Zhengfu Wang

Characteristics of Thin-Layer Infrared Drying of Apple Pomace With and Without Hot Air Pre-drying

Thin-layer infrared drying characteristics of apple pomace, with and without hot air pre-drying, were studied with a laboratory scale infrared dryer. Moreover, ten commonly used mathematical models were used to fit experimental data. Logarithmic model and Page model were most adequate in describing thin-layer drying of fresh and pre-treated apple pomace respectively. The values of average effective diffusivity in drying the pre-treated apple pomace were about 1.3 times of that in the fresh apple pomace with the initial moisture content of 40% (wet basis).The values of activation energy of moisture diffusion were about 30 kJ/mol for the fresh and pre-treated apple pomace respectively. Infrared drying, combined with hot air pre-drying, can save 20% of drying time to remove the same amount of remained moisture as compared to the infrared drying alone. The above findings might be used for operation of drying apple pomace.

Comparison of different drying methods on Chinese ginger (Zingiber officinale Roscoe): Changes in volatiles, chemical profile, antioxidant properties, and microstructure.

Nowadays, food industry is facing challenges in preserving better quality of fruit and vegetable products after processing. Recently, many attentions have been drawn to ginger rhizome processing due to its numerous health promoting properties. In our study, ginger rhizome slices were subjected to air-drying (AD), freeze drying (FD), infrared drying (IR), microwave drying (MD) and intermittent microwave & convective drying (IM&CD). Quality attributes of the dried samples were compared in terms of volatile compounds, 6, 8, 10-gingerols, 6-shogaol, antioxidant activities and microstructure. Results showed that AD and IR were good drying methods to preserve volatiles. FD, IR and IM&CD led to higher retention of gingerols, TPC, TFC and better antioxidant activities. However, FD and IR had relative high energy consumption and drying time. Therefore, considering about the quality retention and energy consumption, IM&CD would be very promising for thermo sensitive material.

Physicochemical Characteristics of Orange Juice Samples From Seven Cultivars

Some physicochemical parameters of orange juice from seven orange varieties (Pineapple orange, Hamlin, Trovita, Jincheng, 1232 Tangor, Olinda Valencia, and Delta Valencia) were analyzed, special attention was paid to the level of sugars, organic acids, free amino acids, mineral composition, and color parameters. The results showed that total soluble solids (TSS), TSS/titratable acidity (TA) ratios, sugars, and organic acids were kept within a proper range for juice processing except that Jincheng had lower TSS than the others. Sucrose was the most dominant sugar in the orange cultivars, followed by fructose and glucose, while citric acid was the principal organic acid. Serine and proline were the principal amino acids. Potassium was the most abundant mineral in all of the juice samples, followed by magnesium and calcium. The sodium content of most varieties was under 10 mg kg−1. Though all of the samples had orange colour, Olinda Valencia and Delta Valencia had deeper red colour than the others. Statistically significant differences (P<0.05) were found between the samples in most of the characteristics. The results provided important information on the physicochemical characteristics of the varieties and on how to make the best use of orange cultivars for different purposes, which is of significance for both technological research and processing practice.

Extraction of anthocyanins from red cabbage using high pressure CO2.

The extraction kinetics of anthocyanins from red cabbage using high pressure CO(2) (HPCD) against conventional acidified water (CAW) was investigated. The HPCD time, temperature, pressure and volume ratio of solid-liquid mixture vs. pressurized CO(2) (R((S+L)/G)) exhibited important roles on the extraction kinetics of anthocyanins. The extraction kinetics showed two phases, the yield increased with increasing the time in the first phase, the yield defined as steady-state yield (y(*)) was constant in the second phase. The y(*) of anthocyanins using HPCD increased with higher temperature, higher pressure and lower R((S+L)/G). The general mass transfer model with higher regression coefficients (R(2)>0.97) fitted the kinetic data better than the Ficks second law diffusion model. As compared with CAW, the time (t(*)) to reach the y(*) of anthocyanins using HPCD was reduced by half while its corresponding overall volumetric mass transfer coefficients k(L)xa from the general mass transfer model increased by two folds.

Effect of Osmotic Dehydration with Pulsed Vacuum on Hot-Air Drying Kinetics and Quality Attributes of Cherry Tomatoes

The effects of osmotic dehydration (OD) with or without pulsed vacuum (PV) on hot-air drying kinetics and quality attributes of cherry tomatoes were investigated. Both OD and PVOD pre-treatments were performed for 3 h at 50°C in 50 and 70o Brix sucrose solutions with a solution-to-fruit mass ratio of 4:1, and PVOD was applied for 15 min before OD at atmospheric pressure. Samples were further dried at air temperature of 70°C. Effective moisture diffusivity (D eff) of osmotically dehydrated samples increased gradually while the Deff curve of fresh samples had a plateau stage during hot air drying. Lower glass transition temperature, Tg, values of osmotically dehydrated samples indicated that they needed a lower storage temperature. Both OD and PVOD pre-treatments had advantages in shortening drying cycles and improving quality of products. Compared with air drying, osmo-air drying decreased the total drying time, color change, and hardness of dried samples by 32.26%, 18.11%, and 88.21%, respectively, and increased volume ratio and vitamin C retention rate by 72.31% and 125.82%. As compared with OD, PVOD decreased color change and hardness by 28.48% and 45.17%, increased volume ratio and vitamin C retention rate by 27.41% and 17.77%, but there was no significant difference shown in drying time. Therefore, osmotic pre-treatment can shorten the total dehydration time, and improve the general quality of dried cherry tomatoes.

