Effects of Cooking Techniques on the Nutritional Profile, Glycemic Index, and Sensory Evaluation of Rice: A Systematic Review

Abstract

The consumption of white rice－an important component of diets in many regions, especially in Asia－has been linked to an increased risk of type 2 diabetes mellitus (T2DM). The high glycemic index (GI) of white rice results in a rapid increase in postprandial glucose levels. However, the particular variety and cooking method used considerably impact the glycemic impact of white rice. Particularly, short-grain and glutinous rice varieties, characterized by higher amylopectin-to-amylose ratios, tend to have higher GIs than long-grain varieties. This investigation explored the impact of different cooking techniques on the nutritional composition, GI, and sensory characteristics of rice. A thorough evaluation was conducted through a systematic review of the existing literature, employing databases such as Science Direct, PubMed, Google Scholar, Garuda, IPB Repository, and Brawijaya University Repository, with peer-reviewed articles, conference papers, and other reliable sources being analyzed. The findings reveal complex interactions among rice varieties, cooking methods, and their effects on the GI, nutritional profile, and sensory evaluation of rice. Parboiling and postcooking cooling proved effective for reducing the glycemic response in healthy subjects. However, a critical limitation of the present work is the complete absence of studies involving diabetic patients, despite our focus on T2DM risk reduction. Although our findings provide mechanistic evidence for the formulation of clinical recommendations, randomized controlled trials in diabetic populations must be conducted before clinical recommendations can be established.

INTRODUCTION

High consumption of white rice has been associated with an increased risk of type 2 diabetes mellitus (T2DM) in various populations. The high carbohydrate content of white rice－a major source of carbohydrates in many countries, particularly in Asia－contributes to this increased risk. Previous studies have established an association between a higher intake of white rice and increased T2DM risk, especially in Asian populations such as Chinese and Japanese women (Villegas et al., 2007; Hu et al., 2012). A meta-analysis by Hu et al. (2012) revealed that the consumption of approximately 158 g of white rice daily may increase the risk of T2DM by approximately 11%. In addition, increased consumption of processed grains, such as white rice, has been associated with increased metabolic risk in Indian and Japanese populations (Murakami et al., 2006; Radhika et al., 2009). These findings indicate that dietary patterns and carbohydrate intake must be considered to prevent and manage T2DM.

White rice has a high glycemic index (GI), generally falling between 70 and 80 for short-grain types and 50－60 for long-grain types (Kaur et al., 2016). When consumed, easily accessible starch in rice rapidly breaks down into glucose, resulting in a rapid and notable elevation of blood glucose levels. Factors such as rice variety, amylose and amylopectin contents, and the employed processing method (determining starch gelatinization and particle size) also affect the GI of rice (Rimbawan and Siagian, 2004; Rimbawan and Nurbayani, 2013). Studies have shown that rice with a high-amylose content tends to have a lower GI than rice with a low amylose content (Indrasari et al., 2008). This is corroborated by the findings that Rojolele white rice, which is high in amylose, tends to produce a lower glycemic response (Rimbawan and Siagian, 2004; Thamrin et al., 2023). Overall, higher fiber content, amylose content, and amylose/amylopectin ratio are associated with lower glycemic response and GI (Nurhayati et al., 2019). In addition, amylose contributes to the aroma and flavor of rice (Rosanti et al., 2023).

The physical and chemical properties of rice, such as texture, moisture content, and gelatinization, are determined by the rice variety and cooking method and considerably affect the sensory characteristics and GI of cooked rice. For example, the extent of starch gelatinization during cooking can impact the texture and viscosity of cooked rice, with higher gelatinization levels making rice softer and more digestible (Taghinezhad et al., 2016). Moreover, the moisture content of rice, which may vary based on storage conditions and cooking method, is a key factor determining the ultimate texture and taste of the cooked grain (Ding et al., 2019). These elements collectively contribute to the observed variations in sensory experiences and glycemic responses associated with different types of cooked rice.

The processing and cooking techniques greatly affect the GI of rice, which quantifies the rate at which blood sugar levels increase after consumption. Research on several rice varieties revealed that traditional cooking techniques involving boiling yielded a GI of 21.6, which increased to 24.7 after holding the rice at room temperature for 12 h (Purbowati and Kumalasari, 2023). At the same time, rice boiled in a rice cooker had a GI of 22.9, which increased to 36.4 after storage at a high temperature in a rice cooker for 12 h. These variations underscore the need to consider specific cooking processes when assessing the health effects of rice consumption, especially for people who manage their blood sugar levels (Taghinezhad et al., 2016).

Cooking method considerably affects the nutritional profile, GI, and sensory properties of rice, warranting a comparative analysis of different cooking methods. This comparison is particularly important given that rice is a major contributor to the glycemic load for billions of people and its association with an increased risk of T2DM and other chronic diseases (Hu et al., 2012).

The elucidation of the effects of different cooking methods on the physicochemical properties, GI, and sensory evaluation of rice is expected to benefit consumers and inform food scientists and dieticians in choosing cooking techniques that produce the greatest health benefits. Additionally, the elucidation of the relationship between white rice consumption, GI, and T2DM risk may help individuals make healthier food choices and reduce their risk of developing T2DM. However, it is important to note that most available research on cooking methods and glycemic responses has been conducted in healthy populations, with the clinical data for diabetic patients being scarce. This constitutes a substantial gap in translating mechanistic findings to clinical practice for diabetes management.

This systematic review critically analyzes and comprehensively investigates the literature published until 2024. We thoroughly examined how various cooking techniques can modify the nutritional profile, GI, and sensory characteristics of rice. The results of this study are expected to help consumers and healthcare practitioners make well-informed decisions that align with their health objectives and culinary tastes, contributing to the broader discussion on nutrition and public health.

