Effect of relative humidity, storage days, and packaging on pecan kernel texture

Authors: PRABHAKAR, HIMANSHU - University Of Georgia; KERR, WILLIAM L - University Of Georgia; Bock, Clive; KONG, FANBIN - University Of Georgia

Submitted to: Journal of Texture Studies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2022
Publication Date: 9/22/2022
Citation: Prabhakar, H., Kerr, W., Bock, C.H., Kong, F. 2022. Effect of relative humidity, storage days, and packaging on pecan kernel texture. Journal of Texture Studies. 54:115-126. https://doi.org/10.1111/jtxs.12723.
DOI: https://doi.org/10.1111/jtxs.12723

Interpretive Summary: Pecan is an important specialty crop in the US. The pecan nut is variable in structure, and various methods have been proposed to measure pecan texture. Variability in the measurements has been an issue. Furthermore, there are no predictive model to estimate changes in pecan texture during storage. We used novel approaches to study the effects of relative humidity and packaging material (polyethylene [PE], polypropylene [PP], low density polyethylene [LDPE] and metallic laminates [ML]) on pecan texture, and introduced a new rift ratio (fracturability to hardness [F/H] ratio) metric to measure pecan texture to reduce data variability and to develop predictive models for textural changes during storage. The F/H ratio had low variability (R2 = 0.72). The pecans stored at 75% retained a better F/H ratio than those stored at 80% or 90%. The pecans stored in ML retained the best textural attributes compared to those stored in LDPE, PP or PE, suggesting ML is a packaging of choice, but use of any package type delayed loss in F/H. A 3-parameter logistic model was developed to predict texture changes during storage.

Technical Abstract: Despite being one of the most important specialty crops in the US, there have been few studies on the effects of environmental conditions on pecans quality attributes, including changes in pecan texture in the dynamic storage and distribution environment. Pecans are non-uniform and irregular in structure, and various methods have been proposed to measure pecan texture. But most of the methods could not control the variability in the experimental observations of texture. Unlike other tree-nuts and legumes, there are no predictive model to estimate changes in pecan texture during storage. We used novel approaches to study the effects of relative humidity (RH, 30 to 90%) and packaging material (polyethylene [PE], polypropylene [PP], low density polyethylene [LDPE] and metallic laminates) on pecan texture, introducing a rift ratio, which is the fracturability to hardness ratio (F/H), to address variability in the data and to develop predictive models to estimate changes in textural attributes of pecans during storage. The textural analysis was conducted on pecan cores and intact pecans to measure area under the curve, fracturability, hardness, cohesiveness, chewiness, springiness, and F/H. Values of F/H obtained using intact pecan method had a high coefficient of determination (R2 – 0.72) as compared to of the remaining textural attributes. A 3-parameter logistic model was employed to construct a predictive model for pecan texture during storage with and without packaging under different RHs. The pecans stored at 75%, 80% and 90% lost half the initial F/H after approx. 115 days, 3 days, and 0.15 days (~ 4 hours), respectively. The pecans stored in LDPE, PP and PE packs at 80% lost half of the initial F/H after approx. 26 days, 57 days, and 78 days, respectively. Use of any kind of package delayed the loss in F/H by at least 8-fold at 80% RH. The pecans stored in laminates did not experience a significant loss in textural attributes.