Preserving Nutrition In Long-Term Food Storage

People cultivate gardens for a variety of reasons. Some seek a connection with nature and a chance to relax, while others embark on gardening endeavors to cut down on grocery expenses or minimize their trips to the store.

Personally, I find joy in strolling into the backyard and selecting vegetables for dinner based on what’s ripe and ready, rather than meticulously planning meals for an entire week.

My spouse actively participates in gardening because there’s an undeniable difference in the taste of freshly harvested, sun-ripened produce. Those with a focus on health grow gardens to enhance the nutritional quality of their produce, ensuring they harvest at the peak of ripeness.

These advantages, however, are fleeting and only endure for a few months unless you take steps to preserve your harvest. The question then arises: how does the process of preserving affect the nutritional value of the food?

Fresh Food Advantages

To begin, let’s delve into the nutritional excellence of fresh, unprocessed food, rich in both macronutrients and micronutrients. Macronutrients, encompassing proteins, carbohydrates, and fats, are intricately structured and resistant to significant changes, save for the breakdown of starches or the denaturation of proteins under high heat.

Our main focus here shifts to micronutrients—minerals, vitamins, and phytochemicals. Minerals, elemental and inorganic, such as calcium, iron, and magnesium, are sourced by plants from the soil they inhabit, absorbed as they take in water. The nutritional value of plants is directly influenced by the health of the soil they grow in.

In contrast, vitamins, crucial organic substances that our bodies cannot produce, are synthesized by plants, becoming available to us upon consumption. Phytochemicals, another class of micronutrients, though less researched due to their complexity, hold potential health benefits for humans. Originating from plants, these chemicals may function as antioxidants, boost immunity, facilitate cellular communication, neutralize carcinogens, induce apoptosis in tumor cells, and repair damaged DNA.

Continual research aims to unravel the identities and roles of phytochemicals. These compounds, produced by plants as a natural defense against sun damage, insects, drought, and microorganisms, also contribute significantly to the flavor and color of the produce we consume.

Influential Factors on Nutritional Quality

Optimal nutrition is often associated with fully ripe, but not overripe, produce, as it boasts the highest nutritional content. Among the essential components, Vitamin E, a collection of eight fat-soluble compounds with uniform functionality in the human body, reaches its peak levels at optimal ripeness. Fascinatingly, in the case of peppers, researchers observed an increase in vitamin E content as chlorophyll degraded, a process that coincided with the peppers’ color becoming more pronounced.

While it might seem like a gloomy outlook, the impact of food processing on nutrition isn’t entirely negative. Some nutrients undergo a positive transformation, becoming more bioavailable, meaning they can be better utilized by the human body, through the cooking or processing of food.

This phenomenon is particularly noteworthy for phytochemicals, as the heat generated during processing disrupts their cellular matrix, facilitating easier digestion and nutrient absorption. Notably, certain foods that exhibit increased bioavailability post-cooking include spinach, carrots, and sweet potatoes.

In addition to specific phytochemicals, minerals such as iron, calcium, and potassium also become more readily digestible when the vegetables containing them are subjected to cooking processes.

Understanding these intricacies not only sheds light on the dynamic relationship between food processing and nutrition but also emphasizes the importance of discerning the ripeness of produce for optimal health benefits.

Impacts of Temperature on Nutritional Content

Conversely, water-soluble vitamins exhibit a remarkable sensitivity, making them susceptible to degradation. Elevated temperatures from cooking or processing often result in the deterioration of these vitamins, leading to a reduction in their presence in food. Notable examples include vitamin C and the B vitamins, such as thiamin, riboflavin, B6, and folate (with the exception of vitamin B12, synthesized by certain bacteria and not prevalent in most plant products).

The consequence of high heat on a food’s vitamin C content can be substantial, with reductions of 50% or more. Some studies propose that canning might lead to a staggering 90% decrease in vitamin C levels in certain vegetables. Heat exposure also presents a challenge to the stability of B vitamins in produce, potentially causing losses ranging from 10% to 70%. However, it’s worth noting that a portion of these vitamins typically leaches into the aqueous solution where the food is stored.

Root vegetables, when subjected to canning heat, experience losses in phosphorous, thiamin, beta-carotene, beta-cryptoxanthin, lycopene, lutein, and zeaxanthin in the range of 10% to 20%. Folate and vitamin C show reductions of 20% to 25%. For other vegetables, vitamin C, thiamin, and folate losses tend to fall within the range of 10% to 15%.

Interestingly, tomatoes exhibit lower nutrient loss due to heat, primarily because they are often processed in a hot water bath, facilitated by their high acidity, as opposed to pressure canning. The primary losses are observed in folate (70%) and choline (10%). Raw tomatoes, however, are considered rich sources of vitamin C, potassium, folate, and vitamin K.

Certain nutrients, such as niacin, pantothenic acid, and biotin, demonstrate greater stability in heat. Minerals like calcium, magnesium, iron, sodium, zinc, and copper remain unaffected by heat, maintaining their content in food even after heat processing. Any observed mineral loss in canned food is likely attributed to minor leaching by the processing water.

