Moderate heat treatments enhance the quality of traded natural shea butter

Abstract

Natural shea butter (NSB), extracted by traditional methods resulting in its poor quality, is nevertheless widely traded within Africa and beyond due to its several useful applications. This study examined effects of simulated laboratory/domestic heat treatments on quality of the commodity obtained from a cross section of Nigerian markets. Physicochemical and microbiological qualities of NSB samples procured from four selected  markets located across three Nigerian states were evaluated by standard methods before and after graduated thermal stress treatments from 50 through 120 °C over 5, 15, or 30 min durations, respectively, and filtration at 60 °C. Mean physicochemical quality values of NSB samples determined, namely: specific gravity at 29 °C (0.90-0.94); softening, melting temperatures (33-36, 36-39 °C; respectively); acid, iodine, and saponification values (10.5- 29.3, 46.4-59.1, 110-470; respectively), were not adversely or significantly altered by the thermal treatment types and stresses. Whereas all untreated NSB samples demonstrated microbial contamination (total viable counts: 3 6 10 -10 cfu/g) with Pseudomonas, Klebsiella, Staphylococcus, Bacillus, Aspergillus, or Candida species, the graduated heat treatments produced varied sanitizing effects. Higher temperatures (100, 120 °C) gave greater and more rapid cleansing action than the lower temperatures (50, 75 °C), both intensity-ranges being aided by length of holding time. Hot filtration eliminated all the NSB contaminants. In conclusion, while untreated NSB is found grossly contaminated by microbes, unhygienic and unsafe for human use, this study has demonstrated efficient contaminants-cleansing action of heat treatments (³100 °C × ³ 30 min) on NSB, and the total sanitizing effect of hot filtration process.

Key words: Natural shea butter, Physicochemical quality, Microbiological quality, Heat treatment, Hot filtration.