Effect of vacuum cooking treatment on physicochemical and structural characteristics of purple-flesh potato

The Influence of the Addition of Fruit and Vegetable Concentrates on the Stability of Anthocyanins in Juices from Colored Potatoes

One of the factors precluding potato juice application in the food industry is its propensity for enzymatic browning. The addition of fruit and vegetable concentrates rich in organic acids can reduce unfavorable changes in the color of potato juices and influence the content of biologically active compounds. This study aimed to investigate the effect of the addition of natural fruit and vegetable concentrates to potato juices on their color and on the composition and contents of anthocyanin pigments isolated from them. The color, composition and amount of anthocyanins in potato juices and dyes were determined using HPLC-DAD and UHPLC MS/MS liquid chromatography. It was found that the juices without concentrate addition had, on average, 61% lower total polyphenol content and 63% lower anthocyanin content compared with the juices with added concentrates. The isolated pigments contained, on average, 30-40 times more anthocyanins compared with those isolated from the non-purified juices. Furthermore, the addition of concentrates enabled ca. 3-5 times more effective isolation of anthocyanins compared with the samples without these additives. Potato juices and dyes with the addition of concentrates showed a lighter color that did not change over time, compared with samples without concentrates.

Stability of color and biologically active compounds of pasteurized juices from potatoes with colored flesh

Juices from potato varieties with colored flesh contain a large amount of biologically active compounds, but they tend to darken enzymatically, which deteriorates the quality. One of the factors that can improve the color of juices is pasteurization. The aim of the study was to investigate the effect of pasteurization temperature on the anthocyanin content and color of juices from potatoes with colored flesh. The research material included juices from potato varieties with red and purple flesh. Juices pasteurized at 75 °C were characterized by the lightest color and an increase in the a* (red color) and b* (yellow color) parameters compared to unpasteurized juices. Pasteurization of juices reduced the amount of glycoalkaloids by an average of 54% compared to unpasteurized juices (larger losses in the content of α-chaconine than α-solanine). Purple potato juices showed a higher content of total polyphenols by an average of 30% and anthocyanins by 70% than juices from red potatoes. Pelargonidin and its derivatives were identified in red potato juices, while petunidin and peonidin were the most abundant in purple potato juices. Higher losses of total polyphenols were found in juices from red varieties of potatoes, while anthocyanins were less thermostable in juices from varieties with purple flesh.

Comparative elucidation on the phenolic fingerprint, sugars and antioxidant activity of white, orange and purple-fleshed sweet potatoes (Ipomoea batatas L.) as affected by different cooking methods

In this study, three cooking methods (baking, boiling, sous vide (SV)) were applied to Turkish sweet potatoes with three flesh colors (white, orange, purple) to examine the effects of the product color and cooking methods on the total phenolics, antioxidant activity, sugars, phenolic acids, and anthocyanins. LC-MS-MS was employed in the characterization of these compounds. It was observed that the product color and cooking method significantly affected the concentrations of bioactive compounds like polyphenols. Both the highest total phenolic content (11.36 mg/g) and antioxidant activity (DPPH (50.3 μM TE/g) and ABTS (63.53 μM TE/g)) were determined in the purple sweet potato cooked with the SV method. 10 phenolic acids were quantified in all samples which were in the highest amounts in the orange colored samples followed by the purple samples. Baking resulted in the highest total phenolic acids in all samples. 13 anthocyanins were detected in the purple-colored samples, while the SV cooking best preserved the anthocyanins. In sum, purple sweet potatoes cooked by SV are recommended for higher phenolic contents, antioxidant capacity and anthocyanins.

Effect of Cooking Methods on Bioactivity of Polyphenols in Purple Potatoes

Purple-fleshed potato (Solanum tuberosum L.) is a good dietary source of anthocyanins, flavonols, and polyphenolic acids, mostly chlorogenic acid. The objective of this study was to examine the impacts of cooking methods including boiling, steaming, and the newly developed vacuum-sealed boiling (VSBoil) on extractability and bioactivity of polyphenolic compounds in a purple potato (PP) cultivar, Purple Pelisse. Data showed that boiling and steaming reduced the total polyphenolic content in PP. High-performance liquid chromatography analysis showed that steaming slightly reduced the extractable chlorogenic acid content, while VSBoil increased it. For DPPH free radical scavenging activities, VSBoil and steaming effectively preserved the antioxidant activity of a polyphenol-rich extract of PP, while boiling resulted in a significant reduction compared to raw potato extract. All extracts effectively suppressed bursts of intracellular reactive oxygen species in human colonic epithelial cells upon hydrogen peroxide induction, of which the extract from the VSBoil group showed the highest antioxidant potential. In addition, all extracts showed anti-inflammatory effects in Caco-2 cells induced with tumor necrosis factor-α. In conclusion, the content and bioactivity of extractable polyphenols were largely retained in PP subjected to different cooking processes. VSBoil resulted in the highest content of extractable polyphenolic compounds and bioactivity among tested cooking methods.

