Sensorial degradation in green coffee can represent significant financial losses for producers, traders, and roasters. Yet while a certain degree of degradation over time may be inevitable, the material of the coffee packaging can have a significant impact on the shelf life and quality of the beans.
Jute, high-barrier, vacuum: which is really best? How much of an impact does the material actually have on the beans? And how can we measure this? Let’s take a look.
Lee este artículo en español Material Del Empaque: Cómo Afecta al Café Verde Con el Tiempo
An empty, used jute bag with moisture stains. Credit: Ivan Petrich
Reviewing Green Coffee Packaging Materials
Some of the most common materials are burlap, permeable plastic, high-barrier plastic, and vacuum.
A canvas made from natural fibres extracted from plants, jute or burlap is the most traditional material used for manufacturing coffee bags. It’s an eco-friendly option; the Food and Agriculture Organization of the United Nations says that it is “100% bio-degradable and recyclable and thus environmentally friendly.” It’s also durable and relatively affordable, being the oldest coffee packaging material to date.
However, it doesn’t provide protection against moisture or oxygen – two elements associated with poorer coffee quality and even defects such as mold. The bags are permeable.
Moreover, jute bags traditionally hold 60 kilos of coffee (or, in some countries, 70 kilos). Meanwhile, plastic big bags and container liners can store from 1 to more than 20 tons of green beans. Depending on the lot being stored or shipped, producers may decide to opt for larger and therefore more efficient storage options.
Most commonly made of polyethylene or polypropylene, plastic storage options range from 60-kilo bags to big bags and container liners. The material is cheaper and more resistant to moistures and gases than jute but is still permeable.
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Green coffee beans stored in a plastic fabric coffee bag at Cerro Verde, El Manilal, Nayarit, México. Credit: Ana Valencia
Professor Flávio Meira Borém is an agronomic engineer specialized in vegetable production. He has dedicated the past few years to studying coffee. He says that a high-barrier bag is “a pack with different compositions and structures which are capable of preventing gas and water exchanges between the inside and the atmosphere… It’s packaging with high impermeability.”
While more expensive than other types of packaging, a high-barrier bag is designed to maintain the coffee’s quality over time by preventing chemical reactions with moisture and oxygen. You can find high-barrier packaging in a range of sizes, including container liners.
High-barrier Videplast bags in use at Fazenda Klem. Credit: Nicholas Yamada
When coffee is vacuum packed, it is also stored in impermeable plastic bags. Then, in addition to the hermetic isolation of the green coffee, a negative pressure is then created to remove all air.
It’s a common belief that multi-laminate vacuum-packing is the most effective way to preserve green coffee quality. However, with a considerably higher cost, this method is typically only used for samples or micro and nano lots of exceptional specialty coffees.
Vacuum-packed green coffee samples. Credit: Ivan Petrich
Defining Coffee Degradation
Coffee degradation is the chemical changes that result in reduced flavors and aromas in the beans, especially sweetness and acidity. Cupping by a professional Q grader according to SCA protocols remains the most common way to measure coffee quality. Yet there are other ways to track degradation.
Some of these focus not on the sensorial qualities you can notice when drinking the coffee but instead on the chemical composition of the beans and how that relates to their cup profiles. While this is a relatively new field, these studies allow us to better understand degradation even before it becomes evident to the human tongue and nose. Nuclear magnetic resonance (NMR) and Raman spectrometry are two methods used for this.
Giselle Figueiredo Abreu is an agricultural engineer and the author of “Raman spectroscopy: A new strategy for monitoring the quality of green coffee beans during storage,” which she published as part of her post-graduate work, overseen by Prof. Borém.
Abreu crossed-referenced sensorial reports from Q Graders with the results from Raman spectroscopy, and used this to analyze green coffee stored in permeable and impermeable packaging over time.
The coffee samples were of natural and pulped natural coffees cupping at over 84 points. Three types of 30-kilo containers were used: permeable paper packaging without a barrier, paper packaging with an impermeable high-barrier plastic bag inside, and vacuum packaging. The coffees were analyzed every three months for 18 months.
A high-barrier big bag developed to hold up to 1,200 kilos. Credit: Videplast
The Impact of Bag Material, 0–6 Months
According to Prof. Borém, in the first six months, the Q graders weren’t able to identify significant differences in the cupping scores for either naturals or pulped naturals, regardless of the choice of packaging. He says, “Cuppers have a very small likelihood of detecting sensorial differences in specialty coffee in the first 6 months. The possibility is very small, the differences are slight.”
But he stresses that the chemical composition was visible at both three months and six months, when they used both NMR and Raman spectrometry, for samples stored in permeable bags. Samples stored in impermeable bags, however, did not have visible evidence of any chemical changes.
“We were able to prove that the chemical composition of coffee begins to change early on, and this change will only be noticed by the cuppers after six months of storage,” he explains.
“This change is irreversible,” he stresses.
Although cupping scores might not show a difference between permeable packaging, such as jute bags, and impermeable high-barrier packaging, it’s clear that the beans are already beginning to degrade.
Leandro Martinoto is P&D Manager at Videplast, a packaging manufacturer with a focus on specialty and fine coffees. He tells me, “We recommend that after processing, coffee should be stored in multi-laminated high-barrier structures. These can be big bags, regular sacks, or liners.”
Prof. Borém also recommends that for specialty naturals and pulped naturals, “after the resting period… this coffee should already immediately be protected with a high-barrier bag.”
Within the warehouse, big bags and high-barrier liners will help conserve space and reduce costs. For smaller lots and for transportation, high-barrier bags are preferable to jute bags.
Green coffee inside a Videplast high-barrier bag. Credit: Nicholas Yamada
The Impact of Coffee Bag Material, 6–18 Months
After six months, cupping scores for coffee stored in permeable packaging started to fall. Prof. Borém says, “The sensory difference is already striking.”
He points to a pulped natural coffee originally cupped at 85–86 points and stored in permeable packaging. At nine months, it was cupping below 80 and considered commodity coffee. After 18 months, the coffee fell to below 75. In contrast, in the impermeable bags, it was still cupping at 83–84 points a year later, before dropping to 82 points after 18 months.
As for the different types of permeable packaging – high-barrier and vacuum-packing – the study only found negligible differences.
Unlike in the first six months, processing had a significant impact at this stage. Prof. Borém tells me, “These changes were more evident in the natural coffee than in the pulped natural.”
While it’s recommendable that specialty coffee is stored in impermeable bags straight after storage (the same applies for fine cup coffees), after six months, it becomes imperative. This is particularly true for coffees dried with some or all of the fruit still attached to them. Naturals are particularly vulnerable to degradation.
It is also worth remembering that the study was based on coffees in a stable environment. Coffees being transported, especially those going overseas, may be exposed to greater degrees of humidity. They will be at higher risk of degradation without the protection given by impermeable packaging. Container liners may also help to mitigate this risk.
Read more in Why Specialty Naturals Need Strict Quality Control
Green bean samples. Credit: Battlecreek Coffee Roasters
When it comes to specialty coffee, preserving the beans’ quality for as long as possible is essential. Doing so can protect the value of the coffee as well as the business relationships formed between producers, traders, and roasters. Paying attention to bag material, especially for natural and pulped natural coffees, can significantly reduce bean degradation over time.
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Written by Ivan Petrich. Feature photo: Green coffee in jute bags. Feature photo credit: Neil Soque
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