Lactobacillus plantarum (widespread member of the genus Lactobacillus) is one of the most studied species extensively used in food industry as probiotic microorganism and/or microbial starter. The exploitation of Lb. plantarum strains with their long history in food fermentation forms an emerging field and design of added-value foods. Lb. plantarum strains were also used to produce new functional (traditional/novel) foods and beverages with improved nutritional and technological features. Lb. plantarum strains were identified from many traditional foods and characterized for their systematics and molecular taxonomy, enzyme systems (α-amylase, esterase, lipase, α-glucosidase, β-glucosidase, enolase, phosphoketolase, lactase dehydrogenase, etc.), and bioactive compounds (bacteriocin, dipeptides, and other preservative compounds). This review emphasizes that the Lb. plantarum strains with their probiotic properties can have great effects against harmful microflora (foodborne pathogens) to increase safety and shelf-life of fermented foods.

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Lactobacillus plantarum with Functional Properties: An Approach to Increase Safety and Shelf-Life of Fermented Foods.

Chemical constituents and health effects of sweet potato

Traditionally fermented pickles: How the microbial diversity associated with their nutritional and health benefits?

Summary
Tropical root and tuber crops [cassava, sweet potato, yams, colocasia (taro), etc] are important staples for food security for about a fifth of the world population. Bulk of cassava in Africa and Latin America are processed into fermented foods and food additives such as organic (acetic, citric and lactic) acids, mono-sodium glutamate, etc. The fermented foods from cassava are gari, fufu, lafun, chickwanghe, agbelima, attieke and kivunde in Africa, tape in Asia and ‘cheese’bread, and ‘coated peanut’ in Latin America. Lactic acid bacteria and yeasts are the major group of micro-organisms associated with cassava fermentation. Similarly, sweet potatoes can be fermented into soy sauce, vinegar, lacto-juices, lacto-pickles and sochu (an alcoholic drink produced in Japan), and yams into fermented flour. Most of these fermented food products are functional foods rich in phytochemicals, dietary fibres, anti-oxidant compounds (β-carotene, anthocyanin, etc) and probiotic components (lactic acid bacteria and yeasts).

Traditional and novel fermented foods and beverages from tropical root and tuber crops: review.

The review focuses on some of the high value-end biocommodities, such as fermented beverages, single-cell proteins, single-cell oils, biocolors, flavors, fragrances, polysaccharides, biopesticides, plant growth regulators, bioethanol, biogas and biohydrogen, developed from the microbial processing of fruit and vegetable wastes. Microbial detoxification of fruit and vegetable processing effluents is briefly described. The advances in genetic engineering of microorganisms for enhanced yield of the above-mentioned biocommodities are elucidated with selected examples. The bottleneck in commercialization, integrated approach for improved production, techno-economical feasibility and real-life uses of some of these biocommodities, as well as research gaps and future directions are discussed.

Microbial processing of fruit and vegetable wastes into potential biocommodities: a review.

Purple sweet potato (PSP) is a special type of sweet potato having high anthocyanin pigment in the root. The starch contents of PSP (root/water homogenised in 1:1 ratio) were enzymatically saccharified [using commercial thermostable enzymes TermamylÂ® (0.2%) and DextrozymeÂ®GA (1%)] to fermentable sugars, and the filtrate was ameliorated with cane sugar to achieve 20Â°âBrix, for subsequent fermentation into a red wine using 2% yeast (Saccharomyces cerevisiae) as starter culture. The wine had the following proximate compositions: total soluble sugar (TSS), 2.25Â°âBrix; starch, 0.15âg per 100âmL; total sugar, 1.35âg per 100âmL; TA, 1.34âgâtartaric acid per 100âmL; phenol, 0.36âg (caffeic acid equivalent) per 100âmL; anthocyanin, 55.09âmg per 100âmL; tannin, 0.64âmg per 100âmL; lactic acid, 1.14âmg per 100âmL; ethanol, 9.33%(v/v); and pH, 3.61. 2, 2âDiphenylâ1âpicrylhydrazyl (DPPH) scavenging activity of the wine was 58.95% at a dose of 250âI¼gâmLâ1. Principal component analysis reduced the eleven original analytical and proximate variables (TSS, starch, total sugar, TA, phenol, anthocyanin, tannin, lactic acid, ethanol, pH, DPPH) to four independent components, which accounted for 76.65% variations. Sensory evaluation was carried out by sixteen trained panellists on various attributes such as clarity, colour, viscosity, odour, flavour, spritz and finish. Independent âtâ test confirmed that all the sensory attributes of the PSP wine scored closely (within 10% variation) to that of a commercial grape wine. The red wine produced contains essential antioxidants and acceptable sensory qualities.