Therefore, the primary objective of this systematic review was to comprehensively analyze the existing literature and compile the current knowledge on how various cooking techniques affect the nutritional composition, GI, and sensory evaluation of rice. This systematic review is necessary because: (1) scattered research findings across different studies make it difficult for consumers and healthcare providers to make evidence-based recommendations; (2) no comprehensive synthesis has been conducted to compare traditional and modern cooking methods; and (3) elucidation of these relationships may provide mechanistic insights that could inform future clinical research on dietary strategies for rice-consuming populations, although clinical validation in diabetic patients remains essential.

MATERIALS AND METHODS

Data extraction

This systematic review followed established PRISMA guidelines (Fig. 1) and employed a comprehensive search strategy across multiple electronic databases to identify the relevant literature on the effects of cooking methods on the nutritional and sensory properties of rice. The search was done in four major international databases: Google Scholar, PubMed, Science Direct, and Garuda (Indonesia’s national research repository). To capture both global perspectives and regional cooking practices, the search strategy incorporated domestic university repositories from Indonesian institutions, specifically IPB University and Brawijaya University repositories, which house commendable collections of rice-related research because Indonesia is a major rice-consuming country.

Fig. 1.

Flow chart of the article selection process. Literature identification and screening workflow followed the PRISMA methodology.

The search strategy utilized a carefully constructed combination of keywords designed to capture the full spectrum of research on rice cooking: “modern cooking techniques of rice,” “electric rice cooker,” “traditional cooking techniques of rice,” “physicochemical characteristics of rice,” “glycemic index of rice,” “sensory evaluation of rice,” and “sensory assessment of rice.” These terms were selected based on preliminary searches and expert guidance to ensure comprehensive coverage of studies examining the impact of various cooking methods on rice properties. The search parameters were restricted to publications in English and Indonesian between 2000 and 2024 to balance comprehensiveness with contemporary relevance while including considerable contributions of regional studies.

Study selection and screening process

The initial database search generated 156 records distributed across the selected repositories: 61 from Science Direct, 44 from PubMed, 32 from Google Scholar, 8 from the Garuda database, 7 from the IPB Repository, and 4 from the Brawijaya University Repository. No additional records were identified through the systematic scanning of reference lists or gray literature sources.

Following the PRISMA guidelines, 17 duplicate records were removed, leaving 139 unique studies for screening. During the initial screening phase, titles and abstracts were reviewed, and 75 records were excluded because they did not meet the inclusion criteria. This left 64 reports that appeared sufficiently promising for full retrieval.

Unfortunately, 11 of those reports could not be accessed because of access limitations. Specifically, 9 articles were behind paywalls without institutional access from publishers such as Elsevier, Springer, and Wiley, where university library subscriptions did not provide access to these specific publications; and 2 were conference proceedings that appeared in database searches but were only available as abstracts in the conference records, with full papers not published or archived in accessible formats. Despite attempts to directly contact the authors for copies of their work, these materials remained inaccessible within the timeframe of this review. Consequently, 53 full-text articles were available for evaluation.

In the final eligibility assessment, another 31 reports were excluded because 19 of them contained duplicate data from previous publications by the same research groups, 5 did not have sufficient outcome data for analysis, and 7 had study designs not relevant to the current research questions. As a result, 22 studies were used in the present review (Fig. 1).

Quality assessment

The inclusion criteria were straightforward but thorough. Studies were included if they met the following requirements: (1) peer-reviewed studies published in English or Indonesian between 2000 and 2024; (2) studies that examined how different cooking methods affect the characteristics of cooked rice; (3) research that measured at least one relevant outcome (nutritional composition, GI, or sensory evaluation); (4) studies that used solid quantitative measurement methods; and (5) both experimental and observational study designs.

Clear exclusion criteria were also established to ensure that the review is focused and methodologically sound. Studies were excluded if they were (1) review articles, editorials, and conference abstracts without full text; (2) studies that only examined rice varieties without comparing cooking methods; (3) research that only looked at the properties of raw rice; (4) studies that did not provide sufficient methodological detail for quality evaluation; (5) duplicate publications from the same research group using identical data; and (6) studies focused on rice-based products such as rice noodles or rice cakes rather than plain cooked rice.

This systematic approach ensured that the final set of studies was both relevant to the research questions and sufficiently methodologically rigorous to draw meaningful conclusions.

RESULTS AND DISCUSSION

The comprehensive analysis presented herein provides valuable insights for food scientists, nutritionists, and researchers considering rice preparation techniques and their effects on nutritional properties. The findings reveal that the cooking method substantially affects the nutritional outcome, glycemic response, and sensory evaluation in healthy populations. However, a critical limitation emerged: all the reviewed studies examined only healthy subjects and provided no clinical data for diabetic patients.

The analysis of 22 studies revealed fascinating patterns about how different cooking methods transform rice at the molecular and functional levels. The evidence demonstrated that the cooking method affects not only the taste or texture of rice but also fundamentally alters the nutritional value, glycemic response, and even the antioxidant capacity of rice, which has important implications for food product development.

This systematic review uncovered remarkable diversity in how different cultures prepare rice, with each method producing distinct nutritional profiles. Traditional techniques passed down through generations often prove superior to modern conveniences in preserving nutrients and managing glycemic impact. Fig. 2 exhibits these complex relationships between the cooking methods and rice properties.

Fig. 2.

Effects of cooking methods on the nutrient content and functional properties of rice. GI, glycemic index; GAE, gallic acid equivalent; DPPH, 2,2-diphenyl-1-picrylhydrazyl; TAE, tannic acid equivalent.

The effect of cooking method on nutrition profile of rice

The nutritional profile of rice is considerably affected by the employed cooking method. The relationship between preparation techniques and nutritional outcomes is dynamic, and its elucidation is of considerable interest to both nutrition experts and health-conscious consumers.

