Effect of pH on the chemical stability of carotenoids in juice

Abstract

Carotenoids are abundantly present in fruits and vegetables and are considered beneficial for human health. Although carotenoids are inherently unstable and degradation occurs during food preparation and storage, bioavailability of β-carotene from processed foods, such as carrot juice, can be up to 70 % higher as from raw carrots (1) . Thus, well-chosen food processing techniques can increase health benefits of fruit and vegetables. During juice and smoothie preparation, organic acids are released from sheered plant cells (2) . Carotenoids are sensitive to environmental factors such as light, temperature, oxygen as well to acidic conditions (3) . This study investigated the effect of pH on carotenoid stability in juice.Freshly prepared carrot juice (pH 6·07) was adjusted to pH 8, 7, 6, 5, 4 and 3 using citric acid or NaOH and stored at 4°C for 4 days. Juice samples were freeze-dried and total carotenoids extracted and quantified as previously described (4) . Neutral and slightly basic conditions (pH 8 and 7) reduced total carotenoid content by 26 % (p < 0·05) and acidic conditions (pH 6, 5, 4 and 3) increased the measured total carotenoid content in carrot juice by 18 %, 22 %, 27 % and 22 % respectively (p < 0·05) (Figure 1).When fresh fruit and vegetable juices (carrot, lemon, orange and apple) were blended to attain a pH of 3·15, 3·98 and 4·95, no carotenoid degradation was observed after 8 day storage at 4°C. A pH of 3·15 however resulted in a 16 % reduction of total carotenoids (p < 0·05) (Figure 2).These findings indicate that carotenoids in fresh juices were sensitive to pH. However, observed carotenoid degradation in fruit and vegetable juice was small (16-25 %). The apparent increase of total carotenoid content (∼20 %) in acidified carrot juice may be due to enhanced solubility of crystallized carotenoids present in the vacuoles of plant material (5) . While our findings confirm the notion that carotenoids are pH sensitive all observed variation were less than 25 %.

The Influence of Temperature, Storage Conditions, pH, and Ionic Strength on the Antioxidant Activity and Color Parameters of Rowan Berry Extracts

“…These changes resulted in increased chromaticity (C*) and significant color differences (∆E) compared to controls. Such color modifications are caused by the degradations of carotenoids, but also polyphenols, widely reported by other authors [33,34]. Table 5 presents the color parameters after adding different salts to the extract.…”

Changes in color and carotenoids of sweet corn juice during high‐temperature heating

“…Kinetic modeling is a useful tool to predict the affection of thermal process on carotenoids degradation. Meanwhile, in acidic juice system, organic acids are released from sheered plant cells during juice preparation, carotenoids should be impacted by those acidic conditions (Bell, Alamzad, & Graf, 2016). Also, some studies evaluated the degradation kinetics of carotenoids from dehydrated apricot (Fratianni et al, 2013), carrot (Koca et al, 2007), and pumpkin (Song, Wang, Li, Meng, & Liu, 2017).…”

“…Most solid food materials can be regarded as capillary-porous models, while liquid materials are nonporous models. Meanwhile, in acidic juice system, organic acids are released from sheered plant cells during juice preparation, carotenoids should be impacted by those acidic conditions (Bell, Alamzad, & Graf, 2016). Up to now, as a neutral cereal juice, the degree of degradation of carotenoids in sweet corn juice as affected by various heating treatments remains uncertain.…”

Effects of pH, High Pressure Processing, and Ultraviolet Light on Carotenoids, Chlorophylls, and Anthocyanins of Fresh Fruit and Vegetable Juices

“…Meanwhile, fresh blended juices of carrot, lemon, orange, and apple with low pH (3.15, 3.98 and 4.95) showed no reduction of carotenoid after 8 days of storage at 4°C. However, at the lowest pH (3.15), 16% decrease of total carotenoids occurred [64]. These findings show that, despite the degradation of carotenoids in fruit and vegetable juices was considerably low (<25%), in acidic condition the total carotenoid content tended to increase which may be caused by the enhancement in the solubility of crystallized carotenoids available in the vacuoles of plant material [65].…”

“…Furthermore, starfruit juice provided hue value 120° while mango juice was 109° which both reduced to 89° and 80°, respectively, when the pH increased, indicating the change of color [63]. In addition, freshly prepared carrot juice with pH 6.07 and was adjusted to pH 3-8 resulted in the reduction of total carotenoid by 26% at neutral and A B C slightly basic condition (pH 7 and 8) and an increase in the total carotenoid by 22%, 27%, 22%, and 18% at pH 3-6, respectively [64]. Meanwhile, fresh blended juices of carrot, lemon, orange, and apple with low pH (3.15, 3.98 and 4.95) showed no reduction of carotenoid after 8 days of storage at 4°C.…”