When it comes to packaging, many farmers don’t spend much time thinking about it. At least that is what I have experienced in the past. Most of them just look at what other farmers are using and stick to it. While this seems to make sense, it often doesn’t.
Mainly because new mushroom farmers don’t know the context in which a specific packaging is used by these farmers. But that’s sometimes true for seasoned mushrooms farmers too.
There are three main reasons for packaging
- Protection
- Branding
- Marketing
While the two topics branding and marketing are very interesting in this article I will only address protection.
PROTECTION
Why do we want to protect our mushrooms in the first place? To answer this question, I listed below a non-exhaustive list and in no order:
- If you are growing mushrooms or want to grow them, you deal with highly perishable produce which needs protection against mechanical, fungal or microbial damage. All of them are reasons for deterioration.
- Mechanical damage is caused throughout the whole process. Starting with harvesting, cleaning, packaging, storage, and transportation.
- Fungal and microbial damage is caused by changes in temperature, humidity, and/or the composition of the air atmosphere surrounding the product.
- Mushrooms contain up to 98% water.
- Mushrooms last roughly only 1-3 days @RT[1].
- If the temperature is too high (> 5°C), water loss is the result. The mushroom losses weight and quality.
- If the temperature is too low (< 0°C), injures from freezing is the result.
- High temperature increases the microbial load on the mushrooms.
- As a rule of thumb for every 10°C over the optimum temperature for the specific mushroom species the biochemical activities will increase by 2-5-fold and vice versa.
- If the relative humidity does not meet the respiration rate of the mushroom water loss and therefore, a decline in quality is the case.
- At high relative humidity the growth of microorganisms is accelerated.
- All fresh produces are still alive after harvesting. This is especially true for mushrooms. Which means the biochemical processes are still ongoing.
- All fresh produces are sensitive to the concentration of oxygen and carbon dioxide.
- If the oxygen concentration is too high, (> 10%) oxidation of the tissue is happening (browning).
- If the oxygen concentration is too low (< 1-2%), the process switches from aerobic to anaerobic.
- O2 & CO2 concentration, temperature, and humidity are having an influence on the respiration rate and the transpiration rate of the mushroom. What is respiration rate? Respiration is a metabolic process that provides the energy for plant biochemical processes. What is transpiration rate? Transpiration rate is the amount of water which a living organism releases under certain conditions into its environment.
- The ratio of CO2 produced to O2 consumed, known as the respiratory quotient (RQ), is typically assumed to be equal to 1.0 if the metabolic substrates are carbohydrates.
- It was found an RQ of approximately 1 for mushrooms at 10°C and at O2 levels greater than 1-2.5%. Below this O2 level, RQ increased rapidly to a value higher than 6.
Wow, that is a long list. Did you know all these things? Let me know.
Let’s go a step further and look at the impact of temperature and humidity level on the transpiration rate (Figure 1). Here we can clearly see that the lower the humidity level the effect of the temperature increases and vice versa.
Figure 1: Effect of storage temperature and relative humidity on transpiration rate of mushroom[2]
As mentioned before, at certain conditions, microorganisms are growing. But it is important to know that even fresh-cut mushrooms have already a high load of microorganisms on their surface.
This makes a careful handling necessary. Because of this high load of microorganism, a pre-packaging process is needed. This pre-process starts already during the growing phase and contains a total of four steps.
- Irrigation[3] with inhibitors during the grow phase
- Trimming[4],
- Pre-Wash[5] and
- Washing[6] with inhibitors plus Drying.
If you want to learn more about these four steps and their impact on your mushrooms, I put some detailed information together in my article Mushroom Shelf Life: 8 Bests Practices to Extent It!
CUSTOMER
If we think about packaging our customer comes into play. Depending on the type of customer you serve, the packaging may change (Table 1). The reason for that is a) easy handling, b) reusability, c) storage possibility, and d) perceived value.
| Customer | Packaging size (examples) | Packaging material (examples) |
| Farmers market | 0.5 lb | Paper, Styrofoam |
| Restaurants | 5 lb to 10 lb | Plastic box |
| CSA | 10 lb to 20 lb | Carton box |
| Retail | 0.5 lb | Styrofoam, Plastic wrap |
Table 1: Examples of packaging sizes and packaging material depending on the customer type[7]
MATERIAL
Let’s investigate some of the materials more in detail to understand better their advantages and disadvantages.
Paper
Table 2: Overview of the characteristics of paper[8]
Plastic
Table 3: Overview of the characteristics of paper[9]
As you saw, both packaging materials have their pros and cons (Tab. 2 and Tab.3). You have to think about which of the aspect quality, safety, ecologic, or economy is important for you and especially for your customers.
MUSHROOM QUALITY
When it comes to selling mushrooms, the main indicators for your customers if they are fresh in their appearance. Figure 2 gives an interesting overview of different fungi (here Champignons) and their appearance.
Category 1: Fresh white Champignons with light pink slats with superficial, slight brownish discoloration.
Category 2: Fresh brown Champignons with pink to light brown slats.
Category 3: Overlayered white, soft Champignons with brown spots on the cap, open and black slats.