Macronutrient content

The cooking method does not considerably affect the protein content of rice but can change the bioavailability and digestibility of rice proteins. The data in Table 1 indicate substantial variation in the protein content, ranging from approximately 3% to 13% across different rice varieties and cooking methods. Notably, the pressure-cooked rice varieties examined by Meera et al. (2019) exhibit exceptionally high protein contents－12.64%, 11.81%, and 13.20% for the Kattuyanam, Red Kavuni, and Black Kavuni varieties, respectively－suggesting that pressure cooking may enhance protein retention compared with other methods. In contrast, rice prepared using an electric rice cooker generally shows lower protein content than both raw rice and traditionally cooked varieties. Trinidad et al. (2013) reported protein concentrations ranging from 3.10% to 5.00% for various rice varieties prepared in a rice cooker; these values are consistently below those typically observed in raw rice. This reduction was attributed to protein denaturation and leaching occurring during extended cooking in electric rice cookers.

Table 1.

Nutritional composition of cooked rice depending on rice variety and cooking method¹⁾

Reference	Country	Rice variety	Cooking method	Ash (g/100 g)	Moisture (g/100 g)	Protein (g/100 g)	Fat (g/100 g)	Carbohydrate (g/100 g)	Dietary fiber (g/100 g)
Traditional preprocessing methods: parboiling studies
Widowati et al. (2009)	Indonesia	Sintanur	Parboiled	0.85	11.99	7.30	0.90	78.96	10.05
		Gilirang	Parboiled	0.66	11.60	6.60	0.78	80.36	9.24
		IR 64	Parboiled	0.56	11.82	7.58	0.77	79.27	8.71
		Mekongga	Parboiled	0.63	11.23	7.59	0.56	79.99	10.27
		Ciherang	Parboiled	0.56	11.43	7.08	0.78	80.15	8.19
		IR 42 (white rice)	Parboiled	0.84	11.65	6.98	1.20	79.33	9.25
		Batang Lembang	Parboiled	0.75	11.51	7.52	1.01	79.21	8.52
Tresnandiati et al. (2019)	Indonesia	Adan (black rice)	Parboiled	0.41	60.022)	4.88	0.43	34.26	3.76
Traditional cooking methods: boiling
Fatema et al. (2010)	Bangladesh	BR-14	Boiled	1.22	12.77	7.50	1.97	76.54	1.00
		BR-29	Boiled	1.07	13.45	7.00	2.35	76.13	1.10
		BR-44	Boiled	1.01	11.20	8.80	1.75	77.24	1.00
Arachchilage and Ekanayake (2024)	Sri Lanka	Pokkali	Boiled	1.20	60.302)	9.30	4.60	24.60	6.40
		Marugakayan	Boiled	1.40	66.002)	6.90	4.10	21.60	5.40
		Rathdel	Boiled	1.50	64.802)	8.50	4.40	20.80	7.50
		Madathawalu	Boiled	1.50	62.202)	7.80	4.30	24.70	8.60
		Kuruluthuda	Boiled	1.40	61.902)	8.70	5.10	20.80	9.00
		Pachchaperumal	Boiled	1.50	61.802)	8.20	4.20	22.10	8.40
		Suduheenati	Boiled	1.50	67.702)	9.20	5.50	16.60	6.40
		Suwadel	Boiled	1.60	55.902)	9.50	5.50	27.40	7.40
		Kaluheenati	Boiled	1.40	70.502)	8.50	4.50	15.60	7.20
		Mavee	Boiled	1.30	65.202)	9.20	4.90	20.40	6.80
		Masuran	Boiled	1.50	70.602)	7.40	6.00	20.40	5.40
		Gonabaru	Boiled	1.10	66.302)	5.90	4.40	22.20	7.40
		Kahawanu	Boiled	1.50	67.402)	8.20	4.70	18.40	5.90
		Kahamala	Boiled	1.70	65.602)	4.80	5.20	22.70	6.40
		Hetadawee	Boiled	1.60	62.402)	7.20	5.40	24.40	6.00
		Behetheenati	Boiled	2.00	63.902)	7.40	5.30	20.40	6.70
Traditional cooking methods: steaming
Tresnandiati et al. (2019)		Adan (black rice)	Steamed	0.44	65.212)	5.52	0.75	28.08	5.22
Modern cooking methods: rice cooker
Erico et al. (2018)	Indonesia	Mayang Pandan MD 0%	Rice cooker	1.61	12.58	9.84	3.69	72.28	7.54
		Mayang Pandan MD 80%	Rice cooker	0.90	13.20	9.48	1.99	74.43	6.95
Syadiah and Rimbawan (2010)	Indonesia	Ciherang	Rice cooker	0.11	65.452)	4.82	0.17	29.45	2.21
Trinidad et al. (2013)	Philipines	IMS 2	Rice cooker	0.50	52.502)	5.00	0.80	41.20	2.10
		Sinandomeng	Rice cooker	0.20	55.902)	3.60	0.50	39.80	0.90
		NSIC Rc160	Rice cooker	0.20	57.302)	3.60	0.40	38.50	1.60
		PSB Rc18	Rice cooker	0.20	57.602)	3.10	0.60	38.50	0.90
		IR 64 (white rice)	Rice cooker	0.20	58.902)	3.50	0.40	37.00	1.60
		PSB Rc12	Rice cooker	0.10	61.802)	3.20	0.40	34.50	1.60
		PSB Rc10	Rice cooker	0.20	62.702)	3.10	0.40	33.60	1.60
		Sinandomeng (brown rice)	Rice cooker	0.80	57.602)	3.50	1.40	36.70	5.00
		IR 64 (brown rice)	Rice cooker	0.80	57.602)	3.70	1.50	36.40	5.90
Gunathilaka and Ekanayake (2015)	Sri Lanka	Indian Basmati	Rice cooker	0.70	64.002)	9.90	1.50	23.90	4.00
		Pakistani Basmati	Rice cooker	0.60	63.002)	9.40	1.40	25.60	2.90
Aldya (2014)	Indonesia	Analog rice (cooked with hot water)	Rice cooker	0.41	53.852)	5.74	4.74	35.26	3.77
Aldya (2014)	Indonesia	Analog rice (cooked with cold water)	Rice cooker	0.42	57.532)	5.79	5.43	30.83	5.50
Orwiantari et al. (2018)	Indonesia	Adan (black rice)	Rice cooker	1.00	54.002)	2.20	0.30	42.50	4.60
Manshur et al. (2018)	Indonesia	IR 64 (white rice)	Rice cooker	0.50	66.822)	3.82	0.39	28.47	1.17
Sari and Rimbawan (2019)	Indonesia	Tarabas Japonica	Rice cooker	0.24	60.022)	4.80	0.70	34.24	0.69
Kabir et al. (2021)	Bangladesh	Nizershai	Rice cooker	1.57	11.60	6.70	2.80	77.33	1.20
		BRRI Dhan 29	Rice cooker	1.43	11.30	6.99	1.90	78.38	1.20
		Chinigura	Rice cooker	1.38	12.30	6.24	2.30	77.78	1.30
		Kalijira hybrid Jira	Rice cooker	1.02	12.80	7.10	2.31	76.77	0.90
		Dhan 12	Rice cooker	1.29	12.50	6.69	2.10	77.42	1.00
		Sworna	Rice cooker	1.81	13.80	8.80	4.12	71.47	1.40
Pipil et al. (2024)	Bangladesh	Indonesian black rice	Rice cooker	1.41	10.64	7.61	3.20	77.14	4.32
		Philippines black rice	Rice cooker	1.33	11.07	8.89	2.15	76.56	4.70
		Vietnamese black rice	Rice cooker	1.55	11.96	7.15	1.57	76.78	4.83
		ACI rice	Rice cooker	1.21	12.50	7.30	1.03	78.96	1.21
Modern cooking methods: pressure cooker
Meera et al. (2019)	India	Kattuyanam (brown rice)	Pressure cooker	1.29	11.93	12.64	1.69	72.45	9.33
		Kavuni (red rice)	Pressure cooker	1.51	10.90	11.81	1.51	74.27	7.04
		Kavuni (black rice)	Pressure cooker	1.75	9.00	13.20	2.05	74.00	11.88
		Karudan Samba (white rice)	Pressure cooker	1.74	11.35	10.98	1.74	74.19	7.87
Modern cooking methods: microwave
Gunathilaka and Ekanayake (2015)	Sri Lanka	Indian Basmati	Microwave	0.70	64.002)	9.90	1.50	23.90	4.00
		Pakistani Basmati	Microwave	0.60	63.002)	9.40	1.40	25.60	2.90

