Formulation of a dry green tea-apple product : study on antioxidant and color stability

A dry apple product enriched with green tea (GT) extract was designed as a novel food to deliver relevant amounts of catechins. The target water activity (aw) range between 0.11 and 0.32 was chosen for the GT-fortified apple, since it corresponds to low water mobility and, consequently, maximum stability of dehydrated apples. The GT-fortified product and a control dehydrated apple product were stored in air, at 30 \u25e6C, and evaluated for color, antioxidant contents (monomeric flavan 3-ols, total procyanidins, ascorbic acid, chlorogenic acid and dihydrochalcones), ferric reducing/antioxidant power (FRAP), and 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl radical (DPPH) scavenging capacity. After 1 mo of storage at the lowest aw level (0.11), the GT-fortified product retained 80 and 100% of the initial contents of the monomeric flavan 3-ols and total procyanidins, respectively. With increasing aw level to 0.32, the stability of antioxidants slowly decreased. The addition of GT to the apple product increased the FRAP value and the DPPH scavenging capacity by 3.6-fold and 4.6-fold respectively, which remained almost unchanged during storage. The GT-fortified product was similar in color to commercially available dehydrated apples. Results highlighted some advantages of using dehydrated apples as a target for green tea fortification, which deserve further trials to investigate potential applications for fortification of other dehydrated fruits

Rate of antioxidant degradation and color variations in dehydrated apples as related to water activity

Dehydrated apples were studied to evaluate the effects of water activity on the stability of their antioxidants and color. Apples were freeze-dried, ground, then equilibrated, and stored at eight water activity levels, ranging from 0.058 to 0.747, at 40 \ub0C. Their contents of hydroxycinnamic acids, dihydrochalcones, catechin, epicatechin, polymeric flavan-3-ols, and hydroxymethylfurfural, their antioxidant activity values, and their Hunter colorimetric parameters were analyzed at different storage times. Antioxidant degradation followed pseudo-first-order kinetics and was accelerated by increasing the water activity. The order of antioxidant stability in the products at water activity levels below 0.316 was catechin, epicatechin, and ascorbic acid < total procyanidins < dihydrochalcones and p-coumaric acid < chlorogenic acid; however, in the products at water activity levels above 0.316, the degradation of all antioxidants was very fast. The hydroxymethylfurfural formation rate increased exponentially during storage, especially at high water activity levels. The antioxidant activity of the dehydrated apples decreased during storage, consistent with antioxidant loss. The variations of the colorimetric parameters, namely, lightness (L*), redness (a*), and yellowness (b*), followed pseudo-zero-order kinetics and were accelerated by increasing water activity. All analytical indices indicated that the dehydrated apples were stable at water activity levels below 0.316, with the degradation rate accelerating upon exposure to higher relative humidities. Above 0.316, a small increase in water activity of the product would sharply increase the degradation rate constants for both antioxidant and color variations

Modeling Hygroscopicity, Antioxidant Properties and Color Changes of a Dehydrated Green Tea : Apple Product

A fortified apple product was obtained by freeze-drying a heat stabilized apple puree formulated with a green tea water extract. A single serving (50 g) of this product provides 130 mg of epigallocatechin gallate, which is an amount comparable to that found in a cup of tea. The addition of tea extract increased 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity by 4.6-fold with respect to an unfortified apple product that served as control. Quality of dehydrated products is critically dependent upon storage humidity. Hence, the aim of this study was to evaluate the hygroscopicity, antioxidant properties, and color of the fortified and control products at the time of production and during storage in different water activity environments (aw = 0.109 - 0.736) in the dark at 30\ub0C. The adsorption isotherm of the product fitted the Guggenheim-Anderson-de-Boer equation and was not affected by tea addition. Estimated monolayer water content was 0.106 g water/g dry solids(confidence limits at 95%: 0.093 and 0.120). During storage the colorimetric parameters L* (lightness) and b* (yellowness) decreased, whereas a* (redness) increased. The pseudo-zero order rate constants for changes in color were minimal at the monolayer water activity and increased with increasing water activity. The degradation of flavanols, dihydrochalcones, chlorogenic acid and ascorbic acid followed pseudo-first order kinetics, with the slowest rates at the lowest water activity. Ascorbic acid was the most unstable; the pseudo-first order rate constants for its degradation changed from 0.0049 +/- 0.0007 to 0.54 +/- 0.04 days-1 with increasing water activity from 0.109 to 0.736. Kinetic equations were used to devise mathematical models to predict quality changes of the fortified product during storage as a function of water activity. A water activity range of 0.109-0.327 was found to be optimal to maintain the antioxidant properties and color of the product

