Effects of different processing steps on the flavor and colloidal properties of cloudy apple juice.

Flavor loss is a common problem when manufacturing apple juice and is closely related to the properties of the colloidal pectin particles in cloudy juice. The flavor changes and particle properties of three varieties of apple juice ('Ralls', 'Golden Delicious' and 'Fuji') during processing were investigated. Compared with manually pressed juice, juice made by industrial pulping and filtration contained larger particles, resulting in the 'sweet and sour' taste of the juice being relatively weak and the diversity of aromas narrower, as determined by E-nose analysis. Pulping and filtration, however, released some important flavor esters, such as butyl butyrate, hexyl-2-methyl butyrate, and hexyl butyrate. The transformation of volatile compounds during apple juice processing was closely related to the apple cultivar but, in all three varieties, the content of 1-hexanal and (E)-2-hexenal in the juice gradually decreased during processing. Pectinase treatment reduced the colloid particle size and increased the ζ-potential of the juice, resulting in better uniformity and stability, as well as increasing the content of nonanal. After pasteurization, the colloidal particles tended to aggregate and the ζ-potential decreased. Many volatile compounds decreased in concentration or disappeared after heat treatment. The flavor and colloidal properties of cloudy apple juice changed markedly during processing and the effect of each processing step was different. © 2020 Society of Chemical Industry.

Zhu D ，Kou C ，Shen Y ，Xi P ，Cao X ，Liu H ，Li J ... -  《-》

Effect of particle size on the stability and flavor of cloudy apple juice.

Different particle sizes in cloudy apple juice were obtained following filtration with different mesh sizes (100, 200, 300, and 400-mesh). The effects of cloud particle size on the stability, nutrient content, and volatile flavor of cloudy apple juice were evaluated. With increasing mesh number, particle size decreased (p < 0.05) and particle shape changed. Particle size had an effect on volatile flavor compounds, especially nitrogen oxides, alcohols, and aromatic compounds. The content of pectin and total phenol decreased with decreasing particle size, while the content of soluble protein was not affected. The reduction of cloud particle size increased absolute value of ζ-potential, cloud stability, and apparent viscosity and decreased turbidity and cloud values. Pearson correlation analysis showed that there was a strong correlation between particle size and quality indicators, except for soluble protein.

Zhu D ，Shen Y ，Wei L ，Xu L ，Cao X ，Liu H ，Li J ... -  《-》

Characterization of ester odorants of apple juice by gas chromatography-olfactometry, quantitative measurements, odour threshold, aroma intensity and electronic nose.

In this study, twenty ester compounds of juiced apples from three different varieties were identified and quantified by gas chromatography-olfactometry (GC-O) and gas chromatography-mass spectrometry (GC-MS) analysis. Six esters were selected as the key odour-active compounds by omission Tests. Perceptual interaction among esters was investigated through odour thresholds and intensity of six esters and fifteen binary mixtures. Most of these mixtures followed an addition behavior. Ethyl butanoate and butyl acetate had a synergistic effect. Sensory analysis revealed that fruity, sour and green notes were enhanced significantly by adding the binary mixture of ethyl butanoate and butyl acetate (E&B). Electronic nose (e-nose) data showed that, compared with the individual ester, the response values of E&B were increased on four sensors. Moreover, with regard to partial least squares regression (PLSR), fruity, sour and green notes attribute covaried well with five sensors of e-nose. The present study would provide a theoretical basis for understanding the aroma characteristic of apple juice, hoping to be helpful for the improvement of apple juice aroma and flavour.

Niu Y ，Wang R ，Xiao Z ，Zhu J ，Sun X ，Wang P ... -  《-》

Minimizing quality changes of cloudy apple juice: The use of kiwifruit puree and high pressure homogenization.

Cloud loss, enzymatic browning, and flavor changes are important quality defects of cloudy fruit juices determining consumer acceptability. The development of clean label options to overcome such quality problems is currently of high interest. Therefore, this study investigated the effect of kiwifruit puree (clean label ingredient) and high pressure homogenization on quality changes of cloudy apple juice using a multivariate approach. The use of kiwifruit puree addition and high pressure homogenization resulted in a juice with improved uniformity and cloud stability by reducing particle size and increasing viscosity and yield stress (p < 0.01). Furthermore, kiwifruit puree addition reduced enzymatic browning (ΔE∗ < 3), due to the increased ascorbic acid and contributed to a more saturated and bright yellow color, a better taste balance, and a more fruity aroma of juice. This work demonstrates that clean label options to control quality degradation of cloudy fruit juice might offer new opportunities.

Yi J ，Kebede B ，Kristiani K ，Grauwet T ，Van Loey A ，Hendrickx M ... -  《-》

Light-induced off-flavor development in cloudy apple juice.

Hashizume M ，Gordon MH ，Mottram DS 《-》