Composition of oxalates in baked taro (Colocasia esculenta var. Schott) leaves cooked alone or with additions of cows milk or coconut milk

Nutritional, phytochemical composition and potential health benefits of taro (Colocasia esculenta L.) leaves: A review

Colocasia esculenta(L) or taro is a tropical crop largely produced for its tubers (corms) while leaves and stems remain underutilized and untapped by-products with promising potential applications.Colocasialeaves are low in calories, rich in proteins, dietary fiber, and micronutrients. However, its utilization as food remains limited owing to the lack of awareness vis-à-vis its nutritional profile and the presence of antinutrients such as tannins, phytates and oxalates. The antinutritional factors can be overcome by cooking and varied processing techniques thereby unveiling the nutritional benefits. The high content of bioactive compounds and antioxidative potential of colocasia leaves renders several health benefits such as anticancer, antidiabetic, anti-inflammatory activity. The paper reviews the available literature on the nutritional, antinutritional, phytochemical profile of taro leaves and the advanced analytical techniques for their identification and quantification. Further, its health benefits and food applications have been discussed.

Feed utilization and lactational performance of Friesian cows fed beet tops silage treated with lactic acid bacteria as a replacement for corn silage

Thirty multiparous lactating Friesian cows were used to study the effect of partial or complete replacement of corn silage with lactic acid bacteria (LAB), molasses and calcium carbonate ensiled sugar beet tops for 3 months in a complete randomized experimental design with repeated measures. A week after parturition, cows were grouped into three treatments of 10 cows each and fed a control treatment containing corn silage at 300 g/kg DM. In the other treated diets, 50% or 100% of the control corn silage was substituted with beet tops silage treated with LAB included at 150 g or 300 g per kg diet. Ensiling of beet tops with LAB decreased its contents of oxalic acid and neutral detergent and acid detergent fibers but increased its contents of non-structural carbohydrate and calcium. Without affecting daily milk production and feed efficiency, beet tops silage treated with LAB diets decreased (p < 0.05) feed intake, total ruminal volatile fatty acids, acetate and propionate concentrations, energy-corrected milk yield and concentrations of milk total solids, fat, protein and energy. In conclusion, beet tops silage treated with LAB can replace corn silage in diets of lactating cows. An inclusion rate of 15% of beet tops silage treated with LAB (replacing 50% of corn silage) in the diet was the most suitable level for lactating cows under the current experimental conditions.

Potential of Colocasia leaves in human nutrition: Review on nutritional and phytochemical properties

Colocasia esculenta leaves possess vital nutritive and nonnutritive components in significant amounts, but are underutilized, and lesser explored. The chemical composition varies significantly depending upon climatic conditions and other agronomical factors of the location of cultivation and variety. Micronutrients, viz. iron (3.4-11.7 mg 100 g^-1 ), copper (0.29-0.8 mg 100 g^-1 ), magnesium (170-752 mg 100 g^-1 ), potassium (0.4-2.4 g 100 g^-1 ), and zinc (0.6-4.2 mg 100 g^-1 ) are present in high amounts. The ratio of sodium to potassium (1:40) in the leaves add specifically to the antihypertensive properties. Preclinical and clinical studies provide evidence of its antidiabetic, antihemorrhagic, neuropharmacological properties, and as a remedy for stomach and liver ailments. Assessment of phytochemical compounds like chlorogenic acid, anthraquinones, cinnamic acid derivatives, and other phenolics validates these biological properties. The major limiting factor of this plant is oxalate that can be suppressed through food processing strategies. Colocasia leaves are promising green leafy vegetables with nutritional and clinical potential. PRACTICAL APPLICATIONS: Colocasia leaves have demonstrated the ability of antidiabetic, antihypertensive, immunoprotective, neuroprotective, and anticarcinogenic activities. The detailed assessment of phytochemical compounds present in various extracts of the leaves shows the presence of active chemical compounds like anthraquinones, apigenin, catechins, cinnamic acid derivatives, vitexin, and isovitexin which are possibly responsible for the exhibited biological properties. Colocasia leaves are rich sources of micronutrients; however, the presence of oxalates can prohibit proper utilization of these nutrients. Various food processing strategies like soaking, cooking, and so on can significantly reduce the antinutritional content and make these nutrients available for utilization. Documentation of traditional uses and food products from Colocasia leaves show that these leaves have immense potential in the functional food product as well as drug development.

