DOSSIER: Fresh stuffed pasta - Regeneration of frozen food

Fresh stuffed PASTA

Fresh pasta, stuffed pasta, successful products based on meat or cured meats as indispensable ingredients for traditional or innovative stuffing and dressing. Production line manufacturers and finished product manufacturers are always committed to study new technologies and applications

According to recent Doxa/ Unaitalia research, lasagna tops among Italians’ favourite first courses in celebration or Sunday meals, with Millennials in front; 24% prefer fresh stuffed egg pasta, tortellini, ravioli, etc. 1 Italian out of 2 prefers the traditional recipe. With regard to innovation, 2020 Doxa study reveals that Italians appreciate new products when these concern their emotion without affecting their certainties. Readyto-eat food is judged innovative by 37% of Italian, on the condition that it is good and healthy. 23% of Italian thinks that sustainability and new tastes are important, as a reevaluation of ancient or forgotten raw materials. The manufacturers have a demanding task: they must study new technologies and analyse consumption trends to conquer/keep an important position in the market on the one hand; maintain a stable position, instil trust in the consumer by taking inspiration from tradition on the other. In this context a clear, widespread and comprehensible communication becomes indispensable. Stuffed pasta is successful for several reasons, the main being: • it’s easy and quick to cook • there are many types and sizes • shelf life of 2 to 3 months. Italians are willing to pay a suitable price to taste fresh pasta, especially stuffed pasta: from 3-4 euros per kg to 20 euros per kg, with an average price around 10 euros per kg for mass market retailers.

Regeneration of frozen food

Introduction to the validation of indications contained in the labels of frozen lasagna - case study

Daniela Merigo, Elena Dalzini*, Elena Cosciani-Cunico, Paola Monastero, Alessandro Norton, Stefania Ducoli, Guido Finazzi, Marina-Nadia Losio - Food Control Department, Experimental Zooprophylactic Institute of Lombardy and Emilia Romagna, “Bruno Ubertini”, Brescia, Italy *Correspondent Author: elena.dalzini@izlser.it

INTRODUCTION

Consumers’ demand for ready-to-eat products or frozen foods that can be consumed at home or on the job after regeneration in traditional or microwave oven has increased in the last years. The temperature required to guarantee the appetibility and the safety of foods depend on the food itself, on its composition, conservation, the previous processing it has undergone, and on the package that contains and protects it. It’s manufacturer’s duty to give the final consumer all the indications for proper regeneration, which in case of frozen foods include regeneration method (conventional oven or fanassisted oven, microwave, pan), time (usually minutes or seconds), and the minimum temperatures that must be reached at the end of the treatment (minimum temperature in the core of the product). These indications guarantee the regeneration and the consumption of a microbiologically safe product for the consumer. It’s manufacturer’s responsibility to show that every possible measure has been adopted to pursue this goal. In fact, inadequate regeneration instructions might cause the product to be unsuitably warm, so less pleasing, or worse it may cause food poisoning (ECFF, 2006). Listeria monocyogenes is one of the most hightemperature-resistant pathogenic microorganisms (in vegetative form), and is even able to multiply at cold refrigeration temperatures.

The destruction of this bacterium requires a suitable thermal process, the right combination of time and temperature, to eliminate or reduce the risk. The usually accepted thermal process to make food safe requires that the coldest part of the product is heated to 70°C for 2 minutes (conventional process), which is enough to reduce L. monocytogenes to 6 Log UFC/g (ECFF, 2006). In practice, the same reduction can be achieved by heating the product up to higher temperatures for shorter times or at lower temperatures for longer times, or with dynamic thermal treatments where the temperature changes during the process (Stringer and Metris, 2018). The manufacturer is requested to show that the regeneration indications on the label report a process of 70°C for 2 minutes. Predictive microbiology is particularly helpful in thermal treatment validation: this branch of microbiology supposes that bacteria’s growth, survival or death is conditioned by some environmental variables (temperature, pH, water activity, preservatives, bacterial flora, etc); if we observe how bacteria react to these environmental factors, then we can predict how the microorganisms will react to any condition in the environmental region where observations

Figure 1 – Thermal profiles (blue lines) recorded during the tests in the core of the product kept 35 minutes in fan-assisted oven pre-heated to 180°C. The temperature limit of 70°C used to study equivalent processes is marked in red.

