Processing of fruits or vegetables can improve sustainability factors like shelf life (e.g. freezing or juicing) or reduced shipping weight (dry powders), but many nutrients are sensitive to heat and oxidation that these processes can introduce. In this article, we look at how processing can impact nutrient content and ways we might reduce that impact to balance nutrition with sustainability in the future.
Key dietary shifts are emerging through a collaboration of food science and nutrition with the aim to couple reductions in both our carbon footprint and risk of chronic disease, helping to build a sustainable healthy future for us all.
According to online data base, Our World in Data, in 2019 74% of global mortality was attributed to chronic disease, with CVD (cardiovascular disease), cancer, and diabetes the main contributors. Our eating habits and the associated increase in obesity worldwide being a primary cause of these statistics. At the same time Board Bia share statistics on food waste indicating over one third of all food produced in a year is wasted, contributing to almost 10% of global GHG (greenhouse gas) emissions and losses of €1.2 trillion each year. This highlights the potential for food science and nutrition in preserving our future, and there are some exciting dietary innovations already out there.
Nutrition of berry fruit
A shift from western dietary patterns consisting of red meats and processed foods high in saturated fat, sugar, and salt to the flexitarian style diet consisting of whole foods like fruits, vegetables, grains, pulses, and oily fish is becoming increasingly popular. These are more nutrient dense high fibre options, but many of these foods contain non-nutrient compounds that have potential health benefits called phytochemicals.
Regardless of fresh or frozen, in the case of berries, they possess a nutritional edge due to their phytochemical composition which has been quantified in numerous studies (Toledo-Martin et al. 2018 and Ponder et al. 2021). Phytochemicals such as polyphenols, anthocyanins, stilbenes, and carotenoids along with essential vitamins and minerals are found in common house-hold berries such as blueberries, blackberries, strawberries, and raspberries. Lesser common berries such as Sea Buckthorn and Mulberry are composed of the same phytochemicals. These compounds have been shown to have anti-inflammatory and antioxidant properties that have linked them to different parts of health.
Berries as Antioxidants
The high antioxidant activity of berries due to their phytochemical concentration means they help to effectively scavenge unwanted oxidizing radicals from our body. These oxidizing radicals are thought to be linked to development of different diseases and health conditions, and may be one way berries work to improve health (Soobrattee et al, 2005).
Studies have shown phenolics such as ellagic acid present in these berries may protect against atherosclerotic plaque formation in our blood vessels, reducing the risk of hypertension and heart disease (Olas et al. 2008). In 2015, the PREDIMED study concluded increased polyphenol intakes were associated with reduced blood pressure in trial participants as well as decreased biological markers of inflammation and oxidation, possibly contributing to reduced risk of cardiovascular disease.
Blood sugar management
Clinical trials in humans have shown the anthocyanins and stilbenes found in these berries may reduce the impact of postprandial hyperglycaemia (sugar spikes after a meal), which could protect cells of the pancreas and liver from oxidative stress and inflammation, leading to a potential reduction in the risk of type 2 diabetes (Blaak et al, 2012).
How does processing impact berry nutrition?
For many people, fresh berries are the preference when it comes to taste and texture, but these non-climacteric fruits have poor shelf-life. Within a couple of days to a week, berries enter senescence and mould begins to grow. For this reason, freshly purchased berries are often thrown in the bin and this is a primary example of the food waste that contributes to significant GHG emissions.
Food scientists have looked at several berry preservation methods to prolong their naturally short shelf-life, but there is often a caveat associated with the properties of processed food.
Thermal processing (dried berries), which aims to reduce the moisture content of the berries, will successfully extend shelf-life but causes leaching of certain nutrients and phytochemicals (Figure 1) which negatively impacts the nutritional value of the berries.
Juicing berries has also been a successful processing method in extending shelf-life, but this too causes a reduction in desirable phytochemicals such as anthocyanins. These conventional processing methods are effective, but we need to think outside the box to make our food systems more sustainable. Shelf-life and nutritional integrity must be optimised.
Freezing or freeze drying provides fruit and vegetable products with a variety of economic and environmental benefits.
We don’t have to worry about losing nutritional value if we opt for frozen berries. Studies have shown berries maintain a complete nutritional profile after freezing (Lohachoompol et al, 2004) unlike other thermal processing methods. This means shelf-life is improved without compromising nutritional profile which we now know is of great value in berries.
The economic and Environmental Benefits
There is no need to bin frozen berries a few days after they’re bought, immediately ruling out food waste. As well as this, Frozen fruit can be, and usually are sold in larger volumes of up to 1kg due to improved stability post freeze-drying, compared to fresh berries which are usually sold in trays of 100g to 300g. If we were to switch to frozen berries, this would significantly reduce the amount of plastic packaging required which is another crucial aspect of sustainability.
The fresh berries we buy often contain stems and leaves, otherwise known as ‘cut-offs’. These cut-offs are usually thrown to waste in the home. However, innovative industries are now using cut-offs from fruit & vegetables going through the freeze-drying process to generate biogas through anaerobic microbial digestion, providing energy in a circular manner which is further reducing the waste generated from frozen fruit and vegetable production (Carlos Morales-Polo et al, 2019).
For consumers, there is also economic value to frozen berries. At one popular international grocery store, fresh berries cost between €10 & €20 per kg compared to frozen berries at approximately €3 per kg, indicating a significant cost-saving associated with frozen berries.
Freeze drying can strike a balance between sustainability and nutrition, making it a promising tool to consider for the future food system.
Paraic Reville, BSc
Paraic Reville (BSc) graduated with a BSc in Nutritional Sciences from University College Cork and is currently completing a MSc in Clinical Nutrition & Dietetics at University College Dublin. Research interests lie in antioxidant and anti-inflammatory potential of food, sustainable nutrition, and dietary modulation of chronic disease.
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