Raw and Dry Salted Olives
In the table olive processing, salt concentration, temperature and pH
adjustments during fermentation and the use of starter culture increase
the formation of lactic acid, resulting in more delicious and durable
olives (Mcfeeter, 2004; Oliveira et al, 2004; Randazzo et al, 2010;
Irmak, 2015).
TABLE 2 Some physikochemical properties of raw and dry
salted olives
Although the pH values of raw olives were high, with the development of
lactic acid, it decreased at the end of the fermentation. It reached the
final values of pH-4.78 in traditional olives and pH-4.23 in culture
added olives (Table 2). The final pH value reached by starter culture
used indicates a successful lactic fermentation.
The effect of starter culture use on pH and titratable acidity values
was found to be statistically significant (p<0.01). Titratable
acidity of starter culture added olives was found to be higher than
normal production. The pH values of the samples decreased below the safe
pH value of 4.6 after 3 months of processing. The pH decrease in both
olives during processing is mainly due to the production of lactic acid,
the main LAB metabolic product, and the conversion of some phenols on
acids such as the glucoside elenolic acid, which is released after
hydrolysis of oleuropein (Kiai et al., 2020). It is also stated that
other organic acids such as acetic, malic, citric, formic and succinic
contribute to the overall pH.
Parallel to the findings of the study, Benincasa et al. (2015) and Ünal
& Nergiz (2003) mentioned, similar pH values at the end of
fermentation. On the contrary of Benincasa et al. (2015), in particular,
since the starter culture added table olive samples showed higher pH and
titratable acidity content, they did not seem to be affected by
phenolics.
Differences detected in titratable acidity values according to
processing methods showed that processing methods were effective on
titratable acidity value. The change in titratable acidity values
determined depending on the olive processing methods was found to be
statistically significant at the p<0.01 level with the
variance analysis applied on the titratable acidity values obtained from
the olive samples.
As shown in Table 2, the acidity of raw olives was found to 0.46% (as
lactic acid). The dry salting process caused an increase in the acidity
of olive fruits. After fermentation, it increased to the value of 0.54%
and 0.71% in normal and starter culture added samples respectively. The
reason of this increase in the acidity is the lactic asid formed by
lactic acid bacteria.
Parallel to our findings the highest titratable acidity, were determined
at inoculated samples (Kumral and Sahin, 2009). Ünal and Nergiz (2003)
found acidity in black table olives slightly lower than our research
findings (0.45%).
The reducing sugar value of the raw olives was 1.92%. dry salting
method reduced sugar content of olives and determined 0.45% (N) and
0.36% (K) at the end of fermentation. The change in reducing sugar
values depending on the olive processing methods was found to be
statistically significant at the p<0.01 level.
The initial sugar concentration in traditional olives was almost 20%
higher than in starter culture added olives. This may be because, during
the fermentation phase, cultured olives produce higher titratable
acidity and therefore more degradation at sugar levels. It is seen in
our study that the production of more titratable acidity causes the
breakdown of sugars and with it, faster removal of bitterness and a
lower pH development.
The total phenolic compound in the raw olive samples is 389 mgCAE/100g,
the total phenolic substance values of the olive samplesobtained
according to the processing methods are in the normal production and the
cultured production methods 238 and 206 mgCAE/100g, respectively.
Our results showed that processing methods affected the phenolic
contents and they decreased in both olive processing methods. The
phenolic concentration is quite low in olives produced by the culture
added method. Due to the rapid pH and titratable acidity changes during
fermentation, the faster decomposition and diffusion of water-soluble
phenols increases the losses. In traditional production, relatively low
titratable acidity causes less degradation of phenols and may be slower
to pass to the external environment as it affects the fruit peel less.
Besides, we can say that the phenolics in the olive do not adversely
affect the culture inoculated for a rapid fermentation.
The processing method of the final products has also a significant
effect on the phenolic compound concentration. Olive fruit processing
methods affect the taste and can significantly alter the health
properties of the olive fruit, mostly because different processing
methods can lead to different capacity of hydrolysis products (Marsilio
et al., 2005; Zoidou et al., 2010; Charoenprasert & Mitchell, 2012;
Salis et al., 2021). Research results showed that table olive processing
techniques have a significant effect on the total phenolic content of
olives and that the applied processing techniques cause a significant
reduction in the total phenol content of olives (Irmak et al., 2010).
As a result, the level of phenolic compounds of olives decreased during
fermentation and during storage compared to raw fruit. This is also in
line with previous studies (Blekas et al., 2002; Romero et al., 2004;
Irmak et al., 2010; Sahan et al., 2013; Kiai et al., 2020). On the other
hand, polyphenol contents of end products of all studied treatments were
decreased comparing to the traditional one (Abd El-Samie Ibraheem,
2015).
Generally the results of polyphenols were in agreement with those
reported by Marsilio et al. (2006), who reported that, processing of
olive resulted in a 35-40 % loss of total phenols (during 7 months),
where the results indicated that they were lost more during the first 3
months of fermentation. (Abd El-Samie Ibraheem, 2015)
The differences detected in the total phenolic substance values
according to the processing methods showed that the processing methods
were effective on the total phenolic compound value. The change in the
total phenolic matter values determined depending on the olive
processing methods was found statistically significant at the
p<0.01 level with the analysis of variance applied on the
total phenolic matter values obtained from the olive samples (Table 7).
Along with the differences detected in the total phenolic compound
values of the processing methods, the irradiation and storage process
were found statistically significant at the p<0.01 level.
According to the Durante et al. (2018) and Blekas et al. (2002) total
phenol of black olives vary from 10 mg/100 g of flesh to 83.3 mg/100 g
of fresh weight. These results are lower than the results obtained from
our study. This may be due to the different olive cultivars and
processing methods they used. Kiai and Hafidi (2014) stated a
significant loss in the total amount of phenolic substances in olives
during fermentation due to the diffusion of water-soluble phenolic
compounds into the brine, and similar results have been reported by
other researchers (Alvarez et al., 2014; Othman et al., 2009; Romero et
al., 2009).