Carbohydrate values were calculated using the difference method for analytical consistency across studies.

¹⁾Studies with substantial nutritional data (≥80% of core nutritional fields completed).

²⁾Moisture content reported on a wet basis

MD, milling degree; ACI rice, low glycemic index rice as a control.

Similarly, the fat content varies in a wide range across different rice varieties, from as low as 0.17% (Syadiah and Rimbawan, 2010) to as high as 6.00% (Arachchilage and Ekanayake, 2024). For example, Fatema et al. (2010) reported fat contents of 1.97%, 2.35%, and 1.75% for BR-14, BR-29, and BR-44 rice varieties, respectively, all prepared via boiling. Pipil et al. (2024) found that rice varieties from Indonesia, the Philippines, and Vietnam cooked in a rice cooker contain 3.20%, 2.15%, and 1.57% fat, respectively. These variations in fat content were primarily attributed to differences between rice varieties and their growing conditions rather than the cooking method employed (Pipil et al., 2024).

The moisture content of cooked rice, which greatly affects its texture and palatability, also considerably varies depending on the preparation method. Arachchilage and Ekanayake (2024) reported moisture contents ranging from 55.9% to 70.6% for various types of cooked rice from Sri Lanka. This considerable variation highlights that cooking techniques can dramatically alter not only the nutritional content but also the sensory qualities of the final product.

The content of carbohydrates, the predominant macronutrient in rice, is also affected by both pre-processing methods and cooking techniques. Table 1 shows parboiling significantly concentrates carbohydrates during pre-processing, with values ranging from 78.96% to 80.36% across different varieties. The effects of parboiling are particularly notable. Widowati et al. (2009) found that the carbohydrate level is consistently above 78% in parboiled rice, which is explained by the specifics of the process. During parboiling, rice undergoes partial gelatinization and loses moisture, which increases the carbohydrate content. Among cooking techniques, rice cooked in a rice cooker exhibits more moderate carbohydrate contents, typically ranging from 71.47%－78.96% on a dry basis. Pipil et al. (2024) also noticed that black rice varieties from different countries cooked in a rice cooker all show similar carbohydrate levels (around 76%－77%), suggesting that this method produces consistent results for similar rice types. Temperature also affects the outcome. Particularly, Aldya (2014) reported that cooking in hot water for 15 min retains more carbohydrates (35.26%) than cooking in cold water for 60 min (30.83%). This difference matters for people monitoring their carbohydrate intake, whether for athletic performance or health reasons.

Analysis of multiple studies revealed substantial variability in fiber content among different rice varieties and cooking methods. Trinidad et al. (2013) found that brown rice varieties typically contain more dietary fiber than white rice varieties. The IMS 2 rice variety prepared in a rice cooker exhibits a dietary fiber content of 2.1% (dry base), whereas brown rice varieties, such as Sinandomeng brown rice and IR64 brown rice, show notably higher fiber contents, 5.0% and 5.9% (dry base), respectively. Meera et al. (2019) presented detailed information on the fiber content of different rice varieties, indicating elevated levels of total dietary fiber in black rice.

