Volatile compounds from two pineapples varieties (Tainong No.4 and No.6) were isolated by headspace solid phase microextraction (HS-SPME) and identified and quantified by gas chromatography-mass spectrometry (GC/MS). In the Tainong No. 4 and No. 6 pineapples, a total of 11 and 28 volatile compounds were identified according to their retention time on capillary columns and their mass spectra, and quantified with total concentrations of 1080.44 μg·kg−1 and 380.66 μg·kg−1 in the Tainong No.4 and No. 6 pineapples, respectively. The odor active values (OAVs) of volatile compounds from pineapples were also calculated. According to the OAVs, four compounds were defined as the characteristic aroma compounds for the Tainong No. 4 pineapple, including furaneol, 3-(methylthio)propanoic acid methyl ester, 3-(methylthio)propanoic acid ethyl ester and δ-octalactone. The OAVs of five compounds including ethyl-2-methylbutyrate, methyl-2-methylbutyrate, 3-(methylthio)propanoic acid ethyl ester, ethyl hexanoate and decanal were considered to be the characteristic aroma compounds for the Tainong No. 6 pineapple.

An analytical method of solid-phase microextraction (SPME) was developed for pineapple aroma volatile compounds. Different sample preparation procedures involving SPME fibres, including the addition of sodium chloride, extraction time, and temperature, were evaluated to optimise the method. For the optimised method, 6.5 g of ground pineapple flesh was placed in a 20 mL headspace vial with 1 g of sodium chloride; a 65 μm polydimethylsiloxane/divinylbenzene fibre was used for extraction at 50°C for 40 min with continuous stirring. The method was validated by determining its repeatability and recovery. The relative standard deviations for the pineapple aroma compounds were 5.48-11.02%. The average method recovery was 99.13%. The results demonstrate that this SPME procedure is suitable as a simple, rapid, and solvent-free extraction technique for the analysis of pineapple aroma volatile compounds. Using this method, 15 volatile compounds were identified, and the amount was 1019.78 μg.kg−1 in pineapple cv. Shenwan, including seven esters, one terpene, two aldehydes, one ketone, two lactones, one alcohol, and one hydrocarbon. A tentative study to estimate the contribution of the identified compounds to the aroma of the pineapple variety based of their odour activity values indicated four compounds that were characteristic aroma compounds, including methyl hexanoate, δ-octalactone, decanal, and geranyl acetone.

No abstract

This study proposed and evaluated a novel and scalable process based on enzymatic hydrolysis for the preparation of α-amylase inhibitor (α-AI) in seeds of white kidney bean (Phaseolus vulgaris). The process mainly involved heat treatment (70°C/30 min), enzymatic hydrolysis, isoelectric precipitation and 70% ethanol precipitation. The optimal preparation parameters for enzymatic hydrolysis and isoelectric precipitation were as follows: Flavourzyme 500MG was used for enzymatic hydrolysis and the ultimate hydrolysate was obtained at 180 min, followed by isoelectric precipitation at pH 3.6. The loss of miscellaneous proteins and purification fold in the novel process were relatively low (85.84% and 4.74, respectively), while the α-AI activity yield (67.12%) was much higher than the values obtained by chromatography. Combined with the SDS-PAGE analysis, enzymatic hydrolysis proved to have modified the pI and alcohol-solubility of the miscellaneous proteins, which has a favorable influence on isoelectric precipitation and ethanol precipitation for the preparation of the α-AI.