitted through available sorption equations. The goodness of fit was evaluated by means of the mean relative deviation modulus and the equation with the best fit was selected. The sorption isotherm equation, the permeability values of the packages and others product characteristics were used together in a mathematical model to predict the moisture gain by packaged biscuits and crackers. Good agreement was found between the experimental data obtained from actual storage testing of the same products and those predicted by the model.
A mathematical model able to predict the storage life of cereal-based dry foods was also developed in order to assess the influence on the shelf life of cereal-based dry products of both the water barrier properties of the package and the affinity of the packed food with water. Three different cereal-based dry foods and 3 different polyamide films were investigated. It was found that the shelf life of the investigated food s, as predicted by means of the proposed model, could be overestimated by about 90% if the dependence of water permeability coefficient on water activity inside and outside the package is neglected.

Fava.P., Limbo, S., Piergiovanni, L. 2001. Shelf-life modeling of moisture sensitive food products. Industrie Alimentari 39: 121-128
Del Nobile, M.A., Buonocore, G.G., Limbo, S., Fava, P. 2003. Shelf life Prediction of Cereal-based Dry Foods Packed in Moisture-sensitive Films. Journal of Food Science. 68 (4): 1292-1300.

Innovative approaches and instruments in modeling and monitoring the shelf life of packaged perishable foods.

The development of improved methods to determine food quality such as freshness, microbial spoilage, oxidative rancidity or oxygen and/or heat induced deterioration is extremely important to food manufacturers. In order to maximize the quality and safety of foodstuffs, a prediction of shelf-life based on standard quality control procedures is normally undertaken. Replacement of such time-consuming and expensive quality measurements with rapid, reliable and inexpensive alternatives has lead to greater efforts being made to identify and measure chemical or physical indicators of food quality. The possibility of developing a sensor for rapid quantification of such an indicator is known as the marker approach. In this research chemical or physical indexes of food quality will be identified for defined products, in order to measure them with sensors. It will be applied a direct approach in case of a primary measurable variable related to shelf life or a marker approach in case of an indirect indicator of shelf life. On the basis of the collected data, existing shelf life prediction models will be incorporated and verified with mathematical software packages that can reproduce and predict the shelf life of the products. New models will also be developed. The use of mathematical models to predict the shelf life and characteristics of different product formulations should always be used with caution and, for this reason, the predicted shelf life will be compared with the real one in order to verify the reliability of the models and to allow corrections.

Lamiani.P., Limbo, S., Piergiovanni, L. Innovative approaches and instruments in modeling and monitoring the shelf life of packaged perishable foods. PhD thesis, ongoing.

Shelf life of minimally processed potatoes. Effects of high oxygen partial pressures in combination with ascorbic and citric acids on enzymatic browning and loss of some quality traits.

The aim of this work was to study the effects of high oxygen partial pressures in combination with ascorbic and citric acid on the development of the enzymatic browning and on loss of some quality traits of peeled and cut potatoes (‘Primura’ variety). Sliced potatoes were stored in flexible packaging under different oxygen partial pressures (10, 55 and 100 kPa) after dipping treatments with ascorbic and citric acid at different concentrations according to a central composite design. The browning development during storage was measured by a tristimulus colorimeter. Second-order polynomial models were computed for three periods of storage (3, 7 and 10 days) to relate the independent variables (oxygen partial pressure, ascorbic and citric acid concentrations) to the colour function attributes. When potatoes were stored in the presence of high oxygen partial pressures, the ascorbic acid concentration was a critical variable and its concentration should be correctly modulated. In fact, during storage the enzymatic browning was reduced if this agent was not used or it was used at very high concentrations. On the contrary, the use of citric acid alone seemed to be enough for a significant inhibitory effect on PPO when very high oxygen partial pressures were used. The respiration rate did not increase in direct linear proportion to the oxygen partial pressure and there was no significant difference in respiration between 55 and 100 kPa, even though the respiration rate was higher at these super-atmospheric oxygen levels than at 10 kPa. Citric acid did not affect the respiration significantly, while the respiration rate increased with the increase in ascorbic acid concentration. However, at the highest level of ascorbic acid tested (5%), the respiration rate decreased. Finally, High oxygen partial pressures (55 and 100 kPa) did not stop the production of hexanal but they had an inhibitory effect on the anaerobic volatiles production.

Response plot of the CO2 accumulation rate inside flexible pouches as function of O2 and ascorbic acid.

Limbo, S., Piergiovanni, L., Limbo, S. 2007. Minimally processed potatoes. Part 2: Effects of high oxygen partial pressures in combination with ascorbic and citric acid on loss of some quality traits. Post. Biol. Techn. 43: 221-229
Limbo, S., Piergiovanni, L. 2006. Minimally processed potatoes. Part 1. Effects of high oxygen partial pressures in combination with ascorbic and citric acid on the enzymatic browning and quality decay of minimally processed potatoes. Postharv. Biology and Techn. 39: 254-264

Influence of Packaging Material on Bread Characteristics during Ageing.

