Potassium/Calcium ratio affects quality and colour of Selva strawberries
High-quality fruit production is the cornerstone of marketability. The optimum performance of soil-less plants depends on the well-balanced and prompt availability of minerals in nutrient solutions. In addition to concentration, nutrient ratio also plays an essential role in growth, productivity, quality and nutrient absorption.
Researchers from the Islamic Azad University (Mahabad, Iran) studied the effects of different Potassium:Calcium ratios (K:Ca; 1.6, 1.4, 1.2, 1, 0.85 and 0.6) in nutrient solutions on the quality of remontant Selva strawberries grown using soil-less techniques.
The highest and lowest leaf number and leaf areas were observed for K:Ca ratios 1.4 and 1 respectively. The highest values of fruit pH, conductivity, total soluble solid/titratable acidity ratio, vitamin C content, ellagic acid and colour were observed for K:Ca ratio 1.4. K:Ca ratio 1.6 produced strawberries with a higher protein content, while K:Ca ratio 0.85 was more effective on fruit firmness.
Source: Haghshenas Masoud, Arshad Mousa, Nazarideljou Mohammad Javad, 'Different K:Ca ratios affected fruit color and quality of strawberry 'Selva' in soilless system', 2018, Journal of Plant Nutrition, Vol. 41 (2), pag. 243-252.
Putting potassium to work reducing sodium
Dec. 26, 2017 - by Jeff Gelski
KANSAS CITY — Potassium chloride remains a popular ingredient in order to reduce sodium and add potassium in food products, but that’s not the only way potassium may be used in sodium reduction strategies. Tripotassium citrate (potassium citrate) is one example as it is an option for several applications, including beverages.
Foods rich in potassium are important in managing high blood pressure because potassium lessens the effects of sodium, according to the American Heart Association, Dallas. The more potassium a person eats, the more sodium is lost through urine. Potassium also helps to ease tension in blood vessel walls, which helps further lower blood pressure.
Potassium citrate has a mild, pleasant and salty taste with a potassium content of 36%, said Caitlin Jamison, market development manager of health and nutrition for Jungbunzlauer, Inc. and based in Newton Centre, Mass. Additionally, it is water-soluble.
“This makes it easy to use for beverages,” she said. “Beyond fortification, citrates play a functional role to improve emulsification and reduce heat-related fouling deposits in protein-based beverages.”
The dairy industry and the dairy alternative industry have used sodium citrate for this purpose.
“However, potassium citrate offers similar functionality with the added benefit of providing trace amounts of potassium and a cleaner label,” Ms. Jamison said.
Potassium chloride remains in demand, too. Minneapolis-based Cargill this year opened a new potassium chloride production facility in Watkins Glen, N.Y., that has become the company’s primary production facility for potassium chloride, said Mike Beaverson, senior marketing manager for Cargill Salt.
Potassium chloride has been shown to reduce sodium by up to 50% in a range of applications, including baked foods, soup, ready-to-eat meals, snacks and sauces, according to Cargill. The company offers a variety of potassium chloride products.
“Matching the correct sodium reduction solution will vary depending on the food application,” said Janice Johnson, Ph.D., research development manager for Cargill Salt. “For brine solutions or beverages, Potassium Pro is ideal. FlakeSelect products have a unique shape that promotes faster dissolution, which can be beneficial for protein extraction in meat applications. The FlakeSelect process combines salt and potassium chloride to help prevent segregation, which may have taste benefits in some food applications such as bakery and snacks.”
An NHANES report has shown that 98% of the U.S. population does not consume enough potassium, said Alice Wilkinson, vice-president of nutritional innovation for Watson, Inc., West Haven, Conn.
“Potassium is difficult to formulate with as it has a flavor issue, and the dose is so large that even if it were flavor-neutral, it simply takes up more space than most formulas have,” she said.
Watson has developed a line of encapsulated potassium sources that help reduce flavor concerns.
“We work with potassium phosphates and chlorides in either hot melt lipid encapsulation (or) cellulose encapsulation,” Ms. Wilkinson said. “Some are designed as thin layer to keep use rates down, and our customers are having success with these products in a variety of food types, including bars and beverages.”
Potassium bicarbonates may be used as direct replacements for sodium bicarbonates in leavening applications. Church & Dwight, Inc., Ewing, N.J., offers Flow-K potassium bicarbonate, a food grade potassium bicarbonate product composed of a proprietary flow aid system that assures excellent storage and handling properties, according to the company. It allows for reduced sodium levels while maintaining overall quality and flavor. This product commonly is used in the leavening system for cakes, muffins, and cookies. It also may be used in effervescent drink mixes.
Jungbunzlauer’s sub4salt line of products uses blends of salt with potassium-based salts to provide 35% to 50% sodium reduction when used as a 1:1 replacement for salt, Ms. Jamison said. The products include combinations of potassium chloride, potassium gluconate and potassium citrate.
Potassium chloride has been linked to a bitter and metallic taste that may require flavor adjustments in formulations.
“Potassium chloride does have this typical profile, but other salts, including potassium citrate, potassium gluconate and potassium lactate, have a very clean, pleasant taste at intended use levels,” Ms. Jamison said. “In addition, Jungbunzlauer has also found that they can actually help with masking the off-taste in many food products. Some of these may be a bit surprising. For example, potassium citrate may be a logical replacement for sodium citrate when buffering a beverage. However, for certain fruity flavor profiles, such as berries, lactates work very well for enhancing the flavor character.
“Potassium-based salts can also be helpful for masking the linger and off-notes associated with high-intensity sweeteners in low-calorie beverages. Jungbunzlauer has also done work with using potassium citrate as part of a masking system for infant formulas made with protein hydrolysates.”