Figure 2 - Equivalent thermal processes (green triangles): the equivalent process at 70°C for 2 minutes has been reached in the product core after 31 minutes in fan-assisted oven at 180°C. The blue line indicates the ‘worst’ thermal profile detected in the core of a product that has been treated in fan-assisted oven at 180°C for 35 minutes. Overall, this process is equivalent to a treatment at 70 °C for 184 minutes.

have been made (Stringer and Metris, 2018). Meat ragout lasagne with béchamel are a typical dish of Italian tradition, they are very popular among the frozen ready-to-eat first courses sold in the supermarkets. This study was aimed at investigating the time-temperature profile recommended by the manufacturer to regenerate frozen lasagna and convert it in minutes equivalent to 70°C, and at studying the product safety for the final consumer.

INVESTIGATION MODALITY

Regeneration directions indicated by frozen lasagna manufacturers have been tested in the Production Support Laboratory of the Experimental Zooprophylactic Institute of Lombardy and Emilia Romagna, simulating consumers’ actions. In the preliminary test, lasagna has been defrosted to insert a Data Logger (a button probe that is able to measure and reveal the temperature of food during the thermal process) in the coldest point of the product. At the end of this step, the product has been frozen to -20°C, which means normal sale conditions. The test has been caried out in a traditional fan-assisted oven pre-heated to 180°C for 35 minutes, and each measurement has been made in 2 different packages of frozen lasagna, in order to consider the variability of the product (heterogeneous food). The whole test has been repeated on three different days. At the end of the trials, the thermal profiles have been elaborated and the ‘worst’ thermal profile has been used to calculated the equivalent processes and the theoretical lethal effect of the thermal treatment by means of spreadsheets available online (NAMI Process Lethality Determination Spreadsheet). The study has used the parameters of thermal resistance of L. monocytogenes available in literature (Van Asselt and Zwietering, 2006).

RESULTS

Projecting, study and validation steps of regeneration indications supplied by the manufacturer, and the calculation of equivalent thermal processes are necessary to guarantee safe frozen ready-to-eat products. In this study, the thermal profiles obtained from simulation trials of domestic regeneration of frozen lasagna have been analysed and reported in Figure 1. All the detected profiles have shown that time and temperature limit of 2 minutes at 70°C in the product core has been reached, and product safety was guaranteed. The ‘worst’ thermal profile was detected during the test carried out on Day 2 in package 2. In this case the product core has reached the 70°C safety limit after 29 minutes of treatment (Figure 1). The profile has been analysed to calculate the equivalent thermal process (Figure 2) and the theoretical lethal effect. Even considering the ‘worst’ profile, the process equivalent to 70°C for 2 minutes is reached in as short as 31 minutes in the product core (Figure 2), with a theoretical lethal effect of L. monocytogenes equal to approximately 6 Log CUF/g. On the whole, the dynamic thermal profile of frozen lasagna regenerated in a fan-assisted oven preheated to 180°C for 35 minutes is equal to a conventional process at 70°C for 184 minutes (Figure 2). This knowledge enables the manufacturer to choose whether prolong or shorten the regeneration times suggested to the consumer, in order to guarantee better products, considering that product safety is guaranteed with over 31 minute long treatments.

CONCLUSIONS

From a microbiological point of view, cooking thermal treatments are today among the most widespread methods to guarantee the destruction or reduction of the main food pathogens in their vegetative state. Manufacturers shall nevertheless define and validate these treatments in order to provide a scientific proof of their effectiveness, to reduce eventual microbiological contaminations and guarantee food safety. In this sense, predictive microbiology can be a useful and quick tool to study and optimize a specific cooking process, in order to establish which times and temperatures are enough to reduce or eliminate a given microbiological risk. 

BIBLIOGRAPHY

- ECFF (2006). European Chilled Food

Federation, Recommendations for the production of pre-packaged chilled foods. Available at: https://www.ecff.net/ wp-content/uploads/2018/10/ECFF_

Recommendations_2nd_ed_18_12_06. pdf. Ultimo accesso:20/01/2022 - Van Asselt, E. D., and Zwietering, M. H. (2006). A systematic approach to determine global thermal inactivation parameters for various food pathogens. International Journal of Food Microbiology, 107(1), 73-82. - Stringer, S. C., & Metris, A. (2018). Predicting bacterial behaviour in sous vide food.

International Journal of Gastronomy and

Food Science, 13, 117-128. - NAMI Process Lethality Determination

Spreadsheet. Available at: http://meatpoultryfoundation.org/content/pro

The authors are responsible for the opinions expressed in the articles and relevant bibliographies