تأثیر اندازه ریشه بر خصوصیات مکانیکی و شیمیایی چغندرقند

Extended Abstract
 
Introduction
The economic value of sugar derived from sugar beet primarily depends on the technological quality of the root and the efficiency of sugar extraction methods. Technological quality is defined as a combination of chemical, biological, and physical characteristics that determine the recoverable sucrose yield and consequently influence sugar production costs. Among the physical traits, root elasticity and resistance to cutting are of particular importance as they directly affect root handling and processing efficiency. Root elasticity influences the extent of mechanical damage and breakage during harvesting, storage, transportation, and washing. resistance to cutting plays a crucial role during the slicing stage of processing, determining the ease of cossette formation and sucrose diffusion. A woody root texture increases blade wear, causes irregular cossette thickness, and ultimately reduces sucrose diffusion efficiency in the diffusion process.
 
Materials and Methods
This study was conducted from 2018 to 2020 at the experimental farm of the Sugar Beet Seed Institute, Kamalshahr, Karaj, Iran, to evaluate the physical and chemical characteristics of four commercial sugar beet cultivars. Each year, sowing was performed in May in a 5 × 150 m² plot with a row spacing of 50 cm and a plant density of 100,000 plants per cultivar. The experiment was arranged as a factorial (B × A) based on a randomized complete block design with ten replications. Factor A included four cultivars: IR1 (a₁), IR2 (a₂), IR3 (a₃), and IR4 (a₄), while factor B represented root size, classified into three weight categories: small (<0.5 kg, S), medium (0.5–1.0 kg, M), and large (>1.0 kg, L). In November of each year, after reaching technological maturity, ten random samples were collected from each cultivar, each consisting of 50 individual roots. After weighing, roots were grouped by size, and ten roots per size group were randomly selected for mechanical property assessment (resistance to cutting and elasticity). The remaining roots were analyzed for chemical properties with ten replications. Chemical traits included total sugar content, sodium, potassium, harmful nitrogen, extractable sugar, and molasses sugar. Mechanical tests were performed using an INSTRON HOUNSFIELD universal testing machine. Rectangular specimens (2 × 2.5 × 2.7 cm³) were cut from the crown, middle, and tip sections of the roots. A 5 cm diameter compression cylinder was used for elasticity measurement, while a blade measuring 0.15 × 5.5 × 8 cm³ was used for resistance to cutting testing.
 
Results and Discussion
The average relative distribution of small, medium, and large roots across the three years was as follows: IR1 (49, 39, and 12%), IR2 (55, 34, and 11%), IR3 (32, 43, and 25%), and IR4 (47, 37, and 16%). Analysis of variance revealed significant effects of cultivar, year, and root size on the chemical properties of sugar beet. Extractable sugar content was significantly lower in large roots (>1 kg) than in medium (0.5–1 kg) and small (<0.5 kg) roots (P < 0.05). No significant linear correlation was found between root weight and the elasticity of the central section. Increasing root size resulted in a significant reduction in extractable sugar, confirming that larger roots are less desirable for processing efficiency (P < 0.05). A weak but significant negative correlation was observed between root size and resistance to cutting, described by the regression equation y = -0.0036x + 11.121 with a coefficient of determination R² = 0.18 (P < 0.01). Overall, medium-sized roots (up to 1 kg) were identified as optimal for industrial processing, combining higher sugar content with lower resistance to cutting compared with small and large roots. It is therefore recommended that crop management practices should aim to achieve an average single-root weight of approximately 1 kg.
 
Conclusion
It is recommended that crop management practices should aim to achieve an average single-root weight of approximately 1 kg. Roots of this size not only contain higher sugar content compared with larger sugar beet roots but also and offer lower resistance to cutting than smaller roots. This combination ensures better slicing and enhances sucrose extraction efficiency during the diffusion process in sugar factory
 References
Campbell LG. Sugar beet quality improvement, Journal of Crop Production, 2002; 5:1/2, 395-413. Doi:http://doi.org/10.1300/J144v05n01_16
Schäfer J, Hale J, Hoffmann CM, Bunzel M. Mechanical properties and compositional characteristics of beet (Beta vulgaris L.) varieties and their response to nitrogen application. European Food Research and Technology 2020; 246:2135–2146. Doi:http://doi.org/10.1007/s00217-020-03562-4
Roggo Y, Duponchel L and Huvenne JP. Quality evaluation of Sugar Beet (Beta vulgaris) by Near-Infrared Spectroscopy. Journal of agricultural food chemistry, 2004; 52, 1055–1061. Doi:http://doi.org/10.1021/jf0347214

Each cultivar was grown in 150 × 5 m² plots, and in November, 10 random samples (each sample consisting of 50 roots) were harvested and classified into the three root size groups. Ten roots per each size group were randomly selected for measuring shear strength and elasticity, while the remaining roots were used to determine quality attributes in 10 replicates. Shear strength and elasticity were assessed at three sections of each root (crown, mid-root, and tip) using an INSTRON Hounsfield texture analyzer. he results showed that the average relative frequency of root size distribution over the three-year period was as follows: IR1 — 49% small, 39% medium, 12% large; IR2 — 55%, 34%, 11%; IR3 — 32%, 43%, 25%; and IR4 — 47%, 37%, 16%. Extractable sucrose content was significantly lower in large roots compared to medium and small roots (p < 0.01). Root weight was negatively correlated with shear strength (R² = 0.18) and extractable sucrose percentage (R² = 0.12), while no significant correlation was found between root weight and elasticity (R² = 0.07). In terms of shear strength, cultivar rankings were as follows: IR3 < IR2 < IR1 < IR4, with IR3 exhibiting the lowest resistance. Overall, medium-sized roots were identified as the optimal root size, combining higher sugar content compared with large roots and lower shear resistance compared with small roots, which facilitates slicing and improves sucrose diffusion during processing. It is therefore recommended that crop management practices be directed toward achieving an average single-root weight of approximately 1 kg.