Using Resins to Debitter Olives May Be Eco-Friendly Alternative

Researchers have found a way to remove the bit­ter­ness from olives in a more envi­ron­men­tally-friendly way than com­mer­cially-favored meth­ods, reduc­ing tox­ins and waste­water.

Olives con­tain phe­no­lic com­pounds that cre­ate a bit­ter fla­vor when they are fresh, and the com­pounds are often neu­tral­ized with chem­i­cals and repeated rinses, accord­ing to the paper, ​“Reducing phe­no­lics related to bit­ter­ness in table olives” by researchers Rebecca L. Johnson and Alyson E. Mitchell from the University of California, Davis. The paper was pub­lished in the Journal of Food Quality in August 2018.

“Current com­mer­cial table olive pro­cess­ing meth­ods remove many of these bit­ter phe­no­lic com­pounds and as a result, can alter the health-pro­mot­ing poten­tial of var­i­ous table olive prod­ucts,” the researchers wrote. ​“Additionally, cur­rent com­mer­cial table olive pro­cess­ing meth­ods are some of the most water-inten­sive meth­ods used in com­mer­cial food pro­cess­ing and can require more than 7,571 liters of water per ton of olives (e.g., California and Spanish meth­ods) and gen­er­ate highly toxic waste­water.”

The researchers wrote that their group exper­i­mented with four Amberlite resins and found that they not only removed the bit­ter­ness but saved the com­pounds for other uses rather than destroy­ing them.

“Preliminary results demon­strate that all resins could remove oleu­ropein dur­ing brine treat­ments thereby sig­nif­i­cantly reduc­ing olive bit­ter­ness with­out the need for addi­tional pro­cess­ing,” Johnson and Mitchell wrote.

Oleuropeins are only one phe­no­lic com­pound con­tained in olives, though they are the most com­mon dur­ing har­vest time, Johnson and Mitchell added.

There are three pri­mary meth­ods used by com­mer­cial olive proces­sors: Greek, Spanish and California. Johnson and Mitchell noted there are less pop­u­lar arte­sian means to deb­it­ter the olives, but added that they are not ideal for com­mer­cial use. The Greek style uses a smaller amount of water to the Spanish and California ones do, though each has its pros and cons. The California process uses the most water, accord­ing to the authors.

The prob­lem with waste­water from pro­cess­ing table olives has been noted before. In July 2018, Bárbara Rincón-Llorente, David de la Lama-Calvente, María J Fernández-Rodríguez, and Rafael Borja-Padilla wrote, ​“Table Olive Wastewater: Problem, Treatments and Future Strategy. A Review” pub­lished in Front Microbiol.

“At present, there is no stan­dard treat­ment for these waste­waters with accept­able results and which is applied in the indus­try,” they wrote. ​“Currently, the most com­mon treat­ment is the stor­age of these waste­waters in large evap­o­ra­tion ponds where, dur­ing the dry sea­son, the waste­water dis­ap­pears due to evap­o­ra­tion. This is not a solu­tion as the evap­o­ra­tion ponds depend com­pletely upon the cli­ma­tol­ogy and have a high num­ber of asso­ci­ated prob­lems, such as bad odors, insect pro­lif­er­a­tion and the con­t­a­m­i­na­tion of under­ground aquifers.”

In fact, olives are one of the worst foods as far as water use in the indus­try.

“Olive pro­cess­ing is one of the most water-inten­sive fruit or veg­etable pro­cess­ing meth­ods,” Johnson and Mitchell wrote. ​“The waste­water that is pro­duced is a dark efflu­ent with high organic bur­den and polyphe­nol con­tent that exhibits antibac­te­r­ial prop­er­ties. Releasing efflu­ent streams direct­ing into local water sys­tems or on land can result in tox­i­co­log­i­cal con­se­quences and envi­ron­men­tal con­t­a­m­i­na­tion.”

The water is gen­er­ally sent to evap­o­ra­tion ponds, which Johnson and Mitchell note has sev­eral prob­lems sim­i­lar to those noted in the ear­lier arti­cle pub­lished in Front Microbiol.

In both arti­cles, the researchers noted the crit­i­cal issue of pro­duc­ing large amounts of waste­water, par­tic­u­larly in regions that are already expe­ri­enc­ing drought.

The prob­lem has been com­pounded by higher demand for olives and olive oil.

“The con­sump­tion of table olives increased glob­ally by 182 per­cent, and olive oil con­sump­tion increased by 76 per­cent between 1990 and 2016,” Johnson and Mitchell wrote. ​“This increase is attrib­uted to the pop­u­lar­ity of the Mediterranean diet, which is linked to reduc­ing car­dio­vas­cu­lar dis­ease, Alzheimer’s dis­ease and other age-related con­di­tions.”

Johnson and Mitchell listed sev­eral dif­fer­ent poten­tial meth­ods of deb­it­ter­ing olives, not­ing that researchers have looked into using oxy­gen over­pres­sure, car­bon diox­ide over­pres­sure and more. The resin method both deb­it­tered the olives and pre­served the phe­no­lics for future use.

The authors rec­og­nized the impor­tance of local and time-hon­ored meth­ods but felt the need to look for less waste­ful ways to enjoy olives.

“Table olives are a pop­u­lar food prod­uct con­sumed world­wide,” Johnson and Mitchell wrote. ​“While tra­di­tional and region-spe­cific olive pro­cess­ing meth­ods should be cel­e­brated, there is the oppor­tu­nity to develop new tech­nolo­gies for deb­it­ter­ing olives, that will enable the cre­ation of novel prod­ucts with new tex­tures, fla­vors and health-pro­mot­ing prop­er­ties that will appeal to con­tem­po­rary con­sumers and expand mar­kets. Novel tech­nolo­gies can also reduce water and labor costs and increase envi­ron­men­tal sus­tain­abil­ity.”

• Journal of Food Quality


• Front Microbiol