Category 4: Spoiled brown Champignons with brown stems, moist, soft (open) and black slats.
Category 5: Spoiled white Champignons, soft, brown discolored inside, moist.
Category 6: Spoiled white Champignons with inside brown discolored stem and cap, with black slats.
Figure 2: Classification of button mushrooms (Champignons) according to their appearance[10]
In my article 26 Delicious Mushroom Species You Should Cultivate I give you an overview of a variety of mushrooms, which mushroom farmers are growing and selling.
MODIFIED ATMOSPHERE/HUMIDITY PACKAGING
After this introduction, I want to address some developments in the area of packaging. To do so, I will first introduce to you the concept of modified atmosphere/humidity packaging (MAP/MHP).
The idea behind these packaging is to control the atmosphere and therefore, humidity inside the package. The basic principle of this concept is shown in figure 3. While the tray seems normal, it isn’t. Inside the Styrofoam is a layer of hygroscopic salt (Fig. 3 red line). This salt will absorb the moisture inside the package and therefore reduce the amount of water inside of it.
Figure 3: Concept of an active tray with NaCl[11]
In figure 4, you can see a comparison of two trays – one with no salt (Fig. 4 left side) and one with salt (Fig. 4 right side). With the new package, it could be shown that the is no condensation after 2 days and 8 days on the permeable film (Fig. 4 right side).
Figure 4: Active Packaging, left after 2 days and 8 days (no salt), right after 2 days and 8 days (with salt)[12]
While we could not see in figure 4 clearly the change in the appearance of the mushrooms, figure 5 does. On the left side (a) we see mushrooms that were stored in a standard PP tray for 6 days at 7°C. Here the caps are already open, and we see a lot of browning going on.
If we compare them with the right side (b) the caps are still closed, and the discoloring is way smaller. These mushrooms were stored in a humidity-regulating tray.
Figure 5: Appearance of mushrooms stored for 6 days at 7°C; (a) controll-PP tray, and (b) humidity-regulating tray[13]
But if we deal with the moisture content within the packaging, we have to think twice. Because on the one side, our mushrooms have a high moisture content 90+% RH, but at the same time in this environment, fungi, yeast, and bacteria are growing (Fig. 5. No. 10 – green area).
Figure 5: Impact of the humidity on the quality of products[14]
Because of this situation, researchers investigate different possibilities to avoid it. One example is the use of sorbitol (Fig. 6 and Fig. 7). Figure 7 shows promising results. Here the active foil (with sorbitol) reduced the number of bacteria on the test object (here cheese).
Figure 6: Storage of cheese in a package with Sorbitol (test set-up)[15]
Figure 7: Results of the test – Cheese in a package with Sorbitol; green: starting values, pink: values after 24h, yellow: values with sorbitol[16]
SUMMARY
Choosing the right packaging material is not an easy task. Many things have to be considered, especially if you want to provide high-quality mushrooms to your customers. In essence
- If followed these procedures the shelf life can be extended up to 14 days[17]. It is fair to say that this extension can only be achieved under ideal conditions.
- Especially the handling of the retailers is still, to some extent, a black box. It is, therefore, necessary to compensate/address the possible events which can happen at these sites. This helps to make sure that the customer receives a high-value product that will not harm him.
Storage and Transportation of your mushrooms are part of the best practices in mushroom cultivation. If you want to learn more about these practices you should read this article. In it, I will talk about eight common best practices which will help you to extend the shelf life of your mushrooms and, therefore, give your customers a better experience.
[1] RT: room temperature
[2] Guido Rux (2015) Application of humidity-regulating tray for packaging mushrooms
[3] R.B. Beelman (-) Selected Cultural and Harvest Practices to Improve Quality and Shelf Life of
Agaricus Mushrooms
[4] Said O. Ajlouni (1992) Stipe Trimming at Harvest Increase Shelf Life of Fresh Mushrooms
(A. bisporus)
[5] G. M. Sapers (2001) Shelf-Life Extension of Fresh Mushrooms (A. bisporus) By Application of
Hydrogen Peroxide and Browning Inhibitors
[6] G. M. Sapers (2001) Shelf-Life Extension of Fresh Mushrooms (A. bisporus) By Application of
Hydrogen Peroxide and Browning Inhibitors
[7] Own table
[8] Own table based on Source
[9] Own table based on Source
[10] Source
[11] Guido Rux (2015) Application of humidity-regulating tray for packaging mushrooms
[12] Sven Sängerlaub (2012) Aktive Verpackungen – Aktueller Stand der Entwicklung und Nutzen für Lebensmittel
[13] Guido Rux (2015) Application of humidity-regulating tray for packaging mushrooms
[14] Sven Sängerlaub (2012) Aktive Verpackungen – Aktueller Stand der Entwicklung und Nutzen für Lebensmittel
[15] Sven Sängerlaub (2012) Aktive Verpackungen – Aktueller Stand der Entwicklung und Nutzen für Lebensmittel
[16] Sven Sängerlaub (2012) Aktive Verpackungen – Aktueller Stand der Entwicklung und Nutzen für Lebensmittel
[17] Preeti Singh (2009) Recent advances in extending the shelf life of fresh Agaricus mushrooms: a review
