Influence of cutting direction of cork planks on the quality and porosity characteristics of natural cork stoppers

A Costa,H Pereira

doi:10.5424/fs/2010191-01166

Abstract

In the industrial production of natural cork stoppers, cork planks are cut transversely into strips and stoppers are bored in the axial direction, therefore with their cylinder axis parallel to the tree axial direction. The influence of cutting direction of cork planks (transverse or longitudinal), and therefore the orientation of stoppers cylindrical axis (longitudinal or tangential, respectively) on yields, quality profile and porosity characteristics was studied in a random sampling of planks of different quality classes that were bored to produce 45 mm × 24 mm stoppers. The stoppers quality profile and production values were not influenced by the cutting direction, although in good quality planks (1st/2nd) the longitudinal cut led to a higher proportion of good quality stoppers in comparison to the transversal cut, 32% vs. 23%. Regarding porosity characteristics, pore orientation differed between the two cutting directions but not the porosity coefficient, with the exception of the poor quality classes.

Highlights

The industrial processing of cork planks for the manufacture of natural cork stoppers can be described by three sequential phases (Pereira, 2007): i) Preparation of cork, where the cork planks, after field and mill yard storage for about 6 months, are immersed in boiling water during 1 hour, dried for 2-3 days, trimmed and separated into cork boards by calliper and quality classes; ii) Production of stoppers, where the graded cork boards are cut transversely into cork strips with an height corresponding to the stopper’s length, the cork strips are bored with cutting cylinders with an inside diameter corresponding to the desired stopper’s diameter and the obtained stoppers are dimensionally rectified by sanding;A
The quality profile of the stoppers obtained from good quality cork boards showed a higher proportion of good quality cork stoppers, independently of the cutting direction
The cork board cutting direction did not alter the general pattern of the stoppers distribution by quality class good cork boards (1st/2nd) showed better

Summary

Introduction

The industrial processing of cork planks for the manufacture of natural cork stoppers can be described by three sequential phases (Pereira, 2007): i) Preparation of cork, where the cork planks, after field and mill yard storage for about 6 months, are immersed in boiling water during 1 hour, dried for 2-3 days, trimmed and separated into cork boards by calliper and quality classes; ii) Production of stoppers, where the graded cork boards are cut transversely into cork strips (called rabanadas) with an height corresponding to the stopper’s length, the cork strips are bored with cutting cylinders with an inside diameter corresponding to the desired stopper’s diameter and the obtained stoppers are dimensionally rectified (tops and the cylindrical body) by sanding;A. In the industrial processing for production of natural cork stoppers two main factors determine its economic feasibility: the yield of production, i.e. the efficiency of raw material use and the quality of the obtained stoppers. Cork is a natural raw material with high heterogeneity and production yield and quality diversity are to be expected. The mass production yield of stoppers is on average less than one quarter of the cork planks that are bored (Fortes et al, 2004), whereas the economic return is directly influenced by the quality of the resulting stoppers, e.g. the price of a good quality stopper can be five times higher than that of a low quality stopper. Good planks yield a larger percentage of stoppers of the best quality classes (Pereira et al, 1994; Beja, 2001)

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Results

Discussion

Conclusion