Natural Acidification with Low-pH Fruits and Incorporation of Essential Oil Constituents for Organic Preservation of Unpasteurized Juices.

Unlabelled: Essential oil constituents (EOCs) derived from antimicrobial plant extracts can be used for organic preservation of food products. However, the characteristic flavor resulting from EOCs limit the concentration that can be used in high-pH beverages. This work provides an innovative approach of organically preserving a high-pH beverage (watermelon juice) with a natural blend of low-pH fruits (apples and lemons) and EOCs simultaneously. This low-pH fruit blend not only lowers the pH of the food to below critical pH (4.6), but also reduces the potential off-flavors of EOCs, offering a good preservation approach. This was verified using a sensory trial (n = 50) coupled with storage studies and evaluation of various quality parameters using an extreme vertices mixture design with varying proportions of the fruit-base (watermelon juice), the acidulant (apple-lemon juice blend), and the antimicrobial agent (EOC blend). EOC and acidulant containing juices received better sensory scores than those without acidulant, but lower than when EOCs were absent. Microbial load of juices with EOCs after 14 days of storage did not deviate from day 0, while those without EOCs increased 3-fold on a logarithmic scale. Juices containing EOCs also had higher total phenolic content and antioxidant capacity. However, presence of EOCs did not impact pH, total soluble solids, titratable acidity or color, while acidification had significant effects on pH and titratable acidity. Optimum composition of juice formulations were prescribed according to a multi-parameter optimization algorithm. We concluded that the process of natural acidification (with apple-lemon juice blend) coupled with antimicrobial plant extracts is successful in extending the shelf-life of fruit juices with minimal effects on quality/sensory parameters.

Practical Application: This research proposes using a unique method for organic preservation of juices using very small amounts of essential oil constituents and acidification. Off-flavors that may arise can be mitigated without the use of chemical additives, but rather with a blend of tart fruit juices, such as apple and lemon juices. The EOCs and the acidulant act synergistically as a hurdle to inhibit microbial growth, so that thermal processing does not need to be employed.