Effects of Lactic Acid Fermentation on the Retention of Β-Carotene Content in Orange Fleshed Sweet Potatoes

Abstract

This study aimed to establish the effects of lactic fermentation on the levels of β-carotene in selected orange fleshed sweet potato (OFSP) varieties from Kenya. Furthermore,it sought to demonstrate fermentation as a potential process for making new products from sweet potato with enhanced nutraceutical attributes. The varieties (Zapallo, Nyathiodiewo and SPK004/06) were fermented with Lactobacillus plantarum MTCC 1407 at 25 ± 2ºC for 48 h and kept for 28 days to make lacto-pickles. During fermentation both analytical (pH, titratable acidity (TA), lactic acid (LA), starch, total sugar, reducing sugar (g/kg roots), texture (N/m 2 ), β-carotene (mg/kg roots)) and sensory (texture, taste, flavour and after taste) attributes of sweet potato lacto-juice were evaluated. Process conditions were optimized by varying brine levels, with fermentation time. A UV-visible spectrophotometer was used to identify and quantify β-carotene. Any significant variations (p < 0.05) in analytical attributes between the fermented and unfermented samples (pH, LA, TA and β-carotene concentration) of lacto-pickles, prepared from the potato roots, were assessed. The study reported a final composition of 156.49mg/kg, 0.53mg/kg, 0.3N/m 2 , 1.3g/kg, 5.86g/kg, 0.5g/kg and 5.86g/kg for β-carotene, Ascorbic acid, texture; Starch, total sugars, LA and TA respectively, and a pH of 3.27. The fermented products were subjected to flavour profiling by a panel. The product sensory scores were 1.5 to 2.5 on a 5 point hedonic scale, ranging from dislike slightly to like much. The products with brine levels at 4 and 6% were most preferred. The retention of β-carotene was 93.97%. This demonstrated lactic acid fermentation as a better method for processing OFSP as the main nutritional attributes are retained. The final product was resistant to spoilage microorganisms after 28 days of fermentation. Further preservation could be obtained by addition of sodium metabisulphite. In conclusion, Lactic acid fermentation using L. plantarum is a novel method of producing Lacto pickles from Zapallo OFSP, with 93.97% β-carotene retention and adequate shelf life.

The Effect of Sodium Total Substitution on the Quality Characteristics of Green Pickled Tomatoes (Solanum lycopersicum L.)

“…It seems that the NaCl addition had a positive effect on the β -carotene retention in green pickled tomatoes during the fermentation period. These findings are similar to Reference [ 33 ] for 10 vegetables and Reference [ 34 ] for orange fleshed sweet potato, which have reported the improvement of the levels of bioactive compounds and antioxidant capacities of pickled vegetables after 30 days of fermentation. Depending on the type of salt, this could help dissociate the carotenoid protein complexes into the brine or maintain them in the pickles.…”

Effect of Natural Fermentation on the Chemical Composition, Mineral Content, Phytochemical Compounds, and Antioxidant Activity of Ziziphus spina-christi (L.) “Nabag” Seeds

“…The fermentation of seeds for 48 h resulted in the highest total carotenoid content of 14.0 mg/g compared to 6.5 mg/g for unfermented "Nabag" seeds. This finding agrees with that of Oloo et al [39], who reported a significant increase in the carotenoid content of orange flash potato fermented for 2 days. Similarly, Ortiz et al [40] observed that the fermentation of bio-fortified maize for 24 and 72 h resulted in a 100% increase of pro-vitamin A carotenoid, while prolonging the fermentation time to 120 h or more reduced the carotenoid content of maize.…”

Fermentation Affects the Antioxidant Activity of Plant-Based Food Material through the Release and Production of Bioactive Components

“…Fermentation can increase the release of carotenoids [ 55 ]. For example, lactic acid fermentation can preserve β-carotene more than other processing techniques, such as deep-frying, blanching, and drying [ 56 ]. In addition, Lactobacillus plantarum (29DAN, 83DAN) was able to increase the carotenoid content in wheat dough due to the higher solubility of these antioxidant compounds [ 50 ].…”