Micronutrient content

Although macronutrients frequently dominate dietary discourse, micronutrients are equally vital for overall health. The mineral composition of rice (its ash content) can be preserved to varying degrees depending on the utilized cooking technique. Meera et al. (2019) identified ash contents of 1.29%－1.75% in various pressure-cooked rice varieties from India. This indicates that pressure cooking may be an efficient technique for preserving essential micronutrients.

Bioactive compounds

The impact of cooking methods on rice antioxidant profiles is an emerging research area, with studies demonstrating that specific cooking techniques can enhance or preserve the radical scavenging capacity of various rice varieties (Adedayo et al., 2018). As detailed in Table 2, pigmented rice varieties, including red and black rice cultivars, consistently exhibit higher antioxidant contents than white rice varieties (Meera et al., 2019). In a comprehensive investigation, Meera et al. (2019) quantitatively analyzed the contents of bioactive compounds, including the total contents of phenols, flavonoids, and tannins, as well as the 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity, across different rice varieties and cooking methods.

Table 2.

Effects of cooking methods on the levels of bioactive compounds in rice

Reference	Country	Rice variety	Cooking method	Total phenolic content	Flavonoids (mg CE/g)	DPPH (%)	Tannins (mg TAE/g)
Traditional cooking methods: boiling
Panlasigui and Thompson (2006)	Canada	IR 42 (red rice)	Boiling	70 mg/100 g	n/a	n/a	n/a
		IR 42 (white rice)	Boiling	40 mg/100 g	n/a	n/a	n/a
Modern cooking methods: pressure cooker
Meera et al. (2019)	India	Kattuyanam (brown rice)	Pressure cooking	5.99 mg GAE/g	71.10	99.45	0.71
		Kavuni (red rice)	Pressure cooking	5.89 mg GAE/g	84.40	99.52	0.53
		Kavuni (black rice)	Pressure cooking	3.33 mg GAE/g	44.08	95.48	0.34
		Karudan Samba (white rice)	Pressure cooking	1.91 mg GAE/g	42.33	82.56	0.52

Total phenolic content expressed as mg/100 g fresh weight basis; total phenolic content expressed as mg GAE/g (gallic acid equivalent per gram) dry weight basis. Direct comparison between studies is limited because of differences in analytical methods and measurement units.

CE, catechin equivalent; DPPH, 2,2-diphenyl-1-picrylhydrazyl; TAE, tannic acid equivalent; n/a, not avalaible.

The findings presented in Table 2, while limited to two comprehensive studies, reveal consistent patterns indicating that pigmented rice varieties, particularly red and black rice, typically possess substantially higher antioxidant concentrations than white rice varieties. These elevated antioxidant levels may confer additional health benefits for consumers, including enhanced protection against oxidative stress and reduced risk of chronic diseases. The pressure cooking method employed in these studies appears to effectively preserve these beneficial compounds, although additional research is needed to establish the optimal cooking parameters for maximizing antioxidant retention across diverse rice varieties.

Effect of cooking method on the GI of rice

The GI results presented in Table 3 reveal a complex interplay between rice varieties, cooking methods, and geographical origins. A comprehensive study on various brown rice varieties from Thailand showed substantial variations in GI depending on the cooking method (Chapagai et al., 2016). For most rice varieties, pressure cooking was found to produce consistently lower GI values than preparation in a rice cooker: Chiang (58 vs. 65), Sungyod (72 vs. 81), Lepnok (59 vs. 62), and long grain specialty 1 (64 vs. 73). The only exception was long grain specialty 2 (72 vs. 65). This anomaly suggests that the relationship between the cooking method and GI is not uniform across all rice varieties, warranting further investigation. The use of a smaller sample size (25 g vs. the standard 50 g in most other studies) might have also affected the results.

Table 3.

GI and amylose content of cooked rice depending on rice variety and cooking method

