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United States Department of Agriculture

Agricultural Research Service

Research Project: New Sustainable Processing Technologies to Produce Healthy, Value-Added Foods from Specialty Crops and their Co-Products

Location: Healthy Processed Foods Research

Title: Size and moisture distribution characteristics of walnuts and their components

item Khir, Ragab
item Pan, Zhongli - John
item Atungulu, Griffiths
item Thompson, James
item Shao, Ongyan

Submitted to: Food and Bioprocess Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2011
Publication Date: 11/23/2011
Publication URL:
Citation: Khir, R., Pan, Z., Atungulu, G., Thompson, J., Shao, O. 2011. Size and moisture distribution characteristics of walnuts and their components. Food and Bioprocess Technology. DOI: 10.1007/s11947-011-0717-1.

Interpretive Summary: Different varieties of walnuts were characterized for their size and moisture distributions. A wide range of walnut sizes and moisture contents were found. The average moisture content of walnuts with hulls was higher than that of walnuts without hulls. This information is important to improve efficiency of handling and processing equipment used to dry high quality walnuts in an energy efficient manner.

Technical Abstract: The objective of this study was to determine the size characteristics and moisture content (MC) distributions of individual walnuts and their components, including hulls, shells and kernels under different harvest conditions. Measurements were carried out for three walnut varieties, Tulare, Howard and Chandler cultivated in California, USA. The samples for each variety were collected from the harvester at the first and second harvest of nuts treated with and without Ethephon. The nuts were sorted into two categories as with hulls and without hulls before conducting dimension and MC measurements. The results showed that there was a wide range of size distribution for nuts with and without hulls and a huge variability in moisture content among individual nuts at harvest. The average MC of nuts with hulls was much higher than that of nuts without hulls for all tested varieties. The nuts with hulls had an average moisture content of 32.99% compared to 13.86% for nuts without hulls. Also, the shell moisture content was much higher than kernel moisture content. On average, the differences in moisture content between shell and kernel was 11.56% for nuts with hulls and 6.45% for nuts without hulls. There was no significant deference in hull MC between the first and second harvest for the studied varieties. Based on the regression analysis, it was observed that strong relationships exist between the MC of shells and kernels. The obtained results provide information for designing and developing new handling and processing equipments, especially for increased drying capacity, reduced energy use and obtaining high quality walnut products.

Last Modified: 10/17/2017
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