Nutrient Loss in Vegetables After Storage
Vegetables are known for their valuable sources of health-promoting vitamins, minerals and fibre. Other than that, phytochemicals in vegetables, such as polyphenolics, carotenoids and glucosinolates also have their nutritional value needed for human well-being. Thus, vegetables are often one of the main components appeared in healthy diet as suggests by many nutritionists.
The main purpose of eating fresh vegetables is to get the nutrients essential for our health. However, most of the times we don’t really eat vegetables that are truly fresh. They might look fresh on the outside but in fact they have been stored for several days or weeks after harvest. The nutritional content of these aged vegetables is no longer at its peak just as the time they were harvested.
If we don’t get the most nutrients from vegetables because they are not fresh, why are we still eating vegetables? This misaligns with our initial purpose of eating fresh vegetables to get the most nutrients out of them for our health benefits.
How to define fresh vegetables? We’ve explained in detailed the term “fresh” and discussed the factors that decide food freshness in our previous blog.
Food Loss and Food Waste
Have you ever discarded wilted vegetables several days after you purchased them from grocery shops? Why are these leafy greens turning yellow and wilted so quickly even after you stored them in the refrigerator? This is most probably because of the transportation time taken after the vegetables were harvested. Sometimes, you will notice the imported vegetables wilt quicker than the local ones because the former was shipped thousands of kilometres away from the countries of origin.
This problem is faced by not only household consumers, many restaurants and hotels are also having the similar problem. They discard even more vegetables that are not fresh because these organisations need to provide food safe for eating and food that can fulfil the sensory experience of their customers.
According to the Food and Agriculture Organisation of the United Nations (FAO), it was estimated that 32% of all food produced in the world was lost or wasted in 2009. In other words, up to one third of all food is spoiled or squandered before it is consumed by people.
The world is already facing food shortage and the problem will be getting more severe as world population grows and due to climate change. If food loss and food waste persist, it will contribute to food scarcity. Therefore, with the advent of technology, urban farming, vertical farming and indoor farming have become the new alternatives to address the issues of nutritional and quality losses of the leafy greens.
Quality of Vegetables Changes During Storage
The loss of nutrients in our greens is often linked to transport and storage. An article published by LDL Health revealed the significant nutrient losses in vegetables during refrigeration.
In as little as 16 days, freshly harvested green beans had lost 90% of its ascorbic acid (Vitamin C). Spinach loses 22% of lutein and 18% of beta carotene content after just eight days of cold storage whereas lettuce loses 46% of some key nutrients within seven days of cold storage. Vitamin C is an important water soluble nutrient which among other things plays a role in immune function and collagen production. Lutein is an antioxidant that has been linked to eye and heart health.
As for culinary herbs, when used fresh, contain significant amounts of antioxidants. These antioxidants decrease rapidly after harvest making it difficult to reap the full health benefits of fresh culinary herbs with products from commercial grocery shops.
In order to provide more evidence on quality drops over a period of storage time, scientists have conducted experiments on Valeriana lettuce stored at 4 or 10 °C for 15 days.
The results showed that the higher storage temperature affected the lettuce leaf quality. Significant chlorophyll reduction in leaves was observed after only 5 days of storage at 10 °C while total carotenoids were found to decrease significantly after 8 days of storage at both 4 °C and 10 °C. Anthocyanin and total phenols did not change statistically during the entire experimental period.
Another group of researchers also performed storage experiments on leafy vegetables such as spinach and lettuce harvested at commercial stage and stored at 4 or 10°C. The findings indicated that chlorophyll, carotenoids and phenols did not change in both species after 6 days of storage at both temperatures but ascorbic acid declined during storage. The decrease was more significant in lettuce than in spinach.
Even if some quality parameters were stable during the 6 days of storage, the decline of ascorbic acid suggests, at least for lettuce, it is better to consume within 6 days after harvest in order to get the most nutrients out of this vegetable for health benefits.
These are just a few examples of how plants steadily lose nutrients while being stored, even at optimal temperatures. While grocery shops produce may be aesthetically pleasing, the fact is the nutrient content is often times low comparatively speaking.
In addition to transport and storage, harvesting vegetables before they are fully developed can contribute to low nutritional content. A vegetable is said to be ripe once it has reached full development and is ready for harvesting. Due to the nature of commercial agriculture, produce can sometimes travel great distances before it reaches its destination – your neighbourhood grocery shops. It means that sometimes a plant must be harvested before reaching a fully developed stage so that it may have a longer shelf life.
This practice decreases the nutritional content of vegetables because it takes a certain period of time for nutrient uptake in plants but they are harvested before the nutrients are fully absorbed by the plants. As a result, the nutritional content in the plants is comparatively lower than the plants harvested at its maturity.
In brief, before a vegetable makes it to your dinner plate, it has likely lost a considerable amount of its nutrients.
Vegetory Delivers Fresh Produce Within a Day
This is where Vegetory comes in to provide the consumers with vegetables that are truly fresh. As a local urban farmer, Vegetory harvests all its greens when they reach the fully developed stage and delivers the fresh produce to its consumers within a day.
We guarantee the freshest vegetables and herbs that contain the nutrients at its peak so that our consumers can reap the health benefits from these vegetables. Our greens are all grown hydroponically in a clean and controlled environment. Thus, they are completely free of pesticides.
Be sure to look for Vegetory if you want your family to have the freshest and most nutritious greens.
Author: Christine S.H. Lee