Reference	Country	Rice variety	Cooking method	Amylose content (%)	GI	GI category
Traditional cooking methods: parboiling
Widowati et al. (2009)	Indonesia	Sintanur	Parboiled	20.32	76.32	High
		Gilirang	Parboiled	19.35	72.95	High
		IR 64 (white rice)	Parboiled	24.64	44.22	Low
		Mekongga	Parboiled	25.34	51.99	Low
Widowati et al. (2009)	Indonesia	Ciherang	Parboiled	23.66	61.91	Medium
		IR 42 (white rice)	Parboiled	27.25	46.32	Low
		Batang Lembang	Parboiled	26.59	46.32	Low
Tresnandiati et al. (2019)	Indonesia	Adan (black rice)	Parboiled	32.00	63.00	Medium
Traditional cooking methods: boiling
Panlasigui and Thompson (2006)	Canada	IR 42 (red rice)	Boiled	29.10	82.62	High
		IR 42 (white rice)	Boiled	29.50	94.00	High
Fatema et al. (2010)	Bangladesh	BR-14	Boiled	27.00	54.50	Low
Fatema et al. (2010)	Bangladesh	BR-29	Boiled	29.40	50.30	Low
		BR-44	Boiled	27.20	43.10	Low
Rusda (2019)	Indonesia	IR 64 (white rice)	Boiled	n/a	63.23	Medium
Purbowati and Kumalasari (2023)	Indonesia	IR 64 (white rice)	Parboiled	n/a	21.60	Low
Arachchilage and Ekanayake (2024)	Sri Lanka	Pokkali	Boiled	32.30	53.00	Low
		Murugakayan	Boiled	29.10	63.00	Medium
		Rathdel	Boiled	34.50	51.00	Low
		Madhatawalu	Boiled	33.60	56.00	Medium
		Kuruluthuda	Boiled	27.40	64.00	Medium
		Pachchaperumal	Boiled	35.70	49.00	Low
		Suduheenati	Boiled	33.30	55.00	Medium
		Suwadel	Boiled	26.20	60.00	Medium
		Kaluheenati	Boiled	33.50	61.00	Medium
		Mavee	Boiled	32.60	60.00	Medium
		Masuran	Boiled	30.20	67.00	Medium
		Gonabaru	Boiled	27.20	63.00	Medium
		Kahawanu	Boiled	24.20	56.00	Medium
		Kahamala	Boiled	32.90	54.00	Low
		Hetadawee	Boiled	31.50	51.00	Low
		Behetheenati	Boiled	27.00	58.00	Medium
Traditional cooking methods: steaming
Tresnandiati et al. (2019)	Indonesia	Adan (black rice)	Steamed	28.00	69.00	Medium
Khoiriyyah (2019)	Indonesia	Aek Sibundong (red rice)	Steamed	n/a	40.10	Low
Modern cooking methods: rice cooker
Syadiah and Rimbawan (2010)	Indonesia	Ciherang	Rice cooker	n/a	94.00	High
Trinidad et al. (2013)	Philipines	IMS 2	Rice cooker	0.60	63.00	Medium
		Sinandomeng	Rice cooker	12.60	75.00	High
		NSIC Rc160	Rice cooker	15.30	70.00	High
		PSB Rc18	Rice cooker	18.00	59.00	Medium
		IR 64 (white rice)	Rice cooker	22.90	57.00	Medium
		PSB Rc12	Rice cooker	21.00	63.00	Medium
		PSB Rc10	Rice cooker	27.00	50.00	Low
		Sinandomeng (brown rice)	Rice cooker	12.10	55.00	Medium
		IR 64 (brown rice)	Rice cooker	22.00	51.00	Low
Gunathilaka and Ekanayake (2015)	Sri Lanka	Indian Basmati	Rice cooker	25.50	54.00	Low
		Pakistani Basmati	Rice cooker	25.10	64.00	Medium
Aldya (2014)	Indonesia	Analog white rice (cooked with hot water)	Rice cooker	n/a	55.16	Medium
	Indonesia	Analog white rice (cooked with cold water)	Rice cooker	n/a	51.76	Low
Chapagai et al. (2016)	Thailand	Chiang (brown rice)	Rice cooker	n/a	65.00	Medium
		Sungyod (brown rice)	Rice cooker	n/a	72.00	High
		Lepnok (brown rice)	Rice cooker	n/a	62.00	Medium
		LS 1 (brown rice)	Rice cooker	n/a	64.00	Medium
		LS 2 (brown rice)	Rice cooker	n/a	72.00	High
Orwiantari et al. (2018)	Indonesia	Adan (black rice)	Rice cooker	21.80	57.75	Medium
Manshur et al. (2018)	Indonesia	IR 64 (white rice)	Rice cooker	n/a	75.00	High
Erico et al. (2018)	Indonesia	Mayang Pandan MD 0%	Rice cooker	30.31	55.00	Medium
		Mayang Pandan MD 80%	Rice cooker	36.38	61.00	Medium
Rusda (2019)	Indonesia	IR 64 (white rice)	Rice cooker	n/a	68.17	Medium
Khoiriyyah (2019)	Indonesia	Aek Sibundong (red rice)	Rice cooker	n/a	51.60	Low
Sari and Rimbawan (2019)	Indonesia	Tarabas Japonica	Rice cooker	17.73	79.30	High
Mutiyani et al. (2020)	Indonesia	Organic red rice N790	Rice cooker	n/a	70.17	High
		Organic black rice N790	Rice cooker	n/a	83.83	High
		Organic brown rice N790	Rice cooker	n/a	51.09	Low
		Organic white rice N790	Rice cooker	n/a	72.84	High
Azam et al. (2020)	India	Sampada	Rice cooker	22.82	56.38	Medium
		Dhanrasi	Rice cooker	26.00	59.23	Medium
		DRR Dhan 42	Rice cooker	24.30	71.73	High
		DRR Dhan 43	Rice cooker	23.60	87.40	High
		Jarava	Rice cooker	25.02	94.05	High
Kabir et al. (2021)	Bangladesh	Nizershai	Rice cooker	n/a	59.70	Medium
		BRRI Dhan 29	Rice cooker	n/a	50.50	Low
		Chinigura	Rice cooker	n/a	57.80	Medium
		Kalijira hybrid Jira	Rice cooker	n/a	51.30	Low
		Dhan 12	Rice cooker	n/a	56.90	Medium
		Sworna	Rice cooker	n/a	44.60	Low
Purbowati and Kumalasari (2023)	Indonesia	IR 64 (white rice)	Rice cooker	n/a	22.90	Low
Pipil et al. (2024)	Bangladesh	Indonesian black rice	Rice cooker	19.42	67.23	Medium
		Philipines black rice	Rice cooker	21.77	54.19	Low
		Vietnamese black rice	Rice cooker	28.50	52.64	Low
		ACI rice	Rice cooker	27.52	53.50	low
Modern cooking methods: pressure cooker
Chapagai et al. (2016)	Thailand	Chiang (brown rice)	Pressure cooker	n/a	58.00	Medium
		Sungyod (brown rice)	Pressure cooker	n/a	81.00	High
		Lepnok (brown rice)	Pressure cooker	n/a	59.00	Medium
		LS 1 (brown rice)	Pressure cooker	n/a	73.00	High
		LS 2 (brown rice)	Pressure cooker	n/a	65.00	Medium
Meera et al. (2019)	India	Kattuyanam (brown rice)	Pressure cooker	21.80	47.19	Low
		Kavuni (red rice)	Pressure cooker	n/a	61.69	Medium
		Kavuni (black rice)	Pressure cooker	30.31	56.27	Medium
		Karudan Samba (white rice)	Pressure cooker	36.38	69.74	High
Modern cooking methods: microwave
Gunathilaka and Ekanayake (2015)	Sri Lanka	Indian Basmati	Microwave	25.50	43.00	Low
		Pakistani Basmati	Microwave	25.10	56.00	Medium

GI categories: Low (<55), Medium (55－69), High (≥70) per ISO 26642:2010.

