**1. Introduction**

Tomato (*Solanum lycopersicum*), touted to be the most important vegetable crop, is consumed both in its fresh and processed forms. Its production in India amounted to 21.18 million metric tons in 2021 [1]. Tomato processing generates 1.5 to 5% pomace, which is a waste product but is a storehouse of nutrition [2,3]. It is used as animal feed or is dumped in landfills [4], thus having both economic and environmental implications since additional costs for transportation are required. Therefore, recycling and reusing pomace can reduce tomato processing costs [5].

Majority of the world population consumes wheat in one form or the other but in recent years, increasing number of people are showing sensitivity towards the gluten present in wheat, rye, and barley, which causes health problems for them [6]. The symptoms include fatigue, weight loss, diarrhea, and depression [7]. Since there is no cure ye<sup>t</sup> for celiac disease, the only option is to have a gluten-free diet. Any food that contains less than 20 ppm (or 20 mg/kg) of gluten is defined by United States Food and Drug Administration (FDA) as gluten free [8]. Furthermore, not all consumers who prefer gluten-free food have celiac disease. Many switch to it as a matter of personal preference, to meet specific dietary requirements, as fasting food, or just to have healthy food [9,10]. Additionally, there is a change in eating patterns and individual preferences, and experimentative palates have resulted in the creation of new markets for ready-to-cook foods that effectively reduce

**Citation:** Rehal, J.K.; Aggarwal, P.; Dhaliwal, I.; Sharma, M.; Kaushik, P. A Tomato Pomace Enriched Gluten-Free Ready-to-Cook Snack's Nutritional Profile, Quality, and Shelf Life Evaluation. *Horticulturae* **2022**, *8*, 403. https://doi.org/10.3390/ horticulturae8050403

Academic Editors: Dasha Mihaylova and Aneta Popova

Received: 30 March 2022 Accepted: 2 May 2022 Published: 3 May 2022

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**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

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drudgery, cooking time, and procurement of multiple ingredients while adding convenience and variety to the meal [11]. Consumers perceive readymade frozen foods as nourishing, healthy, and delicious [12]. In this scenario, snacks have now become an important part of any diet and biting into a healthy snack serves both the purposes of convenience and nutrition. Besides being gluten-free, the snack should serve the dual purpose of being able to be indulged in as well as provide nutrition for wider acceptance. However, the availability of convenient gluten-free traditional snacks is very limited in the Indian market, and even if available, these are expensive [13].

Finger millet (*Eleusine coracana* L.) is the most consumed small millet in India and accounts for 85% of all millet produced in India [14]. It has an excellent nutritional profile compared to commonly consumed cereals [15–17]. Its crude fiber and mineral contents are markedly higher than those of wheat (1.2% fiber and 1.5% minerals) and rice (0.2% fiber and 0.6% minerals); its protein is relatively better balanced; and it contains more lysine, threonine, and valine than other millet. It has the highest calcium content among all cereals (344 mg/100 g), which is almost three times more than milk and tenfold higher than brown rice, wheat, or maize [17]. The total dietary fiber content of finger millet grain (19.1%) is reported to be the highest compared to that of many other cereal grains (12.1%, 3.7%, 12.8%, and 11.8%, respectively, for wheat, rice, maize, and sorghum) [16].

Despite the ample availability of tomato pomace as well as a healthy gluten-free alternative grain, there are not many products on the market to meet the demand for convenient gluten-free snacks due to the lack of optimized methods for their preparation. The utilization of tomato pomace in food products is challenging, owing to its highly perishable nature, acidity, and the lack of knowledge of how it affects the quality attributes of the prepared product.

The present study was hence undertaken with the purpose of developing a ready-tocook gluten-free (RTC-GF) snack using finger millet and tomato pomace that has good acceptability and palatability and to study the nutritional traits and shelf-life of the product.

### **2. Materials and Methods**

Fresh tomato pomace (variety: *Punjab Ratta*), devoid of any foul odor or taste, was obtained from the Food Industry and Business Incubation Centre, Punjab Agricultural University, Ludhiana. Immediately after procurement, it was dried in a tray dryer at 50 ◦C for 48 h and then milled in the mixer grinder (Inalsa Inox 1000 model) and sieved through 40 mm sieve to ge<sup>t</sup> a fine tomato pomace powder (TPP). The powder was packed in polyethylene bags and stored in a refrigerator at 4 ± 2 ◦C till further use.

More than 1500 germ plasm lines of finger millet were acquired by PAU, Ludhiana from NBPGR, New Delhi, due to the feasibility of its profitable cultivation in Punjab. After initial screening, a high yielding, stable, and promising line, IC0475677, was shortlisted for further testing. Seeds from this line were procured from the university's Department of Plant Breeding and Genetics, thoroughly cleaned and washed, and then dried at 60 ± 2 ◦C for 6 h in a tray dryer. They were milled to ge<sup>t</sup> finger millet flour (FMF) using a Laboratory Mill 3303 (Perten Instruments), sieved through a 40 mm sieve, packed in polyethylene bags and stored in a refrigerator at 4 ± 2 ◦C till further use.

Potato flour (PF) was prepared by the standard procedure, where the potatoes are washed, peeled, diced, boiled, dried in a cabinet drier at 50 ◦C, ground, sieved, and packed in airtight containers [18]. Fresh ginger, garlic, green chilies, and coriander, along with salt, spices, and refined soybean oil, were procured from the local market.
