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Experiment of quality properties of dehydrated fruits
Published October 10, 2008
7-15

The lyophilization is the joint application of freezing and drying. It is an up-to-date conserving procedure, the point of which is that the humidity existing in the frozen humid material is transferred from the solid state directly into the gaseous state at a temperature below 0 oC under vacuum. Out of the procedures applied nowadays, this is ...the most tolerant drying process.
With regard to the high investment and operational costs, freeze drying is applied only for valuable, heat-sensitive materials when the technological aim is to preserve such properties as aroma, taste and colour as well as such components as proteins and vitamins. This procedure is suitable for drying and conserving certain foodstuffs, stimulants, organic chemicals, medicines and similar sensitive and valuable materials.
In our institute, we have been conducting freeze drying experiments with regional fruits and vegetables since the year 2005. During the first phase, we examined the heat- and material transfer as well as the abstraction of humidity, while during the second phase we analysed the rehydration ability and nutrient content of the freeze-dried materials as compared to those dried with the method of convection. Moreover we have conducted penetration measurements with a portable hardness tester.
To sum up the results gained so far, we can state that the quality of the lyophilized materials is better than those dried in the traditional way. It originates partly in the fact that the temperature and pressure applied for the freeze drying are smaller and the drying period is far longer than for the convection drying.
In contrast to convection-dried materials, freeze dried materials set in close to their original water-content, keep their original shape and size after being rehydrated. The reason of it the porous, spongy structure (flexible cell wall) of the lyophilized products which is able to take up moisture quickly. In addition, the lyophilized products can be rehydrated faster than those dried in the traditional way.
Regarding the results of the chemical analyses, the following conclusion can be drawn: the vacuum freeze drying results a small decrease of nutrient content and nutritive value for the lyophilized products.
The results of the hardness tests support the statement that the majority of agricultural materials cannot be considered as an ideal flexible body, because during the experiment the flexibility coefficient changed when going from the surface of the material inwards. In addition, the penetration tests also confirm that the surface of the convection-dried vegetables is at least 1.5-3 times harder than that of the freeze-dried products. The reason of it that it takes place during the drying denaturation processes.
The article summarizes the results of our research work listed above, in accordance with our experiments conducted by using the characteristic fruits (apple, plum) of the Nyírség Region.

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Change of antioxidant compounds of spices during drying
Published December 15, 2019
77-81

Spices and herbs have been used by humanity for thousands of years, so they are very important plants.

In this study, the change of dry matter content and antioxidant compounds of eight spices (basil, thyme, rosemary, mint, parsley, lemongrass, chives, coriander) have been examined the raw plants and in plants preserved by three differe...nt drying methods (an oven in 50–60°C; drying at room temperature; lyophilisation between -40 and -50°C, under pressure), because we wanted to see the change of the parameters.

The water content of raw plants was very high, i.e. the dry matter content was very low. By the application of the three drying methods nearly 100% of the water has left the plants, with the exception of the lyophilized basil and rosemary.

Based on the results related to the original material, lyophilized has proved to be the best treatment for the preservation of antioxidant compounds, however air drying also showed high results for some spices.

 

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Evaluation of decreasing moisture content of different maize genotypes
Published June 30, 2018
147-151

An experiment was conducted to evaluate the decrease in grain moisture content in three maize hybrids in Debrecen in 2017. Armagnac, Sushi and Loupiac were the examined hybrids in this study. The culture medium and temperature conditions were applied uniformly for all three hybrids. According to the results obtained from the ratio of moisture c...ontent of seeds per day, the Armagnac variety in the intensive drying down phase loses more time and moisture content, so it can be concluded that the produced dry matter is more than in the case of other varieties. Armagnac requires more time to achieve yield, while the Sushi and Loupiac hybrids produce less harvest. Regarding the slope of the regression line, the rate of loss of moisture in the grain has been negatively correlated with the amount of “b” in the three examined hybrids. In regression analysis, the coefficient of explanation showed that the effect of day in the Armagnac was 97% in the Loupiac, 95% and in the Sushi 90% of the total dynamic value of moisture motion.