GI, glycemic index; LS, long grain specialty; MD, milling degree; ACI rice, low glycemic index rice as a control; n/a, not avalaible.

Another important aspect is the impact of cooking methods on the amylose content of rice, a crucial determinant of its GI and texture. Chapagai et al. (2016) found that for several varieties of brown rice, pressure cooking typically yields lower amylose levels than preparation in a rice cooker. This discovery is relevant for individuals who want to regulate blood glucose levels or desire particular textural attributes in their cooked rice. The impact of cooking on the amylose content varies among different rice varieties. Erico et al. (2018) noted an increased amylose concentration in Mayang Pandan rice after a certain level of starch gelatinization. The varied outcomes underscore the complex relationship between rice variety and cooking technique, necessitating customized cooking methods to attain optimal nutritional results.

International studies further illuminate the complexity of the relationship between rice GI and cooking method. Particularly, Gunathilaka and Ekanayake (2015) discovered that microwave cooking results in substantially lower GI values than preparation in a rice cooker for both Indian (42 vs. 54, respectively) and Pakistani Basmati rice (56 vs. 64, respectively). This difference highlights the potential of microwave cooking as an effective strategy for reducing the glycemic impact of rice, although the mechanisms underlying this effect require further elucidation.

The Indonesian research contributions show varied results across different rice varieties and cooking methods, as documented in Table 3. Rusda (2019) reported that for the IR 64 rice, boiling results in a lower GI (63.23) than preparation in a rice cooker (68.17), whereas Purbowati and Kumalasari (2023) observed minimal differences in GI between the traditional “aron” method (21.6) and preparation in a rice cooker (22.9) for the same IR 64 variety. The dramatic disparity in GI values between these studies, despite the use of the same rice variety, raises important questions regarding potential methodological differences or additional factors affecting GI measurements, warranting systematic investigation. Tresnandiati et al. (2019) observed that for Adan black rice, steaming results in a higher GI (69) than the traditional “aron” method (63), indicating notable variations in glycemic response even among traditional cooking methods.

Across multiple studies, preparation in a rice cooker showed the greatest impact on rice GI. Investigations by Mutiyani et al. (2020) and Pipil et al. (2024) consistently reported higher GI values for rice cooker-prepared samples than for samples cooked using traditional methods. For various rice varieties prepared in a rice cooker, GI values ranged from 52.64 to 83.83, as detailed in Table 3. The higher GI is likely attributable to enhanced starch gelatinization, resulting in increased carbohydrate accessibility and digestibility. At the same time, Pipil et al. (2024) reported amylose contents ranging from 19.42% to 28.50% in rice cooker-prepared samples, suggesting that the effect on amylose content may be variety-dependent.

Studies on pressure-cooked rice, such as those by Meera et al. (2019) and Chapagai et al. (2016), revealed interesting trends. Pressure cooking generally resulted in good nutrient retention, with protein contents ranging from 10.98% to 13.20% (Meera et al., 2019). This method also well preserved antioxidants and phenolic compounds. However, its effect on GI varies, with some studies reporting lower GI values than for rice cooker-prepared samples while others indicate similar or slightly higher values. Chapagai et al. (2016) found that for multiple brown rice varieties, pressure cooking generally results in lower GI values than preparation in a rice cooker.

Despite the substantial body of evidence on glycemic responses presented in Table 3 and 4, a critical limitation emerges across all included studies. GI measurements in the reviewed studies were conducted exclusively in healthy subjects, with no clinical studies involving diabetic patients identified. This indicates a considerable gap between the stated research objectives and the available evidence. The metabolic responses in diabetic individuals may notably differ from those in healthy individuals because of differences in glucose metabolism and insulin sensitivity. Therefore, the use of these GI findings for making recommendations to diabetic patients requires considerable caution. Although these results provide valuable mechanistic insights from healthy populations, clinical validation in diabetic patients remains essential before therapeutic recommendations can be established.

Table 4.

Starch digestibility, amylose content, and GI of rice prepared using traditional and modern cooking methods

Reference	Country	Rice variety	Starch digestibility (g/100 g)	Amylose content (%)	GI	GI category
Traditional cooking methods: parboiling
Widowati et al. (2009)	Indonesia	Sintanur	36.41	20.32	76.32	High
		Gilirang	37.25	19.35	72.95	High
		IR 64 (white rice)	39.43	24.64	44.22	Low
		Mekongga	39.06	25.34	51.99	Low
		Ciherang	35.52	23.66	61.91	Medium
		IR 42 (white rice)	48.47	27.25	46.32	Low
		Batang Lembang	49.74	26.59	46.32	Low
Modern cooking methods: rice cooker
Erico et al. (2018)	Indonesia	Mayang Pandan MD 0%	45.05	30.31	55.00	Low
		Mayang Pandan MD 80%	47.50	36.38	61.00	Medium

Data limited to studies reporting quantitative starch digestibility measurements.

GI categories: Low (<55), Medium (55－69), High (≥70) based on ISO 26642:2010.

GI, glycemic index; MD, milling degree.

Traditional cooking techniques, particularly with the parboiling pre-processing method and steaming, are generally superior to modern methods, such as pressure cooking or preparation in an electric rice cooker, in preserving nutrients and reducing GI (Table 4). Parboiling rice prior to final cooking has been shown to considerably lower the GI of the final product (Widowati et al., 2009; Penlioglou et al., 2021). This effect was attributed to the formation of resistant starch during parboiling, reducing the digestibility of starch in rice and slowing subsequent glucose absorption. The relationship between parboiling intensity and GI reduction is particularly pronounced, as demonstrated by Islam et al. (2002), who showed that parboiling increases the gelatinization temperature of rice proportionally to the intensity of heat treatment. This tendency is particularly pronounced in pressure parboiling, with the largest GI reduction observed in high-amylose rice varieties (Zavareze et al., 2010).