Effect of storage on phytochemical stability, color, antioxidant activity, and inhibition of formation of fructose-induced advanced glycation endproducts of an intermediate moisture apple-green tea product

Oral presentation #1242785 selected for ACS/AGFD Withycombe-Charalambous Graduate Student Symposium. This study evaluated the effects of storage (aw 0.736, 30\ub0C) on attributes of intermediate moisture products made with apple (control) or apple and green tea extract. Products were evaluated for soluble solids, pH, titratable acidity, color (L*,a*,b*), flavanol and ascorbic acid contents, total polyphenols, ferric reducing antioxidant potential (FRAP), 2,2-diphenyl- 1-(2,4,6-trinitrophenyl)hydrazyl radical (DPPH) scavenging activity, and ability to inhibit formation of fructose-induced advanced glycation endproducts (AGE). A single serving of the fortified product (50 g) provided equivalent catechin content to one cup of green tea. Total phenolics, FRAP values, DPPH radical scavenging activity and inhibition efficiency of fructose-induced AGE formation were about 3-5 times greater for the fortified product than control. Over storage for 45 days, antioxidant contents decreased moderately. However, the fortified product maintained much higher antioxidant and anti-AGE formation activities than the control, suggesting that it could have potential benefits for metabolic syndrome or diabetic consumers

Stability and anti-glycation properties of intermediate moisture apple products fortified with green tea

Intermediate moisture products made from blanched apple flesh and green tea extract (about 6 mg of monomeric flavan 3-ols added per g of dry apple) or blanched apple flesh (control) were produced,and their quality attributes were investigated over storage for two months at water activity (aw) levels of 0.55 and 0.75, at 30 \ub0C. Products were evaluated for colour (L*, a*, and b* Hunter\u2019s parameters), phytochemical contents (flavan 3-ols, chlorogenic acid, dihydrochalcones, ascorbic acid and total polyphenols), ferric reducing antioxidant potential, 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl radical-scavenging activity and ability to inhibit formation of fructose-induced advanced glycation end-products. During storage of the fortified and unfortified intermediate moisture apples, water availability was sufficient to support various chemical reactions involving phytochemicals, which degraded at different rates: ascorbic acid > flavan 3-ols > dihydrochalcones and chlorogenic acid. Colour variations occurred at slightly slower rates after green tea addition. In the intermediate moisture apple, antioxidant and anti-glycoxidative properties decreased at similar rates (half-life was about 80 d at aw of 0.75, 30 \ub0C). In the green tea-fortified intermediate moisture apple, the antioxidant activity decreased at a slow rate(half-life was 165 d at aw of 0.75, 30 \ub0C) and the anti-glycoxidative properties did not change, indicating that flavan 3-ol degradation involved the formation of derivatives that retained the properties of their parent compounds. Since these properties are linked to oxidative- and advanced glycation end-product-related diseases, these results suggest that green tea fortification of intermediate moisture apple products could be a valuable means of product innovation, to address consumers\u2019 nutritional needs

Detecting correlation between extreme probability events

As classical definitions of correlation give rise to counterintuitive statements when extreme probability events are involved, we introduce enhanced notions of positive and negative correlation in the general framework of coherent conditional probability. These notions allow to handle extreme probability events in a principled way by accommodating the different levels of strength of the zero probabilities involved (namely, zero layers). Since the detection of correlations by means of zero layers is computationally challenging, we provide a full characterization relying on only conditional probability values

Il fascino della matematica e delle sue applicazioni

Il fascino della matematica e delle sue applicazioni e` un progetto del Dipartimento di Scienze di Base e Applicate per l'Ingegneria finanziato nell'ambito de bando terza missione per l'anno 2020 di Sapienza Universita` di Roma. L'iniziativa ha avuto come scopo quello di diffondere non solo gli aspetti piu` intriganti della matematica, ma anche le sue ricadute sulle scienze applicate, attraverso una serie di seminari, tenuti da docenti universitari e docenti di scuola superiore, rivolti principalmente a un pubblico di studenti della scuola superiore. Il testo raccoglie il contributo di alcuni degli oratori coinvoti nei seminari