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Determining factors of test weight in maize (Zea mays L.)
Published November 15, 2007
40-42

Most domestic maize production products are sold on markets abroad. Among the increasingly restrictive quality requirements, the demand for the measurement of test weight has also appeared. This measurement is not unfamiliar in the case of other cereals, such as wheat and barley, but it has not been applied widely in maize. It is likely for thi...s reason that we have such little information and research available on this topic. In this study, we show the current state of this field with references from domestic and international literature.
The density of maize is the weight of a particular volume and the most frequent unit is the test weight (kg/hl). This physical quality factor plays important roles in the storage, transport and mill industries. The value of test weight is influenced by many factors. The most important ones are the moisture content of grains, drying temperature, drought, precipitation, early frost, and the hybrid characters of a given genotype (grain type, FAO number). In general, the grain with higher moisture content has lower test weight and the higher temperature during (above 82°C) desiccation also leads to unfavourable values. Factors such as a drought interval after flowering, early frost in the case of hybrids with higher FAO numbers, injuries by insects, as well as fungal infections also influence the structure and moisture content of the maize grain.
In the future, broader studies (hybrid testing, application of new agrotechnical elements) will be needed for understanding of the factors effecting test weight.

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Evaluation of dry matter accumulation of maize (Zea mays L.) hybrids
Published June 30, 2018
35-41

The increase of the grain yield of maize is closely correlated with its seasonal dry matter accumulation. Dry matter is accumulated into the grain yield during the grain filling period. The following maize hybrids were involved in the experiment: Armagnac FAO 490, Loupiac FAO 380 and Sushi FAO 340. In order to determine dry matter content, two ...samples per week were taken on the following days: 22nd, 25th, 28th, 31st August, 4th, 7th, 14th, 18th, 22nd, 25th, 29th September and 2nd, 6th, 9th, 13th October. In the course of sampling the weight of 100 grains from the middle section of 4 ears was measured in 4 replications. Dry matter content was determined after drying to constant weight in a drying cabinet at 60 °C. Harvesting was performed on 13th October 2017.

The daily precipitation sum was determined by local measurements, while the daily radiation and temperature data were provided by the Meteorological Observatory Debrecen of the National Meteorological Service in Budapest. Among the agrometeorological parameters, an analysis was made of the precipitation during the growing season, effective heat sums during the vegetative and generative phase, and the water supplies. The daily heat sums were determined using the algorithm proposed.

The amount of precipitation in the winter period before the 2017 growing season was 210 mm. The soil was saturated until its field capacity. The rather dry and warm March and April had a favourable effect, but there was no worthy amount of precipitation until May (51 mm) due to the condition of the dried seedbed. Sowing was performed on the 5th of May 2017 in a randomised small plot experiment. There was favourable precipitation and temperature during the growing season, thereby providing ideal conditions for maize development, growth and yield formation. There was near average amount of precipitation in each year. The total amount of precipitation in the summer period is 342 mm. Temperature was mostly above the average, but there was no long and extremely warm period.

The Armagnac hybrid reached its highest dry matter mass 126 days after emergence. Physiological maturity was reached sooner (on the 119th day) in the case of Loupiac, and even sooner in the case of Sushi (116th day). The thousand grain weight of Sushi (which has the shortest ripening period) was 286 g at the time of physiological maturity, while that of Loupiac was 311 g. Compared to Sushi, Armagnac showed 12 g more dry matter accumulation (306 g). In the case of all three examined hybrids, physiological maturity was preceded by an intensive phase, when the dynamics of dry matter accumulation was rather quick. On average, Sushi gained 2.8 g dry matter per day between 103 days following emergence and physiological maturity, while the same values were 3.2 g for Armagnac and 3.3 g for Loupiac. The aim of the regression line slope is to predict the behavior of the dependent variable with the knowledge of the values and characteristics of the independent variables using the regression line equation. Furthermore, to determine how the location affected the dynamic of dry matter accumulation in the Armagnac, Loupiac and Sushi hybrids. In regression analysis, the coefficient of explanation showed that the effect of day in the Armagnac was 97%, in the Loupiac 94%, in the Sushi 90 %. The determination coefficient (R2) is useful in determing how the regression equation fits. But, as we have seen, the determination coefficient alone is not sufficient to verify the model’s accuracy, in addition to the determination coefficient (R2), the normality of the data or the residuals, the variance of the variables at different levels, the independence of the data relative to time and non-oblique. Observations are evaluated for the correctness of the fitted model.

Dry matter values decreased evenly and slightly following physiological maturity. According to our research results, it was established that physiological maturity is followed by a moderate dry matter loss. Until harvesting, Armagnac lost 40 g of its thousand mass weight in 29 days, while the same value pairs were 69 g in 36 days for Loupiac and 29 g in 39 days for Sushi. Loupiac – which had the highest weight at the time of physiological maturity – lost the most of its dry weight; therefore, Armagnac and Sushi had higher values at the time of harvesting.

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