Efficacy of cloves (Syzygium aromaticum) and ginger (Zingiber officinale) extracts against microbial spoilage of locally produced soymilk at ambient storage

There is a global concern at present with the use of synthetic chemical preservatives in foods due to carcinogenic and mutagenic related problems, resulting to the use of natural preservatives especially culinary herbs and spices in food products. Herein, efficacy of clove (Syzygium aromaticum) fruit and ginger (Zingiber officinale) rhizome was evaluated against rapid deterioration of locally produced soymilk at ambient storage by microorganisms and their bioactive compounds determined with gas chromatography and mass spectrometry (GC-MS). Interestingly, soymilk treated with 5% ginger extract among other tested concentrations had the least bacterial (2.00±0.50 ×104 cfu/ ml) and fungal (2.00±0.00 ×104 sfu/ml) counts that did not exceed the acceptable limit for pasteurized milk (3 ×104 cfu/ ml) by day 3 of storage when compared with untreated soymilk that recorded very high bacteria (56.50±6.50 ×104 cfu/ml) and fungi (13.50±1.50 ×104 sfu/ml) counts. The efficacy could be traced to beta-amyrin (24.15%), hexadecanoic acid (15.71%) and phytol (16.55%) that are major bioactive compounds detected in the ginger extract. Thus, the ginger extract offers prospect as promising alternative that can be applied in extending the shelf life of soymilk and other liquid processed foods.