Effective Diffusivities and Energy Consumption of Whole Fruit Chinese Jujube (Zizyphus jujuba Miller) in Microwave Drying

Microwave drying of whole fruit Chinese jujube was performed at 45, 90, and 135 W. Ten commonly used mathematical models of thin-layer drying were compared. The Midilli model was best in describing drying time dependency of product moisture ratios. The initial drying rate and drying rate constant are linearly proportional to microwave power level. An effective diffusivity model was presented and validated with the Renka-Cline algorithm. The model has very high predictive precision, suggested by the relative percentage error of 3.734% on average between the model and the Renka-Cline algorithm. The effective diffusivity was proved to be a linear function of microwave power level and a quadratic function of moisture content. Energy consumption in microwave drying of Chinese jujube decreased as microwave power increased from 45 to 135 W, but 90 W was adequate for high-quality products with less energy consumption.

Effect of Heat Stress During Grain Filling on Phosphoenolpyruvate Carboxylase and Ribulose-1,5-bisphosphate Carboxylase/Oxygenase Activities of Various Green Organs in Winter Wheat

In two winter wheat (Triticum aestivum L.) cultivars differing in their response to high temperature, JD8 (tolerant) and J411 (sensitive) we studied the effect of heat stress on the activities of phosphoenolpyruvate carboxylase (PEPC) and ribulose-1,5-bisphosphate carboxylase (RuBPC) in green organs during grain-filling. There were significantly higher PEPC activities and lower RuBPC activities in each of the non-leaf organs (awn, glume, lemma, peduncle, and sheath) than in the flag leaf blade. Under heat stress for 12 d, the activity of RuBPC quickly declined and the activity of PEPC first increased and later declined in all organs, resulting in a great increase of the PEPC/RuBPC ratios in the organs, particularly in non-leaf organs which had a higher PEPC/RuBPC than the flag leaf blade in all times. The PEPC activity and PEPC/RuBPC ratio in every organ of JD8 were higher than those in the same organ of J411. Thus the differences in PEPC activities and PEPC/RuBPC may be associated with the differences in photosynthetic heat tolerance among the organs of the same plant or between the two cultivars.

The Effect of Freezing Modes and Frozen Storage on Aroma, Enzyme and Micro-organism in Hami Melon

The effects of freezing modes and time in frozen storage on aroma, enzymes and micro-organisms in Hami melon, also called cantaloupe melon (Cucumis melo. var. reticulatus Hami melon), were determined. Freezing process and frozen storage could not significantly reduce either micro-organisms counts or the enzymatic activities of polyphenoloxidase (PPO), peroxidase (POD) and lipoxidase (LOX) in melon. Liquid nitrogen ultra-rapid freezing maintained most aromatic components of the melon as compared with slow freezing. The mechanism of aromatic change in frozen melon was mainly ascribed to esters changing continuously in variety and concentration because of enzymolysis or synthetic reactions of esters catalysed by LOX. Meanwhile, increasing concentration of linoleic acid and linolenic acid in frozen melon cells promoted the biochemical reaction of unsaturated fatty acids in LOX system, so that enzymolysis of the double bonds in the ninth and tenth carbon of linoleic acid and linolenic acid was accelerated. Consequently, with the prolongation of time in frozen storage more and more unsaturated alcohols and aldehydes with 6 and 9 carbons were produced, the green notes of frozen storage melon became more and more intense, and the ester fragrance became more and more feeble. The above findings can benefit the development of cantaloupe melon process industry.

Identification and quantification of anthocyanins in Kyoho grape juice‐making pomace, Cabernet Sauvignon grape winemaking pomace and their fresh skin

BACKGROUND The anthocyanins of Kyoho grape juice-making pomace, Cabernet Sauvignon grape winemaking pomace and their fresh skin were identified and quantified by high-performance liquid chromatography-tandem mass spectrometry, and the influence of processing on the anthocyanin profiles was investigated. RESULTS Twenty-three and 16 anthocyanins were found in fresh skin of Kyoho and Cabernet Sauvignon grapes, respectively. Malvidin 3-(trans)-coumaroyl-5-diglucoside and malvidin 3-glucoside were the most abundant anthocyanin in fresh skin of Kyoho and Cabernet Sauvignon grapes, respectively. The cis and trans isomers of malvidin 3-coumaroyl-5-diglucoside are reported in Kyoho grape for the first time. In addition, the anthocyanin content of juice-making pomace of Kyoho grapes and winemaking pomace of Cabernet Sauvignon grapes was significantly lower than the fresh skin samples (p < 0.05). The percentage variation of non-acylated anthocyanins was lower than that of acylated anthocyanins in all pomace samples. CONCLUSION Kyoho grape and Cabernet Sauvignon grape showed distinctive anthocyanin profiles. Juice-making pomace is a better source of anthocyanins for use in functional foods than winemaking pomace.

Effect of dehydration methods on antioxidant activities, phenolic contents, cyclic nucleotides, and volatiles of jujube fruits

Changes in antioxidant activities, phenolic contents, cyclic nucleotides, and volatiles of jujube after dehydration using freeze-drying (FD), air drying (AD), sun drying (SD), and microwave drying (MD) were investigated. All dehydration methods caused a decrease in antioxidant activities, aldehyde, acid, and alkane contents. Esters were increased by the dehydration. FD was superior to other dehydration methods for retention of total phenolics, total flavonoids, and antioxidant activities. MD caused an increase of catechin and epichtechin levels. Although AD, MD, and SD caused declines in cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) contents, AD at 50oC was a good choice to obtain jujubes with high levels of cAMP and cGMP. Theoretical fundamentals for selection of suitable drying techniques to minimize the negative effects caused by dehydration and for meeting production requirements are provided.