Potassium concentration and yields in flowering plants
From the different nutrients that are needed by plants we have known for more than 4 decades that potassium is of critical importance to flowering/fruiting plants. Potassium is one of the most highly limited nutrients in soil due to its high mobility and great increases in yields have been achieved with both potassium fertilization in soil and the use of properly balanced nutrient solutions containing enough potassium in hydroponics. But how important is potassium and what is its ideal concentration in hydroponic nutrient solutions when growing flowering plants? Today we are going to take a look at the scientific literature about potassium and what the optimum levels of potassium for different flowering plants might be in order to maximize yields.
There are many studies in the scientific literature dealing with the effect of potassium on various flowering plants. Earlier evidence from the 1980s pointed to optimum concentrations of potassium being close to the 160-200 ppm range. The book "mineral nutrition" by P.Adams (here) summarizes a lot of the knowledge that was available at the time and shows that for the growing techniques available at the time using greater concentrations of K was probably not going to give a lot of additional benefit.
However newer evidence from experiments carried out within the past 10 years shows that optimum potassium concentration might depend on a significant variety of factors, from which media, other nutrient concentrations and growing system type might play critical roles. For example study on strawberries in 2012 (here) showed optimum concentrations of K to be around 300 ppm for strawberries and the optimum media to be a mixture of peat+sand+perlite (image from this article included above).
Evidence from experiments on tomatoes (link here and image from this article above) also shows that for tomatoes the actual optimum concentration of K might actually be larger under some condition with the optimum in this study in terms of fruit quality and yields being 300 ppm. In this last case the tomatoes were grown using a nutrient film technique (NFT) setup. However there have also been studies under other growing conditions - like this one on reused pumice - which shows that increasing K concentrations to 300ppm can actually have detrimental consequences. In this case tomatoes fed at 200, 290 and 340ppm of K had very similar results when using new substrate but the old substrate heavily underperformed when high K concentrations were used.
Papers published on the effect of different K concentrations in melons (here) and cucumbers (here) also point to optimal concentrations in the 200-300 ppm range and for the optimum N:K ratio to be between 1:2 and 1:3 for these plants. This is probably the reason why you will often find suggested nutritional guidelines for flowering plants - like those below taken from here - mostly suggesting K concentrations in the 250-350ppm range. However you will often find that they directly contradict research papers, like this guideline suggesting K of 150 ppm for strawberries while we saw in a recent paper that 300ppm might be better. This is most probably due to differences in the sources used which might have used different growing systems or plant varieties which responded to other conditions better.
All in all the subject of K concentration in hydroponics is no simple one. Using low K will limit your yields tremendously but increasing your K very high can also harm your plants, especially depending on the type of media you are using. In general aiming for a K concentration between 200-250 ppm is safest but in many cases increases to the 300-400ppm range can bring significant increases in plant yields. A careful study of the available literature and the actual growing conditions that the plants will be subjected to will be key in determining what the best K concentration to use will be. Alternatively carrying out adequately designed experiments under your precise growing environment will help you carry out an evidence-based decision about what K concentration to use.
Potassium may help to prevent heart disease
Spinach, carrots, oranges, and bananas are just some fruits and vegetables that are rich in potassium. According to a new study, we may want to consider increasing our intake of such foods; they could help to protect us against heart disease.
Researchers have found that mice with low dietary potassium are more likely to experience vascular calcification, which is characteristic of atherosclerosis. This is major risk factor for heart disease.
Increasing dietary potassium, however, was found to reduce vascular calcification in the rodents, suggesting that a diet rich in potassium could help to prevent heart disease.
The research team - led by Yabing Chen, Ph.D., a professor of pathology at the University of Alabama at Birmingham (UAB) - recently reported their findings in JCI Insight.
Heart disease is the leading cause of death for both men and women in the United States, killing around 610,000 people in the country every year.
Atherosclerosis is a key risk factor for heart disease. In atherosclerosis, deposits of fat, cholesterol, calcium, and other substances accumulate in the arteries, forming what is referred to as "plaque." Plaque hardens over time, restricting blood flow to the heart.
The new research from Prof. Chen and colleagues suggests that potassium supplementation could be one way to help combat atherosclerosis and reduce the risk of heart disease.
Effect of Potassium and Calcium Ions on Heart Function
In the discussion of membrane potentials in Chapter 5, it was pointed out that potassium ions have a marked effect on membrane potentials, and in Chapter 6 it was noted that calcium ions play an especially important role in activating the muscle contractile process. Therefore, it is to be expected that the concentration of each of these two ions in the extracellular fluids should also have important effects on cardiac pumping.
Effect of Potassium Ions. Excess potassium in the extracellular fluids causes the heart to become dilated and flaccid and also slows the heart rate. Large quantities also can block conduction of the cardiac impulse from the atria to the ventricles through the A-V bundle. Elevation of potassium concentration to only 8 to 12 mEq/L—two to three times the normal value—can cause such weakness of the heart and abnormal rhythm that this can cause death.
These effects result partially from the fact that a high potassium concentration in the extracellular fluids decreases the resting membrane potential in the cardiac muscle fibers, as explained in Chapter 5. As the membrane potential decreases, the intensity of the action potential also decreases, which makes contraction of the heart progressively weaker.
Effect of Calcium Ions. An excess of calcium ions causes effects almost exactly opposite to those of potassium ions, causing the heart to go toward spastic contraction. This is caused by a direct effect of calcium ions to initiate the cardiac contractile process, as explained earlier in the chapter.
Conversely, deficiency of calcium ions causes cardiac flaccidity, similar to the effect of high potassium. Fortunately, however, calcium ion levels in the blood normally are regulated within a very narrow range. Therefore, cardiac effects of abnormal calcium concentrations are seldom of clinical concern.