Issis Quispe-Fuentes

Assessment of vacuum-dried peppermint (Mentha piperita L.) as a source of natural antioxidants

The purpose of this study was to investigate the effect of temperature in the vacuum drying process of Mentha piperita L. (50 to 90 °C). Generally, drying processes affect the quality of product, however, vacuum drying works under sub-atmospheric pressures. In order to investigate how temperature affects this herb, as to color, chlorophyll, total phenolic (TPC), total flavonoid (TFC) contents, antioxidant activity by DPPH and ORAC methods. Mineral, vitamin C and sugar contents were also evaluated. A slight change in color and chlorophyll content was observed in the samples. The highest values for TPC, TFC and antioxidant activity methods were obtained at 50 and 70 °C however, a decrease in the vitamin C content was observed. Minerals such as K, Ca, Mg and Na were found. Sucrose showed the highest sugar content. This work suggests that M. piperita L. can be used as a natural antioxidant, whether fresh or dried.

Influence of drying temperature on dietary fibre, rehydration properties, texture and microstructure of Cape gooseberry (Physalis peruviana L.)

The effects of air drying temperature on dietary fibre, texture and microstructure of the Cape gooseberry fruits during convective dehydration in the range of 50–90 ºC were investigated. The ratio of insoluble dietary fibre to soluble dietary fibre was higher than 7:1 for all dehydrated samples. At 50 ºC tissue structure damage was evidenced leading to the maximum water holding capacity (47.4 ± 2.8 g retained water/100 g water) and the lowest rehydration ratio (1.15 ± 0.06 g absorbed water/g d.m.). Texture analysis showed effects of drying temperatures on TPA parameters. Changes in microstructure tissue were also observed at the studied drying temperatures. Hot air drying technology leads not only to fruit preservation but also increases and adds value to Cape gooseberry, an asset to develop new functional products.

Extraction Techniques for Bioactive Compounds and Antioxidant Capacity Determination of Chilean Papaya (Vasconcellea pubescens) Fruit

The aim of this work was to assess and compare different extraction methods by using high hydrostatic pressure (HHPE), ultrasound (UE), agitation (AE), and their combinations for the extraction of bioactive compounds of Chilean papaya. Extract antioxidant capacity was evaluated by three methods (i.e., DPPH, FRAP, and Voltammetry) and phenolic compounds and vitamin C were determined by HPLC. Papaya sample extraction was performed by HHPE at 500 MPa for 10 min and UE and AE for 30 min, respectively. The combined-extractions: HHPE-UE and HHPE-AE, were carried out for 5 min and 15 min, respectively. The highest values found were total phenolic 129.1 mg GAE/100 g FW, antioxidant capacity by DPPH 20.6 mM TE/100 g FW, and voltammetry 141.0 mM TE/100 g FW for HHPE-UE method in free compound extraction. Regarding vitamin C content, its highest value was found by HHPE-UE (74 mg/100 g FW) a combined extraction method. The phenolic compounds rutin and p-coumaric acid were found in all the extracts, both in free and bound forms, respectively. Besides, the combined techniques improved the extraction of bioactive compounds.

Antioxidant Compound Extraction from Maqui (Aristotelia chilensis [Mol] Stuntz) Berries: Optimization by Response Surface Methodology

The optimum conditions for the antioxidant extraction from maqui berry were determined using a response surface methodology. A three level D-optimal design was used to investigate the effects of three independent variables namely, solvent type (methanol, acetone and ethanol), solvent concentration and extraction time over total antioxidant capacity by using the oxygen radical absorbance capacity (ORAC) method. The D-optimal design considered 42 experiments including 10 central point replicates. A second-order polynomial model showed that more than 89% of the variation is explained with a satisfactory prediction (78%). ORAC values are higher when acetone was used as a solvent at lower concentrations, and the extraction time range studied showed no significant influence on ORAC values. The optimal conditions for antioxidant extraction obtained were 29% of acetone for 159 min under agitation. From the results obtained it can be concluded that the given predictive model describes an antioxidant extraction process from maqui berry.

Evaluation of phenolic profiles and antioxidant capacity of maqui (Aristotelia chilensis) berries and their relationships to drying methods: Evaluation of phenolic profiles and antioxidant capacity of maqui

BACKGROUND Five drying methods (freeze, convective, sun, infrared, and vacuum drying) were applied to maqui berries to establish their effect on phenolic compounds and antioxidant capacity. Total phenolic, total flavonoid, and total anthocyanin contents were measured by spectrophotometry, anthocyanin and phenolic profiles were analyzed by chromatography, and the antioxidant capacity was determined. This study is probably the first to demonstrate the variation and stability of bioactive compounds from maqui berries after applying different drying methods. RESULTS The highest content of phenolic and antioxidant compounds was obtained by using the freeze-drying method compared with fresh samples (P < 0.05). Eight anthocyanins were identified in all dehydrated maqui samples. Compared with fresh maqui, freeze-dried samples retained 73% and 64% of delphinidin and cyanidin derivatives respectively. Sun- and vacuum-dried samples conserved some phenolic acids. Vacuum-dried maqui retained a higher amount of free flavonols. CONCLUSION This study demonstrated that the application of any drying method results in a final product with good levels of phenolic compounds.