Research Article Received: 17 April 2014 Revised: 15 September 2014 Accepted article published: 19 September 2014 Published online in Wiley Online Library: (wileyonlinelibrary.com) DOI 10.1002/jsfa.6923 Use of the backslopping method for accelerated and nutritionally enriched idli fermentation Neha Shrivastava and Laxmi Ananthanarayan * Abstract BACKGROUND: Idli is a cereal–legume-based fermented food, widely consumed in India. It is popular for its nutritional content, sour taste and appetising aroma. The fermentation time of idli batter varies from 12 to 14 h. A reduction in fermentation time of idli batter is of great significance for large-scale idli production units since it will reduce the batch time and will lead to a greater output. Accelerated fermentation can be potentially achieved by using the backslopping method. The inoculum for backslopping was optimally fermented (12 h) idli batter, dried at room temperature. RESULTS: Backslopping reduced the fermentation time of idli batter from the conventional 12 h to 3 h while successfully maintaining sensory attributes of the product. In the idlis prepared by backslopped expedited batter, thiamine was found to be 50% higher; while reduction of anti-nutrients phytate (11%) and trypsin inhibitor (16%) was higher than the conventionally fermented (12 h) idli batter. CONCLUSION: Backslopping not only accelerated idli batter fermentation but also enhanced its nutritional value. A similar process can be designed for other fermented foods, to expedite fermentation thus reducing the time requirement. © 2014 Society of Chemical Industry Keywords: idli; backslopping; inocula; dehydration; thiamine; anti-nutrients INTRODUCTION Idli is a popular food product prepared from an auto-fermented batter of rice (Oryza sativa L.) and black gram [Vigna mungo (L.) Hepper; synonym Phaseolus mungo L.] dahl (split dehulled beans) usually taken in a proportion of 3:1. 1 Initially, idli originated in south India but recently has gained popularity throughout India and is now a part of global cuisine due to its soft spongy tex- ture, characteristic sour taste, and an attractive aroma. Apart from its organoleptic properties, it is highly nutritive and a significant source of calories, proteins and micronutrients. Fermentation of the batter causes an increase in the protein efficiency ratio, essen- tial amino acids and vitamins such as niacin, riboflavin and thi- amine, together with a decrease in anti-nutrient content, over the unfermented counterpart. 2 – 4 The total time required for its preparation is about 15–18 h including washing, soaking, grind- ing, fermenting and steaming, thus making it a time consuming and energy intensive process especially when applied at an indus- trial scale. The earliest production of fermented foods was based on spon- taneous fermentation, where the quality of the end product was dependent on the microbial load and spectrum of raw mate- rial. Gradually, spontaneous fermentation was optimised through backslopping, which is the inoculation of the raw material with a small quantity of a substrate from a previous successful fermented batch. Although not a microbiologically characterised method, it can bring about an expedition in the fermentation due to a greater microbial load. Backslopping is beneficial in reducing fer- mentation time and makes the fermentation predictable. 5 There are some reports regarding fermented foods where backslopping is used. 6 Backslopping inoculum has been previously suggested for sourdough fermentations. 7 Nout et al. 8 carried out acceleration in the fermentation of kenkey from 3–4 days to 12–14h by the use of starter dough. Incwancwa, a South African non-alcoholic fermented beverage, is prepared by fermenting the maize meal over a 1- to 3-day period using spontaneous fermentation by lactic acid bacteria (LAB) originating from maize. Chelule et al. 9 have sug- gested that the future fermentation of Incwancwa can be carried out by backslopping, using the previously fermented maize meal as a source of inoculum. Some cheese-making processes entail the use of backslopping to process farmhouse goat cheeses (Roca- madour, Picodon), Swiss-type cheeses and hard cheeses (Parmi- giano Reggiano, Comté, Sbrinz). 10 Inocula for backslopping may be preserved by dehydration (air/sun drying) and grinding into powder, which enhances the viability of the microorganisms over relatively long periods. Also, various carriers such as porous material of gourd have been used to achieve backslopping, e.g. in Ghana ‘inoculation belt’ is used for the initiation of pito beer fermentation. In Egypt khisk is ∗ Correspondence to: Laxmi Ananthanarayan, Food Engineering & Technol- ogy Department, Institute of Chemical Technology, Nathalal Parekh Marg, Matunga, Mumbai – 400019, Maharashtra, India. E-mail: laxmi.ananth.iyer@gmail.com Food Engineering & Technology Department, Institute of Chemical Technology, Nathalal Parekh Marg, Matunga, Mumbai 400019, Maharashtra, India J Sci Food Agric (2014) www.soci.org © 2014 Society of Chemical Industry