Steamed rice contains higher levels of slowly digestible starch and resistant starch than boiled rice, as documented by Mustofa et al. (2024) and Zhang et al. (2024). However, the enhanced glycemic effect of steamed rice is likely explained by increased starch gelatinization occurring during steaming. This observation underscores the complex relationship between food processing techniques and nutritional outcomes, highlighting that dietary recommendations and meal planning strategies must use comprehensive approaches that consider both immediate and long-term health implications.

Effects of the cooking method on the sensory evaluation of rice

Sensory evaluation data presented in Table 5 provide valuable insights into how different cooking methods affect the organoleptic properties of various rice varieties, with direct implications for consumer acceptance and dietary adherence. Aldya (2014) conducted a comprehensive sensory evaluation on rice prepared using two distinct rice cooker-based methods: in hot water with a 15-min standing time versus in cold water with a 60-min standing time. The results revealed notable differences across all the examined sensory attributes. The hot water method performed better than the cold water method in all rice attributes: aroma (3.25 vs. 3.50), texture (3.50 vs. 2.58), color (3.10 vs. 2.88), and flavor (2.78 vs. 2.28). These findings suggest that the initial water temperature and standing time considerably affect the sensory profile of cooked rice, with the hot water method generally producing rice with more favorable sensory characteristics. The superior texture and aroma scores achieved through the hot water method were attributed to greater starch gelatinization and more effective development of aromatic compounds during the shorter, more intensive cooking process.

Table 5.

Sensory evaluation studies

Reference	Country	Rice variety	Cooking method	Sensory evaluation scores
				Aroma	Texture	Color	Flavor
Aldya (2014)	Indonesia	Analog white rice (cooked with hot water)	Rice cooker	3.25	3.50	3.10	2.78
Aldya (2014)	Indonesia	Analog white rice (cooked with cold water)	Rice cooker	3.50	2.58	2.88	2.28
Erico et al. (2018)	Indonesia	Mayang Pandan MD 0%	Rice cooker	4.67	4.27	4.09	4.44
	Indonesia	Mayang Pandan MD 80%	Rice cooker	4.91	4.97	3.47	5.10

Direct comparison between studies is limited due to different rice types (analog against natural rice) and panelist training levels.

Sensory evaluation was conducted by untrained panelists (n=30) in Aldya (2014) and semitrained panelists (n=25) in Erico et al. (2018).

MD, milling degree.

A study by Erico et al. (2018) comprehensively examined the effects of starch gelatinization degree on the sensory characteristics of Mayang Pandan rice from Indonesia, providing crucial insights into the relationship between processing intensity and sensory outcomes. The results indicate that 80% gelatinized rice scored better in most attributes than 0% gelatinized rice, specifically showing improvements in aroma (4.91 vs. 4.67), flavor (5.10 vs. 4.44), texture (4.97 vs. 4.27), and overall acceptability (4.63 vs. 4.43). However, the 0% gelatinized rice scored higher in color (4.09 vs. 3.47), suggesting that extensive gelatinization may negatively impact the visual appeal of cooked rice. These results indicate that the degree of starch gelatinization, which can be precisely controlled through the selection of the cooking method, critically affects the final sensory characteristics of rice.

The interplay between cooking methodology and sensory outcomes becomes particularly relevant when considering aromatic rice varieties like Jasmine and Pandan Wangi-Cianjur. While these cultivars exhibit inherently moderate aroma and taste characteristics, strategic application of gelatinization techniques can substantially enhance their sensory appeal, transforming baseline qualities into more pronounced and desirable attributes through controlled processing approaches.

Although Handoko and Bram (2017) indicated that traditional proximate analysis cannot effectively differentiate rice varieties based on their sensory attributes, the studies by Aldya (2014) and Erico et al. (2018) suggested that various cooking methods can substantially modify these inherent characteristics. This indicates that aromatic rice with optimal sensory characteristics can be produced through the careful balancing between varietal selection and cooking method optimization, with environmental factors such as growing conditions introducing additional complexity into this relationship.

The comprehensive analysis presented in this systematic review reveals that the cooking method considerably affects the nutritional composition, GI, and sensory characteristics of cooked rice. It is evident that traditional cooking approaches, especially parboiling and steaming, lead to better preservation of nutrients and reduced glycemic responses than modern methods, such as pressure cooking or preparation in an electric rice cooker. Notably, parboiling is a particularly promising technique for enhancing the nutritional value of rice while lowering its GI. These effects are attributed to the formation of resistant starch and retrogradation processes that modify the structure and digestibility of starch. The variations in glycemic responses across different rice varieties and cooking methods underscore the need for tailored dietary recommendations, with high-amylose varieties generally exhibiting lower GI values.

These findings carry important implications for nutritional science, food technology, and public health research; however, their clinical applicability remains limited because of the absence of diabetic patient data. Although the elucidation of interaction effects between different cooking methods and rice varieties on the characteristics of cooked rice provides valuable mechanistic insights for the development of rice products with optimized nutritional profiles, clinical validation in diabetic populations is essential before therapeutic applications can be considered. Moreover, the intricate interplay between cooking techniques, rice varieties, and resulting nutritional outcomes emphasizes the necessity of multidisciplinary approaches to improving the nutritional profile of rice-based diets. This knowledge can inform individual dietary choices and broader public health initiatives aimed at reducing the risk of nutrition-related chronic diseases in rice-consuming populations. Ultimately, these insights underscore the importance of the optimization of rice preparation methods for improving nutritional outcomes.

The most urgent research direction identified herein is the randomized controlled trials involving diabetic patients. These studies should examine how different rice cooking methods affect clinical outcomes such as postprandial glucose responses, HbA1c levels, and long-term glycemic control in people with T2DM. Additionally, it should be investigated whether the glycemic benefits observed in healthy subjects translate to meaningful clinical improvements in diabetic patients, given the altered metabolic environment characteristic of diabetes.