Vacuum Concentration Improves the Quality and Antioxidant Capacity of Pear Paste

Abstract

A vacuum concentration method was established to produce pear paste using fresh pear juice in this study. The optimal condition was determined by comparing the quality indexes, contents of total phenol and flavonoid, and antioxidant properties of the pear paste produced by traditional heating concentration and vacuum concentration. Electronic nose and electronic tongue were introduced in this study to provide digital smell and taste indicators. The results showed that the best vacuum concentration temperature was 65°C, which led to the best sensory evaluation score and pear paste quality. The browning degree and soluble quinones were the lowest in all tested temperatures, and the content were 60.12% and 72.88% compared with the heating method, respectively. While the values were 148.29%, 209.44%, 310.86%, 120.37%, 106.24%, and 181.26% of total phenol, total flavonoid, vitamin C, 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH) and hydroxyl (·OH) radical scavenging rates, and total reducing power, respectively. The electronic nose could effectively distinguish the vacuum-concentrated pear paste from the traditional heating-concentration pear paste and could provide quality guidance on their flavor differences through characteristic sensors. The electronic tongue tests showed that the vacuum-concentrated pear paste had larger freshness and richness kurtosis. The pear paste made by the optimized vacuum concentration method had higher retention of nutritional and functional components and higher antioxidant capacity, which could be clearly differentiated from the traditional process, thus this method had an applicable potential.

Saturated brine dissolution and liquid–liquid extraction combined with UPLC–MS/MS for the detection of typical Alternaria toxins in pear paste

“…Although the water was able to elute some of the sugars, the methanol eluate still contained a significant amount of sugars and pigments. These water‐soluble pigments are produced by the Maillard reaction during the production of pear paste 37 . Water‐soluble pigments cannot be absorbed by graphitized carbon black.…”

“…These water-soluble pigments are produced by the Maillard reaction during the production of pear paste. 37 Water-soluble pigments cannot be absorbed by graphitized carbon black. To minimize the interference of sugars and pigments on the assay, an attempt was made to dissolve the pear paste into water and extract the target with acetonitrile.…”

Enriching the Bioactive Components and Antioxidant Capacity of Concentrated Lime Juices Prepared by Cryogenic and Vacuum Processes

“…Vacuum-concentrated beetroot juice at 50 and 55 °C increased DPPH inhibition by 18% but remained unchanged when the temperature increased to 60 °C [14]. Similarly, Li, et al [13] found that vacuum-concentrated pear paste increased in DPPH scavenging with the applied temperature in the range of 55 and 60 °C, then gradually decreased when the temperature increased from 65 to 75 °C. The changes in antioxidant ability would involve the cumulative of potentially anti-oxidative components in the juices.…”

“…Freeze-concentrated juices were 15.67% higher in DPPH inhibition compared to vacuum-concentrated juices (t(11) = 19.3012, p < 0.0001). Freeze concentration caused an increase in the anti-oxidative activity of various concentrated products such as apple [20], blueberry [63], and orange [21] juices, as well as pear paste [13]. The increase in the DPPH scavenging activity would be contributed by a great improvement in anti-oxidative components such as ascorbic acid, TPC, and flavonoids found in freeze-concentrated lime juices.…”

“…Vacuum concentration using mild heat for water removal is an alternative technique for reducing phytochemical loss. Disadvantages involving this process may include thermal change of organoleptic and rheological characteristics [13,14]. However, the effects of this kind of evaporation on applying lime juice concentrate's bioactives have not been fully investigated yet.…”