For low-acid foods undergoing pressure canning, where temperatures of 240 to 250 degrees Fahrenheit are required to eliminate Clostridium botulinum spores, vitamin loss becomes inevitable due to the high heat involved in the process.

The Impact of Canning Medium on Nutrition Retention

Water-soluble vitamins have a tendency to dissolve into the canning medium, the liquid environment in which produce is preserved and stored.

Root vegetables, known for their richness in potassium, folate, manganese, vitamin C, beta-carotene, and various B vitamins, experience not only losses during the heat of processing but also an additional leaching of 10% to 15% of vitamin C, thiamine, and folate, along with select minerals, into the canning medium.

Other vegetables undergo an additional 10% loss of vitamin C, thiamin, and niacin, with a 20% reduction in folate. Beta-carotene, lycopene, lutein and zeaxanthin, and riboflavin, however, see only marginal decreases due to the canning medium.

Legumes, recognized for their abundance in B vitamins, iron, copper, magnesium, manganese, zinc, and phosphorous, exhibit a unique nutritional profile compared to other vegetables. They release 10% to 20% of calcium, zinc, phosphorous, sodium, beta-carotene, beta-cryptoxanthin, lycopene, and lutein and zeaxanthin into the canning medium. Iron, magnesium, potassium, riboflavin, and vitamin C experience losses of 25% to 35%, along with significant reductions in copper (45%), B6 (50%), thiamin (60%), and folate (70%).

The world of fruits, diverse as it may be, generally encounters a loss of 10% to 20% in potassium, copper, thiamin, riboflavin, niacin, and vitamin B6. Additionally, a 25% reduction is observed in beta-carotene, beta-cryptoxanthin, lycopene, and lutein and zeaxanthin. Folate and vitamin C, however, undergo a more substantial decrease, plummeting by about 50%.

Temporal Impact on Nutrients

Vitamin C undergoes significant degradation over time, paralleled by the susceptibility of many phytochemicals to the passage of time. Anthocyanin, a potent antioxidant responsible for the vibrant blue, purple, or red hues in berries and various produce, is notably vulnerable to the effects of both time and heat.

The evolution of phytochemicals over time adds a layer of complexity to their behavior. Some degrade post-harvest, while others witness an increase during the storage of processed foods for several months. Although hundreds of phytochemicals have been identified, the study of these compounds remains relatively new in the realm of food nutrition, with ongoing discoveries and research shedding light on this intricate subject.

Certain phytochemicals, such as beta-carotene, beta-cryptoxanthin, lycopene, lutein, zeaxanthin, and other carotenoids, exhibit heightened bioavailability after cooking or processing. Isoflavones showcase a notable resistance to heat, a trait shared with stilbenes found in specific berries, like blueberries. The richness of isoflavones is particularly pronounced in soy and legumes.

Additionally, some phytochemicals demonstrate resilience to heat, such as lignans in nuts and legumes, while certain flavonoids in apples, berries, and cherries actually experience an increase with exposure to heat.

The diverse landscape of phytochemicals introduces subcategories with a mix of heat-resistant and heat-sensitive species. Examples include proanthocyanidins in fruits and some vegetables, along with isothiocyanates in cruciferous vegetables. However, sterols found in certain plant oils prove to be less heat-resistant, often succumbing to oxidation in high temperatures.

Safeguarding Nutrient Integrity in Preserved Foods

The storage temperature of home-canned food emerges as a crucial determinant of nutrient retention. A study monitoring certain nutrients in black currant jam over a 13-month storage period revealed significant variations. At 46 degrees, the jam exhibited superior preservation of vitamin C and anthocyanins compared to jam stored at room temperature. Strikingly, jams stored at 99 degrees showed a complete loss of vitamin C.

Various external factors, namely light, heat, oxygen, and moisture content, play pivotal roles in influencing the longevity of nutrients during storage. While the impact of oxygen on nutrient oxidation is minimal due to its depletion during the canning process, moisture content remains fixed and unalterable. Consequently, the focus shifts to manageable factors: the harvest and storage practices.

Optimal preservation involves harvesting produce at peak ripeness and processing it promptly, followed by storing home-canned foods away from direct light in consistently cool temperatures.

Recognizing that nutrient loss is inevitable over time, especially if food has been stored for days without processing, underscores the importance of timely and effective preservation practices. Despite the inherent decline in nutrients during storage, it’s essential to acknowledge that both processed and fresh fruits and vegetables continue to contribute valuable nutrients to your diet.

The emphasis should remain on safe canning practices to prevent potential health risks, as even a modest loss of vitamin C is a far more preferable outcome than the dangers associated with botulism poisoning.

Suggested resources for preppers:

Harvesting and canning wild greens

The #1 food of Americans during the Great Depression

Survival Foods of the Native Americans

If you see this plant when foraging, don’t touch it!