Variation in Antioxidant Activity, Total Phenolics, and Nitrate in Spinach

Vegetable Soups and Creams: Raw Materials, Processing, Health Benefits, and Innovation Trends

Vegetable soups and creams have gained popularity among consumers worldwide due to the wide variety of raw materials (vegetable fruits, tubers, bulbs, leafy vegetables, and legumes) that can be used in their formulation which has been recognized as a healthy source of nutrients (mainly proteins, dietary fiber, other carbohydrates, vitamins, and minerals) and bioactive compounds that could help maintain the body’s health and wellbeing. In addition, they are cheap and easy to preserve and prepare at home, ready to eat, so in consequence they are very useful in the modern life rhythms that modify the habits of current consumption and that reclaim foods elaborated with natural ingredients, ecologic, vegans, less invasive production processes, agroindustry coproducts valorization, and exploring new flavors and textures. This review focuses on the nutritional and healthy properties of vegetable soups and creams (depending on the raw materials used in their production) highlighting their content in bioactive compounds and their antioxidant properties. Apart from the effect that some processing steps could have on these compounds, innovation trends for the development of healthier soups and creams adapted to specific consumer requirements have also been explored.

Industrial freezing effects on the content and bioaccessibility of spinach (Spinacia oleracea L.) polyphenols

BACKGROUND

Spinach is well recognized as a functional food owing to its diverse nutritional composition, including polyphenols. Freezing is an efficient preservation method that is used to maintain the physical and nutritional characteristics and extend the shelf life of spinach. The aim of this study was to determine the changes in polyphenols in the samples taken from various production steps of the industrial freezing process of spinach, and to evaluate the bioaccessibility of these bioactive compounds for raw material, by-product, and frozen product using the standardized in vitro digestion model simulating the digestion in the mouth, stomach, and intestine.

RESULTS

Ultra-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry and high-performance liquid chromatography equipped with photodiode array detection analysis of spinach samples led to the identification of eight flavonoids and two phenolic acids. The changes occurring in flavonoids after blanching, chopping, and freezing steps were statistically not significant compared with the raw material (P > 0.05). On the other hand, by-product was found to contain significantly lower amounts of flavonoids (98% in total) and phenolic acids (90% in total) (P < 0.05) compared with the raw material. Furthermore, after in vitro digestion, frozen spinach was found to contain higher amounts of bioaccessible flavonoids (15% in total) and phenolic acids (16% in total) compared with fresh spinach.

CONCLUSION

Overall, the current study highlighted that industrial freezing might be a good strategy to preserve the polyphenol content of fresh spinach as well as to enhance the total amount of bioaccessible polyphenols.

Plant growth, phytochemical accumulation and antioxidant activity of substrate-grown spinach

Spinach production in soilless cultivation systems, mainly in substrate, transplanted with soil blocks and drip-irrigation is increasing worldwide. However, spinach establishment with soil blocks, with several seedlings per block compared with traditional planting methods, may affect light interception by plant canopy, wetting and salt patterns in root medium and therefore the plant growth and functional value of spinach. The effects of soil block number (plant density) and emitters spacing on plant growth, nitrate, proline and total phenols content and antioxidant activity were evaluated in spinach (Spinacia oleracea L). Five seedlings per soil block were transplanted to Styrofoam boxes filled with the substrate and grown during winter in an unheated greenhouse. Four treatments were carried out with two soil block numbers [8 (160 plants/m²) and 14 (280 plants/m²) soil blocks per Styrofoam box] and two emitter spacing [emitters spaced every 25 and 12.5 cm, respectively, with 4 and 8 emitters per Styrofoam box]. Neither plant density nor emitter spacing had any effect on shoot dry weight. Fresh yield increased as planting density and the number of emitters per Styrofoam box increased. The yield in Styrofoam boxes with 160 plants/m² and 8 emitters (3.85 kg m⁻²) was ≈31 % lower than that obtained in treatment with 280 plants/m² and 8 emitters (5.09 kg m⁻²). However, the leaf blade of the latter treatment presented a higher content of phenols and proline and greater antioxidant activity (FRAP and DPPH) as well as lower content of nitrate and lesser PDH activity. Decrease of space between emitters reduced the leaf blade nitrate concentration of spinach grown in a greenhouse during the winter. Leaf blade antioxidant activity (FRAP) decreased as planting density increased.

Varietal dependence of chemoprotective substances in fresh and frozen spinach (Spinacia oleracea, L.)

Spinach (Spinacia oleracea L.) is an important source of bioactive compounds. It is commonly consumed fresh or frozen products. Spinach is rich sources of polyphenols, it is a good source of vitamin C and has potential beneficial properties for human health. This study provides some knowledge about content of total polyphenols, and antioxidant activity in selected varieties of fresh and frozen spinach samples. Four spinach cultivars (̓Boa ̓, ̓ Hudson ̓, ̓Chica ̓, ̓Trombone ̓) were analysed. The content of the total polyphenols (TPC) was determined by the Folin-Ciocalteu reagent (FCR). Antioxidant activity (AA) was measured using a compound DPPH (2,2-diphenyl-1-picrylhydrazyl). The content of total polyhenols in fresh samples of spinach ranged from 975 ±97.15 mg.kg-1 to 1493 ±50.42 mg.kg-1 and values of antioxidant activity were in interval from 77.55 ±0.34% to 82.57 ±0.83%. The highest level of TP content in fresh spinach was recorded in variety Hudson (1493 mg.kg-1) and the lowest in variety Chica (975 mg.kg-1). Between these varieties statistically significant difference in the content of total polyphenols was found. The highest value of antioxidant activity in fresh spinach was recorded in variety Trombone (82.57%) and the lowest in variety Boa (78.59%). This difference was also statistically significant. The highest level of TP content in frozen spinach samples was found in variety Hudson (1749 mg.kg-1) and the lowest in variety Chica (855 mg.kg-1). The values of antioxidant activity in frozen spinach samples were in range from 45.86 ±7.84%to 79.67 ±0.88%. The highest value of antioxidant activity in frozen spinach was found in variety Hudson (79.67%) and the lowest in variety Chica (45.86%).