One of the priorities of today’s bread-making industry is to find suitable packaging solutions to satisfy the peculiar requirements of bread, mostly appreciated by Italian consumers for its crispy crust. The packaging material should allow for both rapid heat exchange with the environment and water vapour evaporation to prevent condensation inside the package. Perforated orientated polypropylene (OPP) films are currently the best materials available for satisfying the industry’s
requirements. Recently, our group demonstrated that bread wrapping with perforated films is efficacious against bread contamination. The aim of this work was to verify whether these types of films could also influence the trend of phenomena related to product ageing. In particular, variations in the moisture inside the loaf during storage and their influence on changes in crumb softness were investigated. Three OPP films and one double-layer film bag with different hole
size characteristics were chosen for this study and their performances were compared with those of a paper bag. Because of the considerable differences in the hole size characteristics, the films showed very different barrier effects to water evaporation. The C250 OPP film (hole mean diameter = 0.54mm and density = 21.4 holes/cm2) played an interesting role in modulating moisture variations. Wrapping bread in this film enabled both crust crispness and crumb softness to be maintained during 48h of storage. Such performances cannot effectively be obtained
by using alternative industrial bread packaging materials, such as paper bags.

Pagani, M.A., Lucisano, M., Mariotti, M., Limbo, S. 2005. Influence of packaging material on bread characteristics. Pack Techn and Sci. 19: 295-302
Piergiovanni, L., Limbo,S., Riva, M., Fava, P. 2003. Assessment of the risk of physical contamination of bread packaged in perforated oriented polypropylene films: measurements, procedures and results. Food Addit. and Contam. 20 (2): 186-195

Bread moisture distribution at different storage times in the three bread areas (A: the slice core; B: the crumb; C: the slide edge; e: external slices; i: internal slices

Accelerated shelf life testing: possible applications of a new instrument (Oxitest) to oxygen sensitive food products.

Chemical reactions occurring between atmospheric oxygen and food sensitive components are some of the most important causes of food product degradation, thus the possibility to foresee their effects in time is always of great interest in shelf life studies.
The aim of the project is to evaluate the applicability, in auto-oxidation reaction studies, of a new instrument in accelerated shelf life studies of oxygen sensitive food products.
Differently from similar and already validated methods, such as Rancimat (Metrohm) and Oxygen Stability Index (OSI Omion Inc.), the easiness to use, due to the possibility to perform the analysis directly on the food (liquid, solid or pasty) without previous fat separation, represents the most important Oxitest benefit. The information obtainable from instrument response regards not only the Induction Period (IP) of the autoxidation process, but also the rate and acceleration of the autoxidation itself. The amount of oxygen consumed by the food product during oxidation can be obtained as well. This instrument is based on the absolute pressure change in a closed and thermostatted room, monitoring the oxygen up-take by different food products.
The aim of this work was to propose a standard operating procedure in order to verify the reliability of the measuring system under normal laboratory conditions and to investigate one of the possible applications of OXITEST. For this reason the following steps were considered:

  • The evaluation of some parameters of validation in accordance with the Eurachem Guidelines;
  • to test the ability of OXITEST in revealing adulteration of vegetable oils;
  • the applicability of OXITEST to the monitoring of the oxygen up-take by different food products.

The results show that the detection and quantification limits found for the Oxitest, the high degree of correlation with OSI method and the easiness to use, make Oxitest competitive towards similar techniques. Oxitest, already used for the control of suppliers and food raw materials QC, can be used satisfactorily on finished foods as well. The ability of Oxitest in revealing adulterated oils has been pointed out and confirmed as one of the important possible applications, being the authenticity of products labelled as extra-virgin olive oil of paramount importance from the standpoints of both commercial value and health aspects. The new instrument demonstrated to be a useful device for evaluating lipid stability, under accelerated conditions, of fats, oil and whole products. It also made possible, indirectly, to measure the efficacy of preservation conditions and to evaluate the product shelf life because it was able to discriminate among different aged products.

Indino, L., Piergiovanni, L., Maiocchi, P.2004. Accelerated shelf life testing: possible applications of a new instrument (Oxitest) to oxygen sensitive food products. Special Issue of Italian Journal of Food Science. L.Piergiovanni and S.Limbo (Eds). Chiriotti Editori, Italia

Mora, L., Limbo, S., Maiocchi, P., Caboni, M. F., Verardo V., Comandini, P.2008. Preliminary validation of a new instrument for studying food oxidative stability. In Shelf life degli alimenti confezionati. (Shelf life of packaged foods). Special Issue of Italian Journal of Food Science. Chiriotti Editori, Pinerolo, Italia. In press