Comparison of physical, microstructural and antioxidative properties of pumpkin cubes cooked by conventional, vacuum cooking and sous vide methods

BACKGROUND

Current dietary guidelines recommend five or more fruit, vegetable, and legume servings per day. Often, these products are eaten cooked, resulting in organoleptic and nutritional changes. Vacuum cooking is gaining attention as an alternative cooking technique, due to its ability to preserve or even enhance sensory and healthy properties of food. Its household application is, however, poorly explored. In this work, the effect of vacuum cooking, performed with a new patented system, was studied for the first time on pumpkin cubes and compared to sous vide and traditional steam cooking, through a multidisciplinary approach.

RESULTS

All the cooking treatments damaged pumpkin microstructure, leading to cell separation and plasmolysis; vacuum cooking was the most aggressive method, as confirmed by texture softening. Vacuum cooking was also the method with less impact on pumpkin color, in relation to the largest extraction of some classes of carotenoids from the broken cells. Significant polyphenol extraction, especially of gallic acid and naringenin, was instead observed for sous vide and steamed pumpkins. The total antioxidant activity, ascribable to the effect of both carotenoids and polyphenols, resulted enhanced after cooking compared to raw one mainly for cook vide samples, followed by steamed and sous vide ones.

CONCLUSIONS

Vacuum cooking, followed by sous vide, has often shown better performance than traditional steam cooking for pumpkin cubes. The implementation of sous vide and vacuum cooking at domestic level or in professional kitchens, and in the food industry, would allow the consumption of vegetables with improved nutritional and sensorial characteristics. © 2020 Society of Chemical Industry.

Effect of different atmospheric and subatmospheric cooking techniques on qualitative properties and microstructure of artichoke heads

Quartered Violetto artichokes were cooked with different treatments (boiling, steaming, sous vide and vacuum cooking) at the same cooking value at the thermal centre. Then, the physical (moisture content, texture and colour), histological and chemical (phenolic, 5-hydroxymethylfurfural (HMF) and furan content, total antioxidant capacity) features of bracts and hearts were assessed. A deeply modified microstructure was observed in boiled and steamed samples with an evident decrease in hardness both for bracts and hearts. Lightness of two anatomical parts was decreased by all the treatments (with the exception of sous vide bracts). The highest total colour difference was recorded for steamed samples, whereas the lowest was noted for sous vide samples. Steamed and sous vide artichoke exhibited the highest total phenolic content and total antioxidant capacity. Sous vide samples exhibited the highest concentrations of HMF, 2-furan-methanol and 2,4-dihydroxy-2,5-dimetyl-3(2H)-furanone, whereas the by-product 5-metylfuraldheide was only detected in the steamed product.

Evaluating and correlating the mechanical, nutritional, and structural properties of carrots after multiple freezing/thawing processing

This work evaluated and correlated the mechanical and nutritional properties of carrots after five freezing/thawing cycles (FTC). Results showed that after one FTC, the mechanical parameters (hardness, chewiness, springiness, cohesiveness, resilience, and storage modulus) and the glucose and fructose content sharply decreased and the tangent (Tanδ) dramatically increased in samples. The contents of lycopene and lutein reached the maximum level after two FTC. And there were no significant changes in the content of α- and β-carotene (around 90 and 50 mg 100 g-1 dry matter, respectively) among all samples. Correlation analysis showed that the mechanical parameters were positively correlated with soluble sugars (fructose, glucose, and sucrose) and negatively with lycopene and lutein Tanδ were negatively related with soluble sugar. These results suggested that the first freezing/thawing condition could be the key factor for obtaining the products with acceptable quality. The changes in macroscopic mechanics could be used to predict the variations of potential nutritional components in tissues during FTC processing. The deteriorated structural changes (i.g. cell wall dissociation and turgidity loss) could be responsible for these results.