Effect of Potash Alum on the Mycoflora of Postharvest Spoilage of Solanum lycopersicum L (Tomato)

Solanum lycopersicum L (Tomato) is one of the most economically attractive and widely consumed
vegetables globally. Their high water content, perishability, transport and poor storage system
predisposes them to spoilage by a broad spectrum of mycoflora resulting in huge postharvest losses.
This study investigates the effect of Potash Alum (PA) on postharvest spoilage of S. lycopersicum L
(Tomato). Composite samples of deteriorating tomatoes were subjected to standard mycological
analysis from which total fungal colony counts obtained ranged from 1.64x106-5.70x109 CFU/g, and
the following species were identified; Aspergillus niger, A. flavus, Fusarium sp, Penicillium sp,
Rhizopus stolonifer, Geotrichum candidium and Saccharomyces cerevisiae. In vitro antifungal activity
of potash alum (1% (w/v) concentration) was determined on some of the isolates by agar well method
(AWM) and diameter of inhibition zone (DIZ) measured using a metre rule. G. candidum had the
highest DIZ (9.0mm (29.0%) followed by A. niger (8.0 mm (25.8%) and 7.0mm ( 22.6%) for Fusarium
and Penicillium species respectively. R. stolonifer showed no inhibition or zero. pH values increased
from 4.35-4.52 whereas TTA values decreased from 0.13-0.07 within 2days of analysis. However,
these results indicate that treatment of postharvest deteriorating tomatoes with potash alum prior to
consumption would enhance food safety as some of these fungi are known to be spoilage, toxigenic
or opportunistic pathogens. So, their presence raises concern on storability as well as public health
risks associated with consumption of these fruits. Therefore, production of tomato requires an
integrated and multidisciplinary research approach not only to reduce economic loss but also create
consumers’ awareness on potential public health hazards of consuming relatively cheaper and
pathogen contaminated deteriorating tomatoes.