Pretreatment of palm kernels with proteases modified the volatile flavor compounds of palm kernel oil

Abstract

Three commercial proteases, namely Protamex, Neutrase, and Alcalase were applied to treat palm kernel (PK) powders with the aim to modify the flavor of palm kernel oil (PKO) obtained from roasted PK. The results showed that after protease treatment and roasting, the volatile profile of obtained PKO was significantly modified with more pyrazines and other N‐heterocyclic compounds being formed. Protamex, among others, was especially effective in enhancing the generation of such N‐heterocyclic compounds. Besides, aroma‐active compounds such as benzeneacetaldehyde, 1‐(2‐furanyl)‐ethanone and 5‐methyl‐2‐furancarboxaldehyde were found at higher levels in protease‐treated PKO, whereas the content of 2‐furanmethanol decreased. On the basis of all pyrazines and other aroma‐active compounds, principal component analysis (PCA) clearly separated the protease‐treated PKOs from their respective control, with the volatile profile of PKOs derived from Protamex‐ and Alcalase‐treated PK being the most distinct. Practical applications The flavor quality is an important factor to edible oils which determines their application and acceptability to a large extent. For a long time, PKO is used as non‐flavor related fat base in food areas. The results in this study suggest that it is possible to use proteases to pretreat PK to modulate the flavor of PKO. The improvement in flavor would not only be beneficial for the current utilization of PKO, especially in bakery and confectionery areas, but also widen the scope of its applications. Besides, protease pretreatment combined with the thermal reactions as a novel approach might also be applied to modulate the flavor of other seeds’ oils with or without adaption.

Comparison of solvent systems on extraction, quality characteristics, and volatile compounds of palm kernel oil

“…Roasting increased the number of volatile compounds detected in PKO compared to unroasted PKO (Zhang et al, 2016) due to Maillard reaction, thermal lipid oxidation and degradation, and Strecker degradation and caramelization. Pretreatment with proteases and celluclast also modified the volatile profile of PKO (Zhang et al, 2017; Zhang & Liu, 2018). Of the 50 volatile compounds identified in the PKO samples, 21 (3 esters, 1 acid, 2 aldehydes, 12 hydrocarbons, and 3 ketones) were identified on both columns (Table 4).…”

“…Unlike CNO with a characteristic pleasant tropical odor, PKO may require deodorization or modification to remove the volatile components (Zhang & Liu, 2018). Different methods have been employed to modify the aroma of PKO, including kernel roasting (Zhang et al, 2016), pretreatment with proteases (Zhang & Liu, 2018), and celluclast (Zhang et al, 2017) among others.…”

“…As a result of this property and their oxidative stability, PKO and CNO are used extensively in confectionaries and other edible products (List, 2016; Pantzaris & Ahmad, 2001). PKO is used as a replacement for butterfat, in the production of ice cream, filling creams, toffees and caramels, coffee whiteners, icing, margarine, and serves as a cocoa butter equivalent (List, 2016; Pantzaris & Ahmad, 2001; Zhang & Liu, 2018). Unlike CNO with a characteristic pleasant tropical odor, PKO may require deodorization or modification to remove the volatile components (Zhang & Liu, 2018).…”

“…PKO is used as a replacement for butterfat, in the production of ice cream, filling creams, toffees and caramels, coffee whiteners, icing, margarine, and serves as a cocoa butter equivalent (List, 2016; Pantzaris & Ahmad, 2001; Zhang & Liu, 2018). Unlike CNO with a characteristic pleasant tropical odor, PKO may require deodorization or modification to remove the volatile components (Zhang & Liu, 2018). Different methods have been employed to modify the aroma of PKO, including kernel roasting (Zhang et al, 2016), pretreatment with proteases (Zhang & Liu, 2018), and celluclast (Zhang et al, 2017) among others.…”