Proximate composition and sensory evaluation of anthocyanin-rich purple sweet potato (Ipomoea batatas L.) wine

Summary

Anthocyanin pigment-rich sweet potato (SP) cubes were pickled by lactic fermentation by brining the cut and blanched cubes in common salt (NaCl, 2–10%) solution. They were then inoculated with a strain of Lactobacillus plantarum (MTCC 1407) and incubated for 28 days. Treatment with 8–10% brine solution was found to be organoleptically most acceptable. The final product with 8% and 10% brine solutions had a pH (2.5–2.8), titratable acidity (TA) (1.5–1.7 g kg−1), lactic acid (LA) (1.0–1.3 g kg−1), starch (56–58 g kg−1) and anthocyanin content (390 mg kg−1) on fresh weight basis. Sensory evaluation rated the anthocyanin-rich SP lacto-pickle acceptable based on texture, taste, aroma, flavour and after taste. Principal component analyses reduced the eleven original analytical and proximate variables (pH, TA, LA, starch, total sugar, anthocyanin, organic mater, ash, fat, protein and calories) to three independent components (factors), which accounted for 91% of the total variations.

Anthocyanin‐rich sweet potato lacto‐pickle: production, nutritional and proximate composition

The success of any novel food product is largely determined by the consumer acceptance of its sensory quality. The objective of the present study was to evaluate the sensory attributes of lactic acid-fermented sweet potato (SP) pickles with the prospective consumers to develop a statistical model for predicting consumer acceptance decisions. The pickles prepared from β carotene- and anthocyanin-rich SP varieties in 8 and 10% salt (NaCl) solutions were evaluated for their sensory attributes, i.e., appearance, color, texture, aroma and sourness, by 100 rural consumers from the Orissa State of India during 2008. The consumers liked SP pickle made in 8% NaCl solution. The logistic regression modeling of the sensory and consumer attributes revealed that the sourness (Wald statistic = 11.328, P = 0.001) and aroma (Wald statistic = 8.374, P = 0.004) of the SP pickle determined the consumer acceptability. Analysis also showed that the highly educated consumers were most likely to accept this SP pickle (Wald statistic = 5.038, P = 0.025).



PRACTICAL APPLICATIONS

The rural people living in the geographically and socially isolated places of developing countries are often plagued by acute malnutrition. Fortifying the staple foods with essential nutrients is an effective strategy to eradicate malnutrition through natural means. Sweet potato (SP) is cultivated extensively in the rain-fed and hilly tracts of India and is a popular secondary staple food for tribes during off season. Vegetable pickles are popular adjuncts in India, which are consumed regularly along with staple foods. Thus, the pickles prepared from antioxidant-rich SP can provide essential nutrients like β-carotene and anthocyanin which can help the rural people to eradicate malnutrition at a cheaper cost. Besides, statistical modeling of the SP pickle acceptance decisions can help the policymakers to identify potential consumer segments for promoting this pickle.

Consumer acceptance of lactic acid-fermented sweet potato pickle

Greater yam (Dioscorea alata), a popular crop in India, is cultivated widely in Orissa state, India. In spite of the availability of several improved varieties, farmers preferred the local landraces. An investigation was carried out to identify whether the varietal preferences of yam farmers in two production systems, subsistence and commercial, were different. While the subsistence farmers demanded the yam varieties adaptable to a wide range of soils, the commercial farmers preferred the anthracnose-resistant cultivars. This study demonstrated that the farmers' varietal preferences were highly influenced by the production systems. Identifying the convergence/divergence of varietal preferences across production systems can help breeders to develop the high impact varieties.

P. Sethuraman Sivakumar

Papers

Proximate composition and sensory evaluation of anthocyanin-rich purple sweet potato (Ipomoea batatas L.) wine

Anthocyanin‐rich sweet potato lacto‐pickle: production, nutritional and proximate composition

Consumer acceptance of lactic acid-fermented sweet potato pickle

Production system-specific differences in farmers' demand for greater yam (Dioscorea alata) varietal attributes in Orissa State, India.