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How many times have we reached into our fridge for a product to find out it had already hit its labelled expiration date, asking ourselves… will it still be good? There, A Good Opportunity has thought the time has come to shed some light on the subject, asking the Department of Agricultural, Forest and Food Sciences of the University of Turin series of laboratory analysis, ' just to clarify what happens to food when they reach their use-by date or their best before.. date, according to manufacturers.
We chose foods to be tested among the most problematic in terms of conservation (for five out of six expiration dates are fixed by the public authority we have already mentioned) and we had them submitted to the judgment of professional tasters. More couldn’t be done...
Final Report Project "A good opportunity"
Edited by:
Vincenzo GERBI – Giuseppe ZEPPA – Valentina ALESSANDRIA – Giuseppe MUNFULETTO
Introduction
Food industry, which is the first manufacturing industry in Europe and the second nationwide, _ is also one of the productive sectors producing more waste.
A recent study by the FAO (2011) showed in fact that food waste in the world amount to around 1.3 billion tons per year, equivalent to about one-third of the global production of food for human consumption. These data confirm what has been previously pointed out through a study (Smil, 2004) that is only 43% of the products globally cultivated for food are actually consumed. The causes of these losses vary depending on the area in question: in a developing country these losses are in fact concentrated in the first part of the food chain, while in an industrialized country most of the waste occurs in the final stages.
There is no single definition for food waste not institutionally nor within the scientific literature. To ‘straighten out matters ' was the FAO giving a first definition of "Food Waste" and including in this category "any edible and healthy foodstuffs that, instead of being destined for human consumption, is wasted, lost, spoiled or consumed by parasites in each and every stage of the food chain "(FAO, 1981). In a recent study, conducted by the Swedish Institute for Food and Technology in 2011, a distinction has been proposed between:
- "Food losses": food losses that occur during the stages of agricultural production, post-harvest and food processing; depend mainly on farming techniques, infrastructure, environmental and climatic factors, production surpluses and on the respect of production standards and regulations.
- "Food waste": are those taking place along the food chain of industrial processing, distribution and final consumption, whose causes are many, from the technical and structural limitations of both transformation and distribution stages up to the legal aspects, surpluses from immoderate purchases by consumers and mistakes in food preservation. It is necessary to clarify that talking about "Food waste" are taken into account only food that was originally meant to human consumption but which fortuity gets out the human food chain or if it is then directed to a non-food use.
In a study by the Barilla Centre for Food & Nutrition conducted in 2012 were analysed all stages of the agricultural and food chain in order to ascribe the different responsibilities in the production of "Food losses" and "Food waste". This allowed the identification of six main phases:
- Cultivation, agricultural production and crop: losses are mainly due to climatic conditions, farming techniques used and the manufacturing standards.
- First processing and industrial processing: where organic waste might result from limitations in the techniques and technologies used in food processing.
- Distribution: most of the waste is due to products which remain unsold for various reasons (marketing, regulations and quality and aesthetic standards)
- Catering and household consumption: due to overstocked pantries whose food reach its use-by date without being consumed.
Looking at the Italian situation, until recently, the problem of waste along the food chain was not fully taken into account. The first data on this topic date back to 2011, when it was estimated a waste of about 20 million tons of food within the retail chain, and on the basis of data collected by ISTAT in 2009 it was possible to quantify the percentage leftover crops from farmers’ fields, which amounted to 3.25% of the total production.
In the food industry instead of the medium waste amounts to 2.6% of the total (around 1.9 million tons of food) distributed among the various types of food processing. The highest incidence is within the fruit and vegetables processing and preserving, followed by dairy and ice cream industry. The products discarded during these stages might have been affected by some mistakes during processing, being therefore no longer up to the production standards. They are usually thrown away or used as animal feed (Segré and Falasconi, 2011).
In 2009 in Italy, approximately 260,000 tons of finished food products have been wasted in this way, about 40% consisted of fruit and vegetables.
The large volumes of waste produced along the food chain lead to different types of problems:
- Economic: waste disposal appears to be an additional cost for the companies that produce them.
- Environmental: due to emissions of greenhouse gases during the decomposition of these wastes.
- Ethical and Social: large volumes of food waste could be given to the poor who cannot eat regularly reused giving to the poorest people who do not have the opportunity to eat regularly (undernourishment, world hunger). It must be pointed out that one third of the food produced globally is “lost”, while about 860 million people suffer from hunger (www.fao.org).
As previously noted one of the phases contributing to the production of waste is the distribution and particularly the final one, where defective, therefore unsaleable, products as well as products close to expiry are intended for destruction.
The average consumer in fact avoids buying products close to the expiration date, considering them unfit for consumption and this way decreeing their withdrawal from the market and their destruction, with obvious economic and social losses.
The purpose of this project was therefore to verify and demonstrate whether and how a food product, although close to its expiration, may maintain its compositional, microbiological and sensory characteristics, and so can be purchased and consumed just like another one that with a longer shelf-life.
The survey was carried out on six extensively consumed products with an expiration date varying from a few days to a few months (UHT milk, pastry, strawberry yogurt, pasteurized milk, fresh filled pasta, diced cooked ham). All products were purchased at a major supermarket in the Turin area and for each type were selected several packages from the same lot, all of them with the longest shelf life among those available.
In some cases (UHT milk, pasteurized milk, diced cooked ham, and stuffed pasta) were examined products from two different firms, both present in the supermarket.
After being transferred to the DISAFA (Department of Agricultural Sciences, Forestry and Food Agricultural Microbiology and Food Technology) laboratories (keeping whenever possible an unbroken cold chain), the samples were preserved respecting all pre-defined storage conditions for each of them.
In particular, UHT milk was stored in refrigerator at 20 ° C while all the remaining products were placed in a refrigerated chamber at + 5 ° C. The analytical tests were carried out to obtain accurate information about composition, microbiological and sensorial changes during the controlled storage, and to take note of the significant differences in the product at the end of its shelf-life compared to a fresh one.
To this end, the valuations have been carried out on the fresh product just purchased, during storage at regular intervals more or less extensive depending on the shelf life as stated by the manufacturer and on the day of its expiry, or in the next one. Several tests were conducted at regular intervals throughout the sample entire shelf-life established by the producer, and at the time of its expiry or immediately afterwards.
With regard to the physical-chemical indication were evaluated the colour parameters CIELAB, the pH, the structure, the activity water (aw) and the volatile components through electronic nose. As for the microbiological parameters, attention has been paid to the global bacterial count, in yeasts, coliform and lactobacillus.
The chemical and physical and microbiological parameters used for each food were obviously chosen according to the type of food considered, according to the following table:
The colour analysis was performed through a Minolta Spectrocolorimeter CM-5, operating on 1 cm of the optical path length cuvette in the case of liquids, or by means of an integrating sphere for measuring the colour of solid samples.
The pH analysis was performed using a Crison GLP21 50-15 pH meter with pH 50-15 electrode directly on the product in the case of liquids or, in the case of solids, dispersing 10 g of sample in 100 mL of distilled water then measuring the pH value on the obtained suspension.
The aw determination was performed with an Aqualab tool, while for the structure we used a TAXT2 Texture Analyser with probe HDP / TPB (Figure 1).
Figure 1-Texture Analyzer sensor HDP/TPB in the structural analysis of puff pastry
The evaluation of the volatile component was carried out with a Pen3 AIRSENSE working directly on the packaging for the solid products (Figure 2) or by placing the sample in 50 mL vials in the case of liquid (Figure 3).
Figure 2 - Evaluation of volatile component in fresh pasta by electronic nose
Figure 3 - Evaluation of volatile component in milk by electronic nose
In Figure 4 are shown by way of example the profiles provided by the 10 sensors for a sample of milk.
In order to define the differences between the samples was taken into account the same period between 50 and 55 seconds of acquisition, averaging the values for each sensor.
Figure 4 - Example of signal profiles acquired by the electronic nose
All assessments were carried out three times.
As for the microbiological analyses were followed various analytical protocols according to the type of microorganisms to be highlighted. In particular, for the total aerobic count was used the PCA soil (Plate Count Agar, Oxoid) and the plates were incubated at 30 ° C for 48h. Coliforms were searched for on the VRBL soil (Violet Red Bile Lactose Agar, Oxoid) and the plates incubated at 37 ° C for 24h, while the lactobacillus were searched for on MRS (Oxoid) soil and incubated at 37 ° C for 48h. Finally for yeasts and moulds was used the Malt Agar soil (Oxoid) and the plates incubated at 30 ° C for 5 days.
For sensory analysis was used a group of 5 tasters operating within the DISAFA with a long experience in tasting..
Being unable to perform qualitative discriminating tests as they are of no use in monitoring shelf-life, we made a quantitative discriminating test, identifying the quality descriptors of the product and requesting the assessment using a 9-point hedonic scale (Figure 5).
The evaluation was completed by a question concerning the willingness to buy the product.
All products were tested anonymously and, except for the stuffed pasta, without any preparation. In the case of the stuffed pasta, this was of course boiled in Valmora natural water for about 2-5 minutes and without the addition of salt.
It was not possible to conduct a sensory examination of the puff pastry, as it would have required a preparation and then the use of other ingredients that could interfere on the characteristics of the product itself.
Figure 5 - Data used for the evaluation of satisfaction and willingness to buy the products in question.
Results
UHT milk
The tests concerned samples of semi-skimmed UHT milk branded Parmalat and Carrefour.
The following table shows the average composition and microbiological evaluation conducted during the conservation test.
It is evident that there are no significant variations in the composition and especially in the bacteria count correlated to the shelf-life.
The pH is about 6.5 with a slight difference between the two brands. A difference in colour is particularly evident where the product of brand n.2 has a colour with lighter shades due to lower values of red (a *) and yellow (b *).
With regard to the sensory test, the following table shows the average values attributed to the samples examined at the time of purchase and at the end of the storage phase.
In this case too, the storage does not set out significant variations in satisfaction and the purchase preference remains unchanged. The overall lack of satisfaction is due to the particular type of product (semi-skimmed UHT milk), which is not very aromatic and lack in fullness.
A slight difference between the brands about colour and general satisfaction perhaps is due to the too light amber colour characterizing the product of the 2nd brand.
The results provided by the electronic nose (Figure 6) show that the volatile profile of the two products do not changed significantly throughout the conservation, thus confirming the results obtained through the other physical-chemical or microbiological tests.
The profile of the two products is very different instead. The one of Brand n1 is irregular with very high values for the two sensors, 2 and 7. As for Brand n2 the profile is more regular very low intensity for all sensors. These differences relate to the initial corporate decisions and are not affected by storage.
Figure 6 - UHT milk profiles of the two brands assessed by electronic nose during storage.
Pasteurized milk
The tests concerned samples of pasteurized High Quality milk branded Abit and Centrale del Latte of Turin.
The following table shows the results of the composition and microbiological analysis carried out on products during storage.
The data do not show significant changes in the products during storage although in the case of the pasteurized milk of Brand 2 there is a light increase in the bacterial load that remains, however, within the limits.
The following figure (Figure 7) shows the volatile profiles obtained by the electronic nose.
Although the overall intensity of the signals supplied by the sensors appears very low and lower than that detected for UHT milks, there is a clear similarity between the two companies as well as the absence of differences attributable to the conservation, which confirms the results from both of composition and microbiological analysis.
Figure 7 - pasteurized milk profiles of the two brands determined by electronic nose during storage
With regard to the sensory test, the following table shows the average values attributed to the samples examined at the time of purchase and at the end of the storage phase.
These products, which are highly appreciated by the tasters, did not show significant changes during storage and the purchase preference remained unchanged even at the end of their shelf-life.
Diced cooked ham
The diced cooked ham samples tested were branded Carrefour and Beretta, the table below shows the results of the tests carried out during the storage.
For the samples of both brands there is an evolution for all the parameters considered, particularly for the lactobacillus amount, that operating with lactic acid production causes the consequent pH lowering. Not detected any parallel increase of coliforms, potentially pathogenic, so and the evolution of the product can be considered physiological, therefore acceptable. Being tested only two brands such behaviour cannot be standardised.
The profiles of the volatile component detected by the electronic nose (Figure 8) showed marked differences between the two products concerning both the structure of the profile and the intensity of the signal provided by the various sensors. In particular, the product of Brand n2 provides higher signals especially reaching the expiration date.
Figure 8 - cooked hams profiles of both brands detected by electronic nose during storage
The results of the sensory examination confirm those from the electronic nose, both regarding the differences between the brands (less welcome are the products of brand n2 ), and the evolution of volatile component for product 2 .. Satisfaction and purchase preference, when compared to other products, diminish during storage, even though remaining completely acceptable.
Puff Pastry
The tests related to the Carrefour brand of puff pastry samples, the table below shows the results of the tests carried out during storage.
The product shows no significant changes in colour, as highlighted by both the CIELAB and the DE values, which remains inferior to 3 for the entire storage period, as well as in the content in active water.
Even the bacterial count does not present significant changes.
This constancy does not seem to find confirmation from the point of view of the volatile fraction assessed by the electronic nose (Figure 9), but it should be noted, for this product, that the evaluation was made directly on the package, and it could be affected by the modified atmosphere and /or the polymer of packaging.
Figure 9 - cooked hams profiles of both brands detected by electronic nose during storage
In the following illustration (Figure 10) is finally given the diagram of the texture strength test carried out on the pasta with the Texture Analyser.
The curve analysis allows to identify three characteristic values of the product i.e. the maximum resistance to penetration (A; in N), the penetration energy corresponding to the area under the curve (B; in mJ) and the adhesiveness namely the area of the negative curve (C, in mJ).
Figure 10 - Profile of texture strength for the puff pastry detected through Texture Analyser (A-maximum resistance to penetration, B-energy penetration; C-adhesion)
In the box-plot below the values are measured according to the shelf-life do not show significant changes due to storage (Figure 11).
Only adhesively undergo a slight increase from the sixth day of shelf life.
This, together with changes in smell and a lowering in the sensors signal, suggests a growing permeability of the packaging polymer through time with consequent leakage of the modified atmosphere and humidity intake.
Figure 11 - Evolution of the structural parameters during storage of the puff pastry
Fresh stuffed pasta
The tests were conducted on the tortellini with meat filling branded Buitoni and Carrefour and the following table shows the composition and microbiological evaluation conducted during the conservation.
There is a slight increase of the bacterial count in both products at the end of the storage phase with a correspondent slight lowering in the ph. Being a pasteurized product this is a normal occurrence, especially considering its long shelf-life, and it has no particular effects on the consumer being eaten only after cooking.
From the point of view of the volatile component, the sensory profile is structurally similar between the two brands but with a significant difference from the quantitative point of view (Figure 12) due to the different composition of the two products.
Figure 12 – Profiles of both brands of puff pastry detected by electronic nose during storage
The evolution of the bacterial count presents a feedback in the level of the volatile fraction with a signal increase of almost all the sensors in correspondence of the samples at the end of shelf-life.
From a sensory point of view the two products are both pleasing, while a slight preference is given to brand 1. Purchase preference is given to both even past its shelf-life. It should be noted that the product was consumed after cooking and therefore the effect of the bacterial count is not detectable.
Yogurt
The tests covered strawberry yogurt branded Yomo.
The table shows the results from composition and microbiological analyses carried out on samples of strawberry yogurt during the storage phase.
Evidently the composition is constant during the whole storage period, with a slight loss of red component (a *)and a corresponding increase in the yellow component (b *) in the last stage of the shelf-life. This leads to an increase in the DE value, however significantly lower than 3, that is the hypothetical limit to the human visual perception.
It should be noted that this phenomenon is a regular occurrence and is due to a degradation over time of the red anthocyanin pigments of added fruits (strawberry) due to the acidity of the product.
Equally regular is the reduction in the bacterial count that is observed during storage and which remains, though, higher than the limits imposed by law even at the end of its use-by date.
This maintenance of compositional and microbiological characteristics is confirmed by the volatile fraction detected by the electronic nose that shows a perfect overlap of such profiles during the storage of the product (Figure 13).
Figure 13 - Profiles of yogurt determined by electronic nose during storage
From the sensory point of view the product was satisfactory in all its aspects, even at the end of its shelf life with a high purchase preference.
Conclusions
The results from the study show that almost all the examined products, during their period of shelf-life fixed by the manufacturer, while undergoing a more or less distinct chemical-physical, microbiological and consequently sensory change, keep their composition characteristics practically unaltered through time, with a high satisfaction rating and purchase preference.
Such changes are closely related in the first place to the manufacturer and so to the different manufacturing techniques. Secondly they are obviously related to the type of product, and then to its greater or lesser durability (a UHT milk is more durable than a pasteurized one because of the different heat treatment, a yogurt is very durable because of its high acidity and so on).
Only for the diced cooked ham was found a significant change in the lactobacillus count for both the considered brands.
Since there is no bibliography on this product, it might be necessary to further study it to clarify whether the observed changes have to be considered a coincidence, limited to a few brands, or if it they are a regular occurrence related to the particular type of product.
It must be finally noted that the positive results of the study are due to the products perfect storage conditions, which are essential in the preservation of their compositional and sensory characteristics even at the end of theit shelf-life.
Bibliography
- Smil V. (2004) Improving efficiency and reducing waste in our food system. Environmental Sciences, 1, 17-26
- Segrè R., Falasconi L. (2011) Il libro nero dello spreco in Italia: il cibo. Ambiente Edizioni, Milano.