Oxalate Contents of Raw, Boiled, Wok-Fried and Pesto and Juice Made from Fat Hen (Chenopodium album) Leaves

The total, soluble, and insoluble oxalate contents of fresh and wok-fried fat hen (Chenopodium album) leaves were extracted and measured using High pressure liquid chromatography. The total oxalate content of the raw leaves was 1112.4 mg/100 g dry matter (DM), and the levels were significantly reduced by boiling (682.8 mg/100 g DM) or cooking the leaves in a wok (883.6 mg/100 g DM). The percentages of soluble oxalate contents in the total oxalates of the raw and boiled leaves were similar (mean 75%), while the proportion of soluble oxalate content in the wok-fried leaves was reduced to 53.4% of the total, giving a significant increase in the insoluble oxalate content of the wok-fried leaves. The percentage of insoluble calcium in the total calcium was significantly reduced (p < 0.05) when the leaves were boiled, but the insoluble oxalate content significantly increased (67.2%) in the wok-fried leaves when compared to the content of the original raw leaves. Processing the cooked leaves into pesto or extracting the juice gave final products that contained significantly reduced total and soluble oxalate contents. The addition of calcium chloride to the juice caused a very small reduction in the soluble oxalate content in the juice.

Oxalate Content of Taro Leaves Grown in Central Vietnam

Leaves were harvested from four different cultivars of Colocasia esculenta and three cultivars of Alocasia odora that were growing on nine different farms in central Vietnam. The total, soluble and insoluble oxalate contents of the leaves were extracted and measured using HPLC chromatography. Total calcium determinations were also carried out on the same samples. The total oxalate content of the leaves ranged from 433.8 to 856.1 mg/100 g wet matter (WM) while the soluble oxalate ranged from 147.8 to 339.7 mg/100 g WM. The proportion of soluble oxalate ranged from 28% to 41% (overall mean 35%) of the total oxalate content of the leaves. The equivalent insoluble oxalate proportion ranged from 59% to 72% of the total (overall mean 65%). There was little difference between the Colocasia esculenta and Alocasia odora taro cultivars, although the total oxalate content was significantly higher in Alocasia odora cultivars. The overall mean total calcium content was 279.5 mg/100 WM and the percentage of insoluble calcium bound as calcium oxalate ranged from 31.7% to 57.3% of the total calcium content (overall mean 47.1%). The oxalate content in taro leaves is a major factor to consider when different cultivars of taro are recommended for human or animal consumption.

Addition of calcium compounds to reduce soluble oxalate in a high oxalate food system

Spinach (Spinacia oleracea L.) is often used as a base vegetable to make green juices that are promoted as healthy dietary alternatives. Spinach is known to contain significant amounts of oxalates, which are toxic and, if consumed regularly, can lead to the development of kidney stones. This research investigates adding 50-500mg increments of calcium carbonate, calcium chloride, calcium citrate and calcium sulphate to 100g of raw homogenates of spinach to determine whether calcium would combine with the soluble oxalate present in the spinach. Calcium chloride was the most effective additive while calcium carbonate was the least effective. The formation of insoluble oxalate after incubation at 25°C for 30min is a simple practical step that can be incorporated into the juicing process. This would make the juice considerably safer to consume on a regular basis.

Oxalate Content of the Herb Good-King-Henry, Blitum Bonus-Henricus

The total, soluble and insoluble oxalate contents of the leaves, stems and buds of Good-King-Henry (Blitum Bonus-Henricus) were extracted and measured using HPLC chromatography. The large, mature leaves contained 42% more total oxalate than in the small leaves and the soluble oxalate content of the large leaves was 33% higher than the smaller leaves. Cooking the mixed leaves, stems and buds in boiling water for two minutes significantly (p < 0.05) reduced the total oxalate when compared to the raw plant parts. Pesto sauce made from mixed leaves contained 257 mg total oxalate/100 g fresh weight; this was largely made up of insoluble oxalates (85% of the total oxalate content). Soup made from mixed leaves contained lower levels of total oxalates (44.26 ± 0.49 mg total oxalate/100 g fresh weight) and insoluble oxalate made up 49% of the oxalate contents. The levels of oxalates in the Good-King-Henry leaves were high, suggesting that the leaves should be consumed occasionally as a delicacy because of their unique taste rather than as a significant part of the diet. However, the products made from Good-King-Henry leaves indicated that larger amounts could be consumed as the oxalate levels were reduced by dilution and processing.

Oxalate content of silver beet leaves (Beta vulgaris var. cicla) at different stages of maturation and the effect of cooking with different milk sources

The work presented here indicates that people who have a tendency to develop kidney stones should avoid consuming regrowth and developed silver beet (Beta vulgaris var. cicla) leaves. Soluble oxalate contents of leaves range from 58% of the total oxalate for the mature leaves up to 89% for the regrowth tissue, with regrowth tissue containing the highest levels of soluble oxalate at 7267+/-307 mg/100 g of dry matter (DM). Leaves cooked in milk contained significantly (p<0.05) lower levels of soluble oxalate compared to the leaves that were cooked in water. Leaves cooked in low fat milk contained significantly lower levels (p<0.05) of soluble oxalate (1.9%) than leaves cooked in standard milk (5.3%) or cream (6.3%). To maximize the reduction of soluble oxalate during the cooking of high oxalate foods such as spinach and silver beet, a low fat milk cooking medium